Abstracts for Publications

Nehemy, M., Pierrat, Z., Maillet, J., Richardson, A., Stutz, J., Johnson, B., Helgason, W., Barr, A., Laroque, C.P., McDonnell, J. (2023). Phenological assessment of transpiration: The stem-temp approach for determining start and end of season. Agricultural and Forest Meteorology. Volume 331. Doi: 10.1016/j.agrformet.2023.109319.

Field-based assessment of transpiration phenology in boreal tree species is a significant challenge. Here we develop an objective approach that uses stem radius change and its correlation with sapwood temperature to determine the timing of phenological changes in transpiration in mixed evergreen species. We test the stem-temp approach using a five year stem-radius dataset from black spruce (Picea mariana) and jack pine (Pinus banksiana) trees in Saskatchewan (2016–2020). We further compare transpiration phenological transition dates from this approach with tower-based phenological assessment from green chromatic coordinate derived from phenocam images, eddy-covariance-derived evapotranspiration and carbon uptake, tower-based measurements of solar-induced chlorophyll fluorescence and snowmelt timing. The stem-temp approach identified the start and end of four key transpiration phenological phases: (i) the end of temperature-driven cycles indicating the start of biological activity, (ii) the onset of stem rehydration, (iii) the onset of transpiration, and (iv) the end of transpiration-driven cycles. The proposed method is thus useful for characterizing the timing of changes in transpiration phenology and provides information about distinct processes that cannot be assessed with canopy-level phenological measurements alone.

Canning, C., Mood, B., Bonsal, B., Howat, B., Laroque, C.P. (2023). Comparison of tree-growth drought legacies of three shelterbelt species in the Canadian Prairies. Agricultural and Forest Meteorology. Volume 330. Doi: 10.1016/j.agrformet.2023.109317.

Across western Canada, more frequent and severe droughts are expected to occur as a result of climate change. Forests are particularly vulnerable to drought as it often results in mortality events even years following a moisture deficit. Similar events have been observed in Saskatchewan shelterbelts, where many species are planted far outside their native range and are likely more vulnerable to environmental changes. Understanding how common shelterbelt species respond to drought will help landowners make better management decisions under a changing climate. This study looks at how three common shelterbelt species (green ash, Scots pine and white spruce) respond to different drought characteristics (severity, timing, and length) for up to five years following a moisture deficit using superposed epoch analysis. We identified that severe and extreme 3-month droughts greatly impact all three species. However, Scots pine and white spruce tend to recover more rapidly than green ash. Green ash is typically considered one of the most drought tolerant shelterbelt species, but its long recovery times suggest that this may be false. Scots pine was impacted by late summer droughts and white spruce was impacted by June droughts. Both Scots pine and white spruce also saw compensatory growth after their recovery period. This research augments our understanding of how drought characteristics impact three common shelterbelt species in Saskatchewan and how they are likely to recover under more frequent and severe drought events given projected climate change.

Nehemy, M., Maillet, J., Perron, N., Pappas, C., Sonnentag, O., Baltzer, J., Laroque, C.P., McDonnell, J. (2022). Snowmelt water use at transpiration onset: Phenology, isotope tracing, and tree water transit time. Water Resources Research. Volume 58(9). Doi: 10.1029/2022WR032344.

Studies of tree water source partitioning have primarily focused on the growing season. However, little is yet known about the source of transpiration before, during, and after snowmelt when trees rehydrate and recommence transpiration in the spring. This study investigates tree water use during spring snowmelt following tree’s winter stem shrinkage. We document the source of transpiration of three boreal forest tree species—Pinus banksiana, Picea mariana, and Larix laricina—by combining observations of weekly isotopic signatures (δ18O and δ2H) of xylem, soil water, rainfall and snowmelt with measurements of soil moisture dynamics, snow depth and high-resolution temporal measurements of stem radius changes and sap flow. Our data shows that the onset of stem rehydration and transpiration overlaps with snowmelt for evergreens. During rehydration and transpiration onset, xylem water at the canopy reflected a constant pre-melt isotopic signature likely showing late fall conditions. As snowmelt infiltrates the soil and recharges the soil matrix, soil water shows a rapid isotopic shift to depleted-snowmelt water values. While there was an overlap between snowmelt and transpiration timing, xylem and soil water isotopic values did not overlap during transpiration onset. Our data showed 1–2-week delay in the shift in xylem water from pre-melt to clear snowmelt-depleted water signatures in evergreen species. This delay appears to be controlled by tree water transit time that was in the order of 9–18 days. Our study shows that snowmelt is a key source for stem rehydration and transpiration in the boreal forest during spring onset.

Rudd, L., Belcher, K., Kulshreshtha, S., Laroque, C.P., and Bentham, M. (2022). Life cycle assessment of carbon dioxide emissions from shelterbelt seedling production and transportation in Saskatchewan, Canada. American Journal of Agriculture and Forestry. Volume 10(3): 85-93. Doi: 10.11648/j.ajaf.20221003.11

Shelterbelts on Saskatchewan (SK) farms are rows of tree and shrub species established around farmyards and livestock enclosures and within crop fields to serve various roles, including protection against wind and water damage to crops and farm infrastructure, soil erosion and moisture loss. Shelterbelts also can contribute to environmental benefits, most important of which is mitigation of greenhouse gas (GHG) emissions, which has been identified as an important climate change mitigation strategy. In the overall strategy of mitigation of GHGs, there is a need for quantifying emissions of these gases in various mitigation operations, including plating of shelterbelts on farms. In order for a farm to plant a shelterbelt, a seedling has to be produced. This information is not currently available and therefore, was selected as the focus of the study. This research developed a life-cycle assessment of production and transportation of shelterbelt seedlings. It provides details on the processes and emissions of the production and transportation stages in the generation of tree seedlings used to establish a one kilometer long farm shelterbelt. The production and transportation stages for 1,000 shrub shelterbelt seedlings was estimated to generate 2,200 kg of carbon dioxide emissions regardless of species. During these stages of the shelterbelt life-cycle, the primary sources of GHG emissions were energy use for heating and for lighting during seedling growth while transportation of seedlings from the point of production to point of use represented a significantly smaller proportion of overall emissions.

Beckhusen, Gary, Stuart, Glenn, Andrew, Leon, Mackay, Glen, Andrews, Thomas, Laroque, Colin. (2022). Creating a Millennial-Long Chronology in Northern Canada: Dendroarchaeological Dating of the Moose Horn Pass Caribou Fence (KjRx-1), Mackenzie Mountains, NT. Forests. Doi: 13.1.10.3390/f13020221

The Moose Horn Pass Caribou Fence site (KjRx-1) consists of three wooden fences located in a remote area of the Mackenzie Mountains in Canada’s Northwest Territories. Situated in the traditional homeland of the Shúhtagot’ine (Mountain Dene), they were used to assist past hunters to harvest northern mountain caribou by channeling multiple animals toward kill zones. The main fence is nearly 800 m in length and terminates in a corral structure after descending from high ground into a valley. The two smaller fences are located north and south of the main fence, and they do not descend into the valley. Standard dendrochronological methods were employed to determine the ages of wood taken from the fence structures. Seventy-five living white spruce (Picea glauca) trees in the area were cored to determine the overall tree-ring growth patterns in the local environment. The chronology of living trees was supplemented by the inclusion of 29 standing-dead trees to establish a longer chronology of dated ring widths. Sixty-two of 89 cross-sections cut from the fence timbers were crossdated and added to the overall chronology, which created a well-replicated chronology of ring-widths from 972 to 2016 C.E. The terminal dates of material from the three fence systems suggest that the complex was built from trees that died over a wide temporal period, spanning the years 1314 to 1876 C.E, with clusters of dates between ca. 1420–1480 and 1580–1750 C.E. The millennial-long chronology developed in this study can now be used as a base to assist in dendroarchaeological dating of many more artifacts from the region.

Nehemy, M.F., Pierrat, Z., Maillet, J., Richardson, A., Stutz, J., Helgason, W., Laroque, C.P., McDonnell, J. (2021). Phenological assessment of boreal forest transpiration. The SAO/NASA Astrophysics Data System, 2021AGUFM.H21I..06N

The timing of vegetation phenological events drives functional changes in forest carbon and water cycles. Quantifying phenological change in the boreal forest is especially important with observed climate change influencing shifts in timing of water availability through snowmelt and observed increased length of growing season. Field-based assessments of transpiration phenology are challenging because they require tower-based observations that often provide start and end of season dates with large uncertainties, and do not allow for species-level assessments of phenological changes. Here we develop a simple and objective metric that relates stem radius change with sapwood temperature to determine the timing of phenological changes in transpiration in a boreal forest setting in Saskatchewan. We test this new metric using a five-year stem radius dataset from black spruce (Picea mariana), jack pine (Pinus banksiana) and larch (Larix laricina). We compared our measured and modeled field-based phenological changes in transpiration against tower-based measurements of green chromatic coordinate (GCC) derived from phenocam images, evapotranspiration measured by the eddy covariance method, and tower-based measurements of solar-induced chlorophyll fluorescence (SIF). Our results showed that our new stem radius-sapwood correlation metric allows a daily assessment of the timing of four transpiration phenological phases: (i) the end-of the freeze thaw cycles indicating the start of the growing season, (ii) the onset of stem rehydration, (iii) the onset of transpiration, and (iv) the end of transpiration-induced cycles indicating the end of the growing season. We observed small to no difference in the timing of stem rehydration and onset of transpiration across the evergreen species. The end of freeze-thaw cycle was in good agreement with the GCC derived 10% greenness rising transition date. Furthermore, the onset of transpiration indicated strong coherence with the GCC derived 25% greenness rising transition date. Our proof of concept of this new metric shows that characterizing the timing of changes in tree hydraulics using stem radius is useful and provides unique information about transpiration phenology that cannot be assessed with tower-based measurements alone.

Maillet, J., Nehemy M.F., Mood, B.J., Pappas, C., Bonsal, B., and Laroque, C.P. (2022). A multi-scale dendroclimatological analysis of four common species in the southern Canadian boreal forest. Dendrochronologia, Volume 72. https://doi.org/10.1016/j.dendro.2022.125936

A comprehensive assessment of the tree growth/climate relationship was undertaken to better understand the potential impacts of climate change on the growth dynamics of four widespread and common boreal tree species, namely jack pine (Pinus banksiana), black spruce (Picea mariana), eastern larch (Larix laricina), and trembling aspen (Populus tremuloides), located at the southern limits of the Canadian boreal forest. Over intra-annual time scales, results show that precipitation is likely the main driver of stem radius change (∆R), with jack pine radius exhibiting the most consistent positive relationship. Precipitation had a stronger relationship with stem radius variation in black spruce and eastern larch during periods when volumetric water content (VWC) in the root zone was below average, pointing to the likelihood that certain species rely more heavily on available moisture in the uppermost layers of the soil column to replenish stem water, especially during extended dry periods. Warm air temperatures had an immediate negative impact on stem water content due to transpiration. This was most marked during periods of reduced moisture availability in the root zone, when trees are more susceptible to net water volume loss. During periods when moisture was not limiting, a positive relationship between lagged air temperature and ∆R was detected. Warm air temperatures may therefore play an important role in stimulating radial growth when moisture requirements are met. At annual temporal resolution, the growth/climate relationship changed over the lifetime of our study species. Over the last several decades, the relationship between precipitation and annual radial tree growth has weakened, while positive relationships between spring and summer air temperature and annual radial tree growth have emerged, likely signaling a decrease in moisture limitations, and a positive response to spring warming. Our findings reveal that boreal forest tree species may benefit from spring and summer warming over the near term, providing there is sufficient moisture to support growth. Over the long term, rates of evapotranspiration are expected to overshadow gains in moisture related to an increase in precipitation. Under these circumstances, we are likely to see reduced growth rates and an increasingly negative response of boreal tree species growth to warm air temperatures.

Amichev, B.T., Laroque, C.P., Van Rees, K.C.J. (2021). Shelterbelt management practices for maximized ecosystem carbon stocks on agricultural landscapes in Saskatchewan, Canada. Environmental Management, Volume 68, page 522-538. https://doi.org/10.1007/s00267-021-01511-9

There is a significant knowledge gap in the area of management of the vast shelterbelt network currently existing on agricultural lands in Canada and across the world. Throughout eight decades of shelterbelt planting in Saskatchewan, Canada, there are no available records of shelterbelt management practices used by land managers, such as herbicides (H), fertilizers (F), irrigation (I), or tillage (T) applications, collectively referred to as HFIT management. The main objective of this large-scale study was to quantify the effects of HFIT management on shelterbelt carbon sequestration for six common tree and shrub species. Field data from 303 randomly selected shelterbelts across millions of hectares of agricultural land in three soil zones were combined with existing shelterbelt carbon stock curves for Saskatchewan, produced by a shelterbelt carbon management support tool, Belt-CaT, to estimate site-specific total ecosystem carbon (TEC) stocks. Estimated TEC stocks and annual rates for HFIT sites were compared to the no management sites used as a reference. HFIT management increased carbon stocks for the majority of species, four of six, resulting in higher TEC at any tree spacing, mostly at higher suitability sites. However, HFIT management effects were not consistent across individual species, land suitability, or planting designs. The top three HFIT management combinations for hybrid poplar were IT, HIT, and HI, for white spruce they were FT, IT, and FIT, and only FT benefited caragana shelterbelts. The lack of management practices makes unmanaged shelterbelts more unpredictable and unreliable, in terms of tree growth and carbon stocks sequestration potential.

Nehemy, M. , Maillet, J. , Laroque, C.P. (2021). Stem radius change from Picea mariana and Larix laricina at the Old Black Spruce site, Boreal Research Ecosystem and Monitoring Sites (BERMS). Federated Research Data Repository. https://doi.org/10.20383/102.0367

This dataset holds stem radius data collected at the Boreal Ecosystem Research and Monitoring Sites (BERMS). Stem radius change was monitored at the Old Black Spruce site (OBS) (53. 98 ºN, 105.12 °W) from the two dominant tree species, black spruce (Picea mariana) and eastern larch (Larix laricina). The stem radius change was measured with the use of circumference band dendrometers, type DC2 and DC3 from Ecomatik (Ecomatik, Germany), and recorded every 30 min using a HOBO UX120-006M data logger. An array composed of four or less dendrometers were affixed to individual trees of the same species and connect to the same data logger. There was a total of eight arrays at OBS, four monitoring 13 P. mariana trees, and four monitoring 13 L. laricina trees. There are periods where data from less dendrometers are available due to logger failure and/or wild animals interfering on measurements. No gap filling technique was used when gaps were present. This dataset includes data that have been processed for analysis. More details on the measurements and data processing can be found in the README file.

B.J. Mood, B. Bonsal, B. Howat, C.P. Laroque, 2021. Multi-year white spruce drought legacies in southern Saskatchewan. Forest Ecology and Management, Volume 49. https://doi.org/10.1016/j.foreco.2021.119144

In many regions across western Canada’s boreal forest, drought impacts on long-term white spruce (Picea glauca (Moench) Voss) radial growth are poorly understood. This is also the case for white spruce shelterbelt trees south of their natural range in agricultural regions of the Canadian Prairies. Understanding how white spruce has responded to drought in the past will be vital for management purposes for those who rely on shelterbelts and will help develop a better understanding of how white spruce in the Canadian Boreal Forest will be impacted by climate change. Using tree-rings, we tested how radial growth responds to different drought magnitudes, time-steps, and timing in southern Saskatchewan during and after droughts. White spruce radial growth is statistically associated to 3-month June-August and July-September Standardized Precipitation-Evapotranspiration Index (SPEI) values. Drought severity has a greater impact on radial growth compared to timing and time-step during the drought year and the five years after. Three-month, extreme droughts from July-September appear to have the greatest overall negative impact on white spruce growth in southern Saskatchewan. Our results indicate that white spruce has a complex multi-year response to varying drought conditions in southern Saskatchewan although the physiological mechanisms behind radial growth changes are yet unknown. This research augments our current understanding of white spruce’s drought-growth relationship and provides new information useful for understanding how the shelterbelts in southern Saskatchewan and the Canadian Boreal Forest may respond to different characteristics of moisture deficit conditions in the future where longer and more pronounced droughts are projected to occur.

Pierrat, M.F., Nehemy, A. Roy, T. Magney, N. Parazoo, C.P. Laroque, C. Pappas. O/ Sonnentag, K Grossman, D. Bowling, U. Seibt, A. Ramirez, B Johnson, W. Hegason, A. Barr, J. Stutz, 2021.Tower-based remote sensing reveals mechanisms behind a two-phased spring transition in a mixed-species boreal forest. Journal of Geophysical Research: Biogeosciences. Volume 126; Volume 5. DOI: 10.1029/2020JG006191.

The boreal forest is a major contributor to the global climate system, therefore, reducing uncertainties in how the forest will respond to a changing climate is critical. One source of uncertainty is the timing and drivers of the spring transition. Remote sensing can provide important information on this transition, but persistent foliage greenness, seasonal snow cover, and a high prevalence of mixed forest stands (both deciduous and evergreen species) complicate interpretation of these signals. We collected tower-based remotely sensed data (reflectance-based vegetation indices and Solar-Induced Chlorophyll Fluorescence [SIF]), stem radius measurements, gross primary productivity, and environmental conditions in a boreal mixed forest stand. Evaluation of this data set shows a two-phased spring transition. The first phase is the reactivation of photosynthesis and transpiration in evergreens, marked by an increase in relative SIF, and is triggered by thawed stems, warm air temperatures, and increased available soil moisture. The second phase is a reduction in bulk photoprotective pigments in evergreens, marked by an increase in the Chlorophyll-Carotenoid Index. Deciduous leaf-out occurs during this phase, marked by an increase in all remotely sensed metrics. The second phase is controlled by soil thaw. Our results demonstrate that remote sensing metrics can be used to detect specific physiological changes in boreal tree species during the spring transition. The two-phased transition explains inconsistencies in remote sensing estimates of the timing and drivers of spring recovery. Our results imply that satellite-based observations will improve by using a combination of vegetation indices and SIF, along with species distribution information.

Kröbel, R., Moore, J., Ni, Y., Mcpherson, A., Poppy, L. Soolanayakanahally, R., Amichev, B., Ward, T., Laroque, C.P.,Van Rees, K., Akhter, F., 2020. Demonstration and Testing of the Improved Shelterbelt Component in the Holos Model. Frontiers in
Environmental Science. 8. 10.3389/fenvs.2020.00149.

The shelterbelt component of Canada’s whole-farm model Holos was upgraded from an age-determined to a circumference-determined (at breast height) calculation using a multi-stem averaging approach. The model interface was developed around the idea that a shelterbelt could have multiple rows, and a variable species composition within each row. With this, the model calculates the accumulated aboveground carbon in the standing biomass and a lookup table of modeled tree growth is used to add estimates of the belowground carbon. Going from an initial interface that asks for the current state, the model also incorporates an option of past and future shelterbelt plantings. In order to test the model’s suitability, we measured diverse shelterbelts (evergreen, deciduous, shrub type) in southern Saskatchewan, Canada representing commonly planted woody species. By making use of Caragana, Green Ash, Colorado Spruce, Siberian Elm, and a mixed Caragana/Green Ash tree row, we tested how many tree circumference measurements would be required to yield a representative average. Later, these results were incorporated in the Holos model to estimate the accumulated above-and below-ground carbon in each shelterbelt type.

Amichev, B.T., Laroque, C.P., Belcher, K. W., Bentham, M.J., Van Rees, K.C.J., 2020. Shelterbelt systems establishment in Saskatchewan, Canada: a multi-criteria fuzzy logic approach to land suitability mapping. New Forests, 51: 933-963.

There is lack of guidelines helping land managers to locate suitable areas for planting new shelterbelt agroforestry systems on their landbases. The goal of this study was to create land suitability maps for deciduous, coniferous, and shrub shelterbelt agroforestry systems establishment across a wide range of climatic and soil zones of Saskatchewan, Canada. Spatial shelterbelt data and a suite of 50 predictor variables were analyzed using multivariate principal component analysis (PCA), principal component regression (PCR), fuzzy logic analysis, and GIS mapping techniques. Fifty spatial datasets were used as shelterbelt establishment predictor variables (4 groups): 21 climate (1980–2010 normals), 13 land management, 14 soils, and 2 topographic criteria. A shelterbelt carbon inventory spatial layer was used as the shelterbelt establishment indicator dataset. Using PCA and PCR analyses, the overall importance (cumulative loading: positive or negative) of all predictor variables was determined and used to create shelterbelt suitability maps by means of weighted-sum overlays in GIS. Statistically significant positive correlations between mapped shelterbelt suitability levels and observed mean shelterbelt carbon stocks were used to evaluate the resulting deciduous (4.86 million hectares (Mha) study area; p = 0.0033, R2 = 0.79), coniferous (1.96 Mha; p = 0.0008, R2 = 0.77), and shrub suitability maps (2.06 Mha; p = 0.0002, R2 = 0.83). Additional 8.76, 7.90, and 9.77 Mha were identified as suitable for planting future deciduous, coniferous, and shrub shelterbelt systems, respectively, mapped as above-average or high suitability land. Shelterbelt suitability mapping is a means to delineating and ranking the land across large landscapes. The approach employed in this study can benefit other afforestation and agroforestry adoption studies across Canada and the world.

Amichev, B.Y., Laroque, C.P., Van Rees, K.C.J, 2020. Shelterbelt removals in Saskatchewan, Canada; implications for long-term carbon sequestration. Agroforestry Systems, 94: 1665-1680.

Shelterbelt agroforestry systems represent an actively managed historical agricultural resource for which farmers are the driving force, and their decisions have long-term consequences. For decades, detailed records were maintained of millions of trees and shrubs planted in shelterbelts on agricultural fields and farmyards across the Canadian Prairies. However, no records were collected regarding shelterbelt removals. This study quantified the length and carbon (C) stocks of all removed shelterbelts in Saskatchewan for the 2008–2016 period, and identified shelterbelt removal trends across five soil zones. Removals were detected using a recently developed integrated GIS and remote sensing approach, and were land-use features that were mapped as shelterbelts in an inventory map in 2008 but were missing in the classified map in 2016. A total of 2491.2 km of shelterbelts were removed, containing 190.7 GgC (1 Gg = 1000 Mg = 1000 tonnes). The majority of C stock removals were in shrub shelterbelts (107.2 GgC; 1676.6 km), followed by deciduous (78.1 GgC; 719.1 km) and coniferous shelterbelts (5.4 GgC; 95.5 km). Medium (2–3 rows) and wide (> 3 rows) shelterbelts had higher likelihood of being completely removed, while narrow (1 row) shelterbelts were only shortened. Removals in the < 50 m length designs were one- to three-orders of magnitude higher than any other shelterbelt length design. Future shelterbelt removal studies could serve to sustain the carbon sequestration effectiveness of the existing and extensive shelterbelt network on the Canadian Prairies in the long term, and to protect an important agricultural resource that took a very long time to establish.

Pappas, C., Maillet, J., Rakowski, S., Baltzer, J.L., Barr, A.G., Black, T.A., Fatichi, S., Laroque, C.P., Matheny, A.M., Sonnentag, A.M.O, Zha, T., 2020. Aboveground tree growth is a minor and decoupled fraction of boreal forest carbon input. Agricultural and Forest Meteorology, 290. https://doi.org/10.1016/j.agrformet.2020.108030.

The boreal biome accounts for approximately one third of the terrestrial carbon (C) sink. However, estimates of its individual C pools remain uncertain and are often limited to specific points in time. Here, focusing on the southern edge of the boreal forest in central Canada, we quantified the magnitude and temporal dynamics of C allocation to above-ground tree growth at a mature black spruce (Picea mariana)-dominated forest stand in Saskatchewan. We reconstructed annual total live above-ground tree biomass increment (AGBi) using a biometric approach, i.e., species-specific allometry combined with forest stand characteristics and tree ring widths collected with a C-oriented sampling design. We explored the links between boreal tree growth and ecosystem C input by comparing AGBi with eddy-covariance-derived ecosystem C fluxes from 1999 to 2015. Mean AGBi at the study site was 71 ± 7 g C m-2 (1999-2015), which is only a minor fraction of gross ecosystem production (GEP; i.e., AGBi / GEP ≍ 9 %). Ecosystem C input and AGBi were decoupled, highlighting the potential role of direct sink limitations (temperature, water availability) on boreal tree wood formation. Moreover, C allocation to AGBi remained stable over time, with a temporal trend of near zero (-0.0001 yr-1; p-value=0.775), contrary to significant trends in GEP (+5.72 g C m-2 yr-2; p-value=0.02) and ecosystem C use efficiency (i.e., NPP / GEP; -0.0041 yr-1, p-value=0.007). These findings highlight the importance of below-ground tree C investments, together with the substantial contribution of understory, ground cover and soil to the boreal forest C balance. Our quantitative insights into the magnitude and temporal dynamics of above-ground boreal tree C allocation offer additional observational constraints for terrestrial ecosystem models that, to date, are biased in converting C input to biomass, and can guide forest-management strategies for mitigating carbon dioxide emissions.

Mayrinck, R.C., Laroque, C.P., Amichev, B.Y., Van Rees, K.C.J, 2019. Above- and Below-ground Carbon Sequestration in Shelterbelt Trees in Canada: A Review. Forests, 10(10): 922.

Shelterbelts have been planted around the world for many reasons. Recently, due to increasing awareness of climate change risks, shelterbelt agroforestry systems have received special attention because of the environmental services they provide, including their greenhouse gas (GHG) mitigation potential. This paper aims to discuss shelterbelt history in Canada, and the environmental benefits they provide, focusing on carbon sequestration potential, above- and below-ground. Shelterbelt establishment in Canada dates back to more than a century ago, when their main use was protecting the soil, farm infrastructure and livestock from the elements. As minimal-and no-till systems have become more prevalent among agricultural producers, soil has been less exposed and less vulnerable to wind erosion, so the practice of planting and maintaining shelterbelts has declined in recent decades. In addition, as farm equipment has grown in size to meet the demands of larger landowners, shelterbelts are being removed to increase efficiency and machine maneuverability in the field. This trend of shelterbelt removal prevents shelterbelt’s climate change mitigation potential to be fully achieved. For example, in the last century, shelterbelts have sequestered 4.85 Tg C in Saskatchewan. To increase our understanding of carbon sequestration by shelterbelts, in 2013, the Government of Canada launched the Agricultural Greenhouse Gases Program (AGGP). In five years, 27 million dollars were spent supporting technologies and practices to mitigate GHG release on agricultural land, including understanding shelterbelt carbon sequestration and to encourage planting on farms. All these topics are further explained in this paper as an attempt to inform and promote shelterbelts as a climate change mitigation tool on agricultural lands.

Mamet, S.D., Brown, C.D., Trant, A.J., Laroque, C.P. 2019 Shifting global Larix distributions: northern expansion and southern retraction as species respond to changing climate. Journal of Biogeography 46(1): 30–44.20.

With 181 observations of Larix range limit dynamics, we used five distribution parameters (tree line advance, stand infilling, tree line recession, stand thinning, no response) and their determinants (climate, land use change, natural disturbance) to describe and explain observed patterns of Larix range shifts under contemporary climate change. We ran a redundancy analysis on the matrix of five distribution parameters considered with other climatic and non-climatic parameters as explanatory variables. We also characterized the climatic niche of Larix species (temperature and precipitation) and how the niche has changed during the 20th century. Of 173 sites studied over the full distribution of Larix, 63% experienced Larix population increases, 18% had population decreases, and no response was detected at 19% of sites. Latitudinal Larix tree lines in Siberia and North America appear to be infilling and shifting their distributions northward, whereas Larix recession and thinning was more common in southern regions, suggesting southern populations may be experiencing greater drought stress than their northern counterparts. Climatic niches of most Larix species shifted towards warmer and wetter conditions, with tree line advance/forest infilling in cool/dry climate space, and recession/thinning in warm/dry space. Northern expansion is underway or seems imminent for boreal Larix species, primarily L. laricina in North America. Retraction in southern regions and disappearance of some mountainous populations may be inevitable due to their narrow ecological niches. Species restricted to mountainous habitats may expand locally, though will likely not contribute to broad scale range expansion. These changes will depend on suitable climate, disturbance, and dispersal mechanisms.

Ha, T.V., Amichev, B.Y., Belcher, K.W., Bentham, M.J., Kulshreshtha, S.N., Laroque, C.P., Van Rees, K.C.J, 2019. Shelterbelt Agroforestry Systems Inventory and Removal Analyzed by Object-based Classification of Satellite Data in Saskatchewan, Canada. Canadian Journal of Remote Sensing, 45:2, 246-263.

Shelterbelt agroforestry systems inventory is challenging given their narrow linear feature and extensive distribution. The objective of this study was to evaluate the capability of Sentinel-2A Multispectral Instrument (MSI) and Sentinel-1B Synthetic Aperture Radar (SAR) imagery in (i) delineating shelterbelt tree rows on managed agricultural land in Saskatchewan, Canada, and (ii) detecting shelterbelt removal during the period 2008–2016. Contrast split segmentation for the normalized difference vegetation index and Gaussian filter (line filter) data sets from SAR were used to delineate feature borders. Several feature variables from the spectral bands of MSI were used as inputs for an object-based classification using the random forest classifier. A resulting land cover map, including the linear features of existing shelterbelts, was created with an overall accuracy of 80% and kappa value of 0.69. Shelterbelt change detection analysis using the land cover map (2016) and a legacy shelterbelt inventory map (2008) showed that 354 km of shelterbelts were removed within the study area (1,400 km2), accounting for 29.8% of the total shelterbelt length present in 2008. Our results demonstrated that the combination of Sentinel SAR and MSI imagery can provide sufficient information for mapping future shelterbelt planting, as well as allow the detection of shelterbelt removal.

Nehemy, M.F., Millar, C., Janzen, K., Gaj, M., Laroque, C.P., McDonnell, J.J., 2019. 17O‐excess as a detector for co‐extracted organics in vapor analyses of plant isotope signatures. Rapid Communications in Mass Spectrometry 33:1301–1310.

The stable isotope compositions of hydrogen and oxygen in water (δ2H and δ18O values) have been widely used to investigate plant water sources, but traditional isotopic measurements of plant waters are expensive and labor intensive. Recent work with direct vapor equilibration (DVE) on laser spectroscopy has shown potential to side step limitations imposed by traditional methods. Here, we evaluate DVE analysis of plants with a focus on spectral contamination introduced by organic compounds. We present 17O‐excess as a way of quantifying organic compound interference in DVE. We performed isotopic analysis using the δ2H, δ18O and δ17O values of water on an Off‐Axis Integrated Cavity Output Spectroscopy (IWA‐45EP OA‐ICOS) instrument in vapor mode. We used a set of methanol (MeOH) and ethanol (EtOH) solutions to assess errors in isotope measurements. We evaluated how organic compounds affect the 17O‐excess. DVE was used to measure the isotopic signatures in natural plant material from Pinus banksiana, Picea mariana, and Larix laricina, and soil from boreal forest for comparison with solutions. The 17O‐excess was sensitive to the presence of organic compounds in water. 17O‐excess changed proportionally to the concentration of MeOH per volume of water, resulting in positive values, while EtOH solutions resulted in smaller changes in the 17O‐excess. Soil samples did not show any spectral contamination. Plant samples were spectrally contaminated on the narrow‐band and were enriched in 1H and 16O compared with source water. L. laricina was the only species that did not show any evidence of spectral contamination. Xylem samples that were spectrally contaminated had positive 17O‐excess values. 17O‐excess can be a useful tool to identify spectral contamination and improve DVE plant and soil analysis in the laboratory and in situ. The 17O‐excess flagged the presence of MeOH and EtOH. Adding measurement of δ17O values to traditional measurement of δ2H and δ18O values may shed new light on plant water analysis for source mixing dynamics using DVE.

Furlan-Nehemy, M., and Laroque, C.P., 2018. Tree-ring analysis of larch sawfly (Pristiphora erichsonii (Hartig)) defoliation events and hydrological growth suppression in a peatland. Dendrochronologia, 51; 1-9.

Insect defoliation events are a major forest disturbance in the boreal forest in Canada. Reconstructing previous events are crucial to understanding natural factors that lead to insect defoliation periods, improving our ability to predict future infestations and increasing the reliability of forest management plans and pest control programs. Researchers have often been limited in their ability to draw accurate conclusions regarding the history of larch sawfly (Pristiphora erichsonii (Hartig)) infestation events in North America. It is well known that floods can affect survival of larch sawfly populations, as well as suppress radial growth of eastern larch (Larix laricina (Du Roi) K. Koch) trees. Eastern larch often inhabits peatlands where high water-table levels can lead to a decrease in tree-ring widths. Water-table level increases result in similar radial-growth patterns to when trees are defoliated by larch sawfly, making accurate diagnoses of larch sawfly events a challenge. This fact becomes more accentuated when non-host species used for standard dendroecological analyses (often black spruce (Picea mariana (Mill.) Britton) present an opposite relationship to water-table variability, enhancing chances of drawing erroneous conclusions when using program OUTBREAK.This paper introduces a novel case study to advance the understanding of the complex landscapes where these larch sawfly events are taking place. It stresses the necessity of using upland site s less influenced by the hydrological regime to accurately reconstruct larch sawfly defoliation events. We found that where investigations are taking place solely in peatlands or lowlands, and where they are heavily influenced by hydrological conditions, the use of other lines of evidence such as pale rings and long-term hydrological records are crucial to understand the dynamics in the system. In our case study, program OUTBREAK identified five defoliation events in a peatland and upland site; however, hydrological data and pale ring evidence indicated that the last event identified in the peatland site by the host/non-host analysis was confounded by hydrological growth suppression.

Maillet, J., Laroque, C.P., and Bonsal, B. 2017. A dendroclimatological assessment of shelterbelt trees in a moisture limited environment. Agricultural and Forest Meteorology 37 (2017) 30-38.

The goal of this paper is to apply dendroclimatological methods to the analysis of two commonly planted shelterbelt tree species, Fraxinus pennsylvanica (green ash), and Picea glauca (white spruce), to assess their current relationship with climate and determine how their growth may be affected by climate change in the moisture limited region of southeastern Saskatchewan. Spring precipitation and more importantly spring drought, as represented by the standardized precipitation evapotranspiration index (SPEI), were found to be the most important factors controlling the growth of green ash and white spruce in southeastern Saskatchewan. Furthermore, a breakdown in the radial growth-climate relationship was observed in individuals planted far from their typical native ranges, a potential indication of climate induced stress. Considering these findings, and projections of future climate, it is suggested that conditions beyond the northern limit of the artificial green ash range, and into the boreal forest, may become more suitable for green ash growth, while the southern limit of the artificial white spruce range is expected to recede northward. This information can help guide the management of shelterbelt systems in the Canadian Prairies to ensure they provide maximum practical and ecological benefits for now and into the future.

Amichev, B.Y., Bentham, M.J., Kulshreshtha, S., Laroque, C.P., Piwowar, J.M., and Van Rees, K.C.J. 2016. Carbon sequestration and growth of six common tree and shrub shelterbelts in Saskatchewan, Canada. Canadian Journal of Soil Science, 97(3): 368-381.

Shelterbelts sequester and store atmospheric carbon as a direct result of the growth of trees and thus present an opportunity for climate change mitigation. The objectives of this paper were to quantify the growth characteristics and to estimate the carbon stocks of six common shelterbelt species in Saskatchewan: hybrid poplar, Manitoba maple, Scots pine, white spruce, green ash, and caragana. Growth curves (3PG) and carbon dynamics (CBM-CFS3) modelling approaches were used to simulate shelterbelt growth and to estimate the carbon stocks in 50 439 km shelterbelts containing the six species. Shelterbelt width ranged from 6.3 to 14.0 m, age ranged from 5 to 100 yr, and tree density ranged from 356 to 791 trees ha−1. The r2 of the growth curve equations ranged from 28% to 97%, with <50% root-mean-square error and <30% bias. The total ecosystem carbon stocks of all shelterbelts of the six species in Saskatchewan were 10.8 Tg C (1 Tg C = 1 million Mg C), of which 3.77 Tg C was sequestered in the soil and shelterbelt biomass since 1990. The climate mitigation potential of the six shelterbelt species, ranging from 1.78 to 6.54 Mg C km−1 yr−1, emphasized the important role that trees can have on the agricultural landscape to mitigate greenhouse gases (GHGs). Planting shelterbelt trees and shrubs on agricultural landscapes is an important strategy for mitigating GHGs.

Amichev, B.Y., Bentham, M.J., Kurz, W.A., Laroque, C.P., Kulshreshtha, S., Piwowar, J.M., and Van Rees, K.C.J. 2016. Carbon sequestration by white spruce shelterbelts in Saskatchewan, Canada. Ecological Modelling 325, 35-46.

For more than a century, planted shelterbelts in Saskatchewan, Canada have protected farmyards from the elements, decreased soil erosion, sequestered atmospheric carbon, as well as provided many other ecological functions. It is estimated that there are >60,000 km of planted shelterbelts throughout the province, and considerably more in all of the Canadian Prairies. This paper details the overall process of quantifying and mapping the carbon stocks in white spruce (Picea glauca) shelterbelts planted in Saskatchewan. Shelterbelt data collected from field sampling sites, which were identified by a unique site selection approach, were used to parameterize two models for use in shelterbelt systems; an inde- pendent data set was used to validate model predictions. Shelterbelt tree growth was modeled with the Physiological Principles in Predicting Growth (3PG) model, and carbon flux and stocks in shelterbelts were modeled with the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3). Annual total ecosystem carbon (TEC) flux in white spruce shelterbelts increased one order of magnitude, from −0.33 to 4.4 Mg C km−1 yr−1 , for age 1–25 years, and reached a peak of 5.5 Mg C km−1 yr−1 (age 39 years). An ini- tial soil carbon loss from the shelterbelt, caused by the land-use change, was offset in full by tree growth by age 17, 18, and 21 years for trees planted at 2.0, 3.5, and 5.0 m spacing within a row, respectively. Increase in carbon stocks, after 60 years of growth, was predicted in the litter layer (21.8Mg Ckm−1), below-ground biomass (26.1 Mg C km−1 ), and above-ground biomass (117.6 Mg C km−1 ). Across all the different provincial soils, carbon additions were 106–195 Mg C km−1 in 60-yr-old white spruce shelterbelts. Cumulatively, accounting for eight decades of white spruce shelterbelt planting and tree growth, carbon additions totaled 50,440 Mg C province-wide in 991 km of white spruce shelterbelts. The C additions represented 38% of the province-wide TEC stocks, which totaled 131,750 Mg C. The cumulative carbon storage in all components of planted white spruce shelterbelts far exceeded the initial carbon levels present at the time of shelterbelt planting.

Danek, M., Bell, T., Laroque, C.P. 2015. Some considerations in the reconstruction of lead levels using laser ablation: lessons from the design stage of an urban dendrochemistry study, St. John’s, Canada. Geochronometria 42, 217-231.

Study of soils in St. John’s, Canada showed elevated Pb levels representing a potential exposure risk for young children. Old trees growing in the city present a potential annually-resolved record of Pb levels over past centuries that provides important temporal and spatial dimensions to Pb exposure risk assessment. This paper reports the results of our analytical tests to develop a fast, reliable and cost-efficient method using laser ablation inductively coupled plasma mass spectrometry (LA- ICP-MS) for measuring Pb concentration in annual tree rings from available tree species. Our tests focused on approaches to sample preparation as they affect the laser ablation process, the relative merits of the ablation sampling method, and the response of our available tree species, which have contrasting wood structures, to laser ablation. The range of annual Pb concentrations (ppm) measured for each of the study species were as follows: spruce (0.18–6.42); elm (0.12–7.91); and horse chestnut (0.40–14.09). Our results demonstrate that the cutting procedure for preparing tree cores produced the most consistent Pb concentrations of the three methods, although they each displayed problematic anomalies. The selection of the best laser ablation technique appears to be highly dependent on study species and goals. In general, spot analysis permits detailed and targeted studies of tree-ring structures, but requires careful sampling attention for species with complex wood anatomy. The line scan method is ideal for reconstructing annually resolved element concentrations from trees and to some degree mitigates the complicating issue of intra-ring variability. Horse chestnut was determined to be the best of the available tree species because it exhibited a good response to laser ablation and produced the lowest intra-ring variations in Pb concentration.

Amichev, B.Y., Bentham, M.J., Cerkowniak, D., Kort, J., Kulshreshtha, S., Laroque, C.P., Piwowar, J.M. and Van Rees, K.C.J. 2015. Mapping and quantification of planted tree and shrub shelterbelts in Saskatchewan, Canada. Agroforstry Systems 89, 49-65.

The Government of Canada’s farm assistance programs have affected [80 % of Canada’s agricultural land base. One important program in the Prairie Provinces was the prairie shelterbelt program (PSP). A significant aspect of the PSP was shelterbelt tree planting to protect farmyard infrastructure and reduce soil erosion. The main goal of this paper was to map historical shelterbelt establishment, total expected shelterbelt length, and total expected number of six common planted shelterbelt species: caragana (Caragana arborescens), green ash (Fraxinus pennsylvanica), Manitoba maple (Acer negundo), Scots pine (Pinus sylvestris), white spruce (Picea glauca Monch), and hybrid poplar (Populus spp.). A clustering approach was designed to group all agricultural ecodistricts (106 total) into clusters (31 total) based on their similarity in 42 variables within five soil zones of Saskatchewan. Correlations between trees ordered through the PSP and observed shelterbelt length (across 2.1 Mha cumulative study area) were used for shelterbelt probability mapping. Mapping accuracy of planted shelterbelts was 48–86 %. Total shelterbelt length (of any species) ranged from 322 to 45,231 km for (in descending order) dark brown [ brown [ black [ dark gray [ gray soil zones. Novel decadal time-lapse maps and species-specific shelterbelt maps were produced to capture the progression of shelterbelt establishment for the first time at a province-wide scale which gave a new perspective, in map format, of the expansive impact of the living legacy of the PSP. Shelterbelt data gaps and high priority clusters of agricultural land in Saskatchewan were identified for future shelterbelt research.

Małgorzata D., Bell, T., Laroque, C.P., Diegor, W., Lam, R. and Sylverster, P. 2014. Przykład wykorzystania analizy przyrostów rocznych drzew metodą ablacji laserowej (LA ICP-MS) w badaniach zanieczyszczenia środowiska ołowiem. [Polish with English abstract – Example of an application of tree ring laser ablation analysis (LA ICP-MS) in studies of environmental lead pollution] Studia i Materiały CEPL w Rogowie [Proceedings of the Center for Nature and Forestry Education], volume 40: 265-272.

Study of soils and dust in St. John’s, Canada showed elevated Pb levels representing a potential exposure risk for young children. Old trees growing in the downtown core and former city outskirts present a potential annually-resolved record of Pb levels over past centuries that provides important temporal and spatial dimensions to Pb exposure risk assessment. The study focused on the development of a standard and economical laser ablation procedure for dendrochemical analysis of Pb in old trees. The response of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) on cores from urban tree species with contrasting wood structures prepared using three different techniques (raw, cut and sanded) and sampled by conventional (spot ablation) and novel (line scan ablation) procedures were investigated. Horse chestnut (Aesculus hippocastanum L.) was determined to be the best of the available tree species because it exhibited a good response to laser ablation and produced the lowest intra-ring variations in Pb concentration. Preparation of tree cores using a knife produced the most consistent Pb concentrations compared to results for both sanded and unprocessed cores, suggesting caution in the choice of sample preparation procedures. Line scan ablation proved to be a relatively fast and inexpensive method for the study of Pb concentration in tree rings and provides new opportunities for dendrochemical studies.

Richard, M.G., Laroque, C.P., and Herman, T.B. 2014. Relating annual increments of the endangered Blanding’s turtle plastron growth to climate. Ecology and Evolution, 4: 1972-1980.

This research is the first published study to report a relationship between climate variables and plastron growth increments of turtles, in this case the endangered Nova Scotia Blanding’s turtle (Emydoidea blandingii). We used techniques and software common to the discipline of dendrochronology to successfully crossdate our growth increment data series, to detrend and average our series of 80 immature Blanding’s turtles into one common chronology, and to seek correlations between the chronology and environmental temperature and precipitation variables. Our crossdated chronology had a series intercorrelation of 0.441 (above 99% confidence interval), an average mean sensitivity of 0.293, and an average unfiltered autocorrelation of 0.377. Our master chronology represented increments from 1975 to 2007 (33 years), with index values ranging from a low of 0.688 in 2006, to a high of 1.303 in 1977. Univariate climate response function analysis on mean monthly air temperature and precipitation values revealed a positive correlation with the previous year’s May temperature and current year’s August temperature; a negative correlation with the previous year’s October temperature; and no significant correlation with precipitation. These techniques for determining growth increment response to environmental variables should be applicable to other turtle species and merit further exploration.

Kershaw, G.G.L., Castleden, H. and Laroque, C.P. 2014. Physical geography knowledge mobilization on Indigenous landscapes in Canada: Idle No More? A special call to early career scientists. The Canadian Geographer. DOI: 10.1111/cag.12092.

In Canadian physical geography, the ethical implications of research occurring in Indigenous spaces and places have historically been overlooked (Godlewska and Smith 1994). Physical geographers are beginning to recognize our research takes place in a sensitive social space and that the knowledge we pursue has ethical and moral implications. The Canadian Geographer recently published a special issue (56:2) documenting the many challenges and opportunities of community-based participatory research. Throughout that special edition, the 2010 Tri-Council Policy Statement: Ethical Conduct for Research Involving Humans (TCPS2) was referenced as important in directing a shift towards ethical interactions with Indigenous peoples in research. Drawing on material from the special issue, as well as Chapter 9 of the TCPS2 (dedicated to research involving indigenous peoples), this article chronicles the authors’ experiences in attempting to execute an ethically sound physical geography study in traditional Dene territory in northern Saskatchewan. The viewpoint concludes with thoughts on what bridges and barriers exist when attempting physical geography research sensitive to the ethical responsibilities of working in Indigenous spaces. From our perspective, physical geographers can strengthen the ethical defensibility and overall quality of their research by enhancing communication and involvement with indigenous communities potentially impacted by their findings.

Davis, E.L., Laroque, C.P., and Van Rees, K.C.J., 2013. Evaluating the suitability of nine shelterbelt species for dendrochronoligcal purposes in the Canadian Prairies. Agroforestry Systems, 87:713-727.

Shlterbelts have played an important role in prairie agriculture since the late 1800’s; however, little is known abut how these shelterbelts may be affected by climate change. The objective of this study was to determine if shelterbelt species, which are heavily influced by human activity, express a common radial growth signal within and between trees. The study focused on the annual tree-ring growth of the nine most common species of the Canadian Prairies: Salix acutifolia (Acute willow), Caragana arborescens (caragana, or Siberian pea shrub), Picea pungens (Colorado spruce), Fraxinus pennsulvanica (green ash), Populus sp. (hybrid poplar), Pinus sylvestris (Scots pine), Ulmus pumila (Siberian elm) and Picea glauca (white spruce). Tree core samples were collected near Saskatoon, Saskatchewan using traditional dendrochronological methods. The standardized growth of each species was compared with historical homogenized climate data in order to determine the key monthly climate variables impacted each species. Prior to this analysis, little was known about the stuitability of six of these nine species for dendrochronoligcal purposes. It was found that all species crossdate at a significant levele, and that the three most significantly correlated climate factors are able to account for up to 37% of the annual variation in tree-ring growth. The findings of this study suggest that all nine species are suitable, to varying degrees, for future dendrochronological research in the Canadian Prairies as well as having implications for shelterbelt systems elsewhere in the world. The top four species based on four ranking criteria(interseries correlation, mean sensitivity, climate explanatory power, and commonality) were white spruce, acute willow, caragana, and Manitoba maple, and inital results suggest that all species have the potential to be investigated in greater depth.

Anderson, F., Brunt, J., Cameron, R., Caverhill, B., Clapp, D., Clapp, H., Coulthard, B., Hart, S., Helmer, L., Hubley, S., Hurlburt, D., Imlay, T., Jameson, R., Kidd, P., Laroque, C.P., Marotte, R., Marshall, K., Mitchell, S.C., Neily, T., Nickerson, K., O’Neill, N., Phillips, B., Pross, C., Proulx, G., Reardon, C., Todd, J., and Towers, J., 2012 . Bioblitz of the Lake Rossingnol Wilderness Area. Proceedings of the Nova Scotian Institute of Science, 47:33-57.

The Lake Rossignnol Wilderness Area is a 4100 ha protected area in Queens County, Nova Scotia. In July, 2006, the Protected Areas Branch of Nova Scotia Environment invited 34 scientists, students and volunteers to condunct a four day bioblitz of this little studied protected area. Surveys were conducted for reptiles, fish, vascular plants, fungi, lichens, and bryophytes. Physical and biological attributes of peatlands and dendrochronoligcal studies were also conducted. A total of 294 species were identified during tyhe survey, 285 of which are new records for the Wilderness Area. Dendrochronological analysis suggests trees at the site have been growin in place for at least the last 350 years.

Kershaw, G.G.L., and Laroque, C.P., 2012. The dendroclimatological potential of white birch (Betula papyrifera) in Labrador, Canada. The Northeastern Geographer, 4:28-38.

Sites where trees are at the extreme of their climatological limits are best suited for building climate reconstructions. White birch (Betula papyrifera) are often found in Canada pressing the northern extent of the boreal forest. Aims: This study tests the dendroclimatological potential of white birch near its northern range limit by comparing a master chronology from Labrador City, Newfoundland, Canada (N52.58, W66.55) with temperature and precipitation data from the region. Methods: Twenty trees were sampled twice each and crossdated to create a standardized master chronology. Temperature and precipitation data spanning 1960 – 2008 were compared to a standardized version of the master chronology. Results: Core samples spanned 160 years (1851-2010) with a mean age of 135. Series exhibited high intercorrelation (0.425), mean sensitivity (0.374), and autocorrelation (0.808) values. The standardized chronology exhibited strong correlations with mid-summer temperature, as well as a minor relationship with moisture availibility in the previous summer. Conclusion: The high mean sensitivity is indicative of other regional variance. In comparision to previous dendroclimatological studies in the area, white birch appears to have a less muted climate signal, as evidenced by its strong annual growth correlations with June and July temperature. The weak association with precipitation is indicative of other species in Labrador. This study demonstrates that high-quality dendrochronological data can be attained from white birch trees in the Labrador region and consequently, this species should be recognized as potentially a key indicator of temperature trends in the region.

Hart, S.J., and Laroque, C.P., 2012. Searching for thresholds in climate-radial growth relationships of Engelmann spruce and subalpine for, Jasper National Park, Alberta, Canada. Dendrochronologia, 31:9-15.

The relationship between monthly climate predictors and radial growth of Engelmann spruce (Picea engelmanni Parry) and subalpine fir (Abies lasiocarpa (Hook.) Nutt) were explored using both a standard dendroclimatological approach and a multiple adaptive regressions splines (MARS) framework. Consistent with previous research, the radial growth of fir and spruce was related to temperature variables over the time period of the instrumental record. We identify important temporal instability in the statistical relationships between climate variables and the radial growth of both subalpine fir and Engelmann spruce. Using a 30-year running window, only four of the climate variables related to the radial growth of either spruce or fir did not show a switch in the sign of the correlation. A multiple adaptive regressions spline method was then used to gain insight into thresholds that may relate to radial growth/climate instabilities. Using MARS, we were able to identify knots and non-monotonic relationships between radial growth and climate predictors that may be indicators of ecological thresholds. This combination of dendroclimatic methods provides valuable insight into the complex nonlinear responses that both subalpine fir and Engelmann spruce have been growing under in the past centuries.

Trindade, M., Bell, T., Laroque, C.P., Jacobs, J.D., and Hermanutz, L., 2011. Dendroclimatic response of a coastal alpine treeline: a multispecies perspective from Labrador. Canadian Journal of Forest Research, 41: 469-478.

Coastal alpine forests are highly vulnerable to oceanic climate trends, yet these diverse environmental interac- tions remain poorly understood. We used a multispecies perspective to try to better assess the radial growth response of al- pine treeline species within the Northeast Atlantic region of North America to climate variables using bootstrapped correlation analysis. The four species present, black spruce (Picea mariana (Mill.) B.S.P.), white spruce (Picea glauca (Moench) Voss), balsam fir (Abies balsamea (L.) Mill.), and eastern larch (Larix laricina (Du Roi) K. Koch) were sampled in an effort to capture treeñclimate sensitivity that is representative of this entire alpine treeline. The climateñgrowth rela- tionships of spruce trees were comparable with those reported in other Labrador studies, but spring drought sensitivity as reported for coastal northern white spruce trees was not observed. Rather, high levels of precipitation suggest that drought did not limit the radial growth of any of the four species. The relatively small number of statistically significant correla- tions between monthly climate variables and fir and larch trees suggests that factors other than climate limit their radial growth. The multispecies approach better highlighted the range of species-specific relationships between alpine treeline forests and maritime climates (monthly temperature and precipitation) found at the treeline ecotone.

Nelson, T.A., Laroque, C.P., and Smith, D.J., 2011. Detecting spatial connections within a dendrochronological network on Vancouver Island, British Columbia. Dendrochronologia 29:49-54.

In dendrochronology, temporal patterns in radial growth are considered an expression of historical cli- mate processes that cannot be measured. Dendrochronological networks, developed to characterize the geographical and temporal patterns of tree rings, have additional spatial information that can add to our understanding of historical climate conditions. This paper summarizes the use of spatial autocorrelation statistical tools for quantifying spatial trends in dendrochronological networks. Using this approach it is possible to characterize the spatial nature of the process influencing radial growth trends within a tree-ring network. Using a local or mapable measure of spatial autocorrelation it is possible to locate clusters of similar and extreme radial growth trends in any given year and to characterize the persistence of spatial patterns of growth through time. Applied to a dendrochronological network of yellow-cedar (Chamaecyparis nootkatensis (D. Don) Spach), our results suggest that spatial patterns in extreme growth are most often associated with growth limiting climate processes.

Trindade, M., Bell, T., and Laroque, C.P., 2011. Changing climatic sensitivities of two spruce species across a moisture gradient in Northeastern Canada. Dendrochronologia, 29:25-30.

This paper examines the variability in the relationship between climate and radial growth of black spruce (Picea mariana (Mill.) B.S.P.) and white spruce (Picea glauca (Moench) Voss) trees across central Labrador, Eastern Canada. Using climate-sensitive trees, an 11-year running Pearson correlation is applied to local records to examine the relationship between radial tree growth and climate over the last 50 years and the spatial pattern in this relationship with increasing distance inland from the Labrador Sea. Results indicate that there is a high degree of instability in the climate/tree-ring sensitivity despite an overall statistically significant relationship throughout the instrumental time period (1942 to present). Although some peri- ods of reduced climate sensitivity are coincident with insect outbreaks, others cannot be explained by forest disturbance factors. Spatially, the two sites that are most representative of higher elevation areas have more time-stable climate-growth relationships than those inland or along the coast. The results also suggest that the stability of the relationship may be the result of moisture availability, rapid changes in precipitation and temperature, and site-specificity.

Pickard, F., Robichaud, A., and Laroque, C.P., 2011. Using dendrochronology to date the Val Comeau canoe, New Brunswick and developing an eastern white pine chronology in the Canadian Maritimes. Dendrochronologia, 29:3-8.

This paper examines the dendrochronological analysis that was needed to establish the construction date of the Val Comeau canoe. The canoe was unearthed in northeastern New Brunswick after a large storm hit the area. It is currently housed at the New Brunswick Provincial Museum in Saint John, and had been radiocarbon dated to 440 ± 50 years. After a scanning electron microscope analysis, the species of the canoe wood was determined to be eastern white pine (Pinus strobus L.). A chronology for the white pine species was constructed for New Brunswick using living trees and structures; however, the dates did not extend far enough back in time to overlap the range of radiocarbon dates on the canoe. Another eastern white pine chronology was established for Nova Scotia which included an Acadian sluice whose chronology extended back into the radio carbon date range on the canoe. The Val Comeau canoe was successfully pattern matched against the sluice chronology and dated to a minimum cut date of 1557. Regional white pine chronologies for New Brunswick and Nova Scotia were also developed in the process which will help with future dendrochronological investigations within these regions.

MacDonald, H.C., Laroque, C.P., Fleming, D.E.B, and Gherase, M.R., 2011. Dendroanalysis of metal pollution from the Sydney Steel Plant in Sydney, Nova Scotia. Dendrochronologia, 29:9-15.

Dendroanalysis of metal pollution from the Sydney Steel Plant in Sydney, Nova Scotia. The Sydney Steel Plant emitted toxic pollutants into the local area for almost 100 years. Although no paper record exists of the amount and spatial variability of the pollutants emitted, a natural record exists locked in the annual growth of native tree species in the region. Studies have shown that temperate trees can incorporate local metal pollution into their annual rings, creating a temporal and spatial record of the pollution. Two abundant species were sampled within a 5-km radius of the steel plant site. Using den- drochronology, atomic absorption spectroscopy (AAS) and energy dispersive X-ray fluorescence (EDXRF) on white birch, (Betula papyrifera), and eastern larch, (Larix laricina), a new methodology was developed to determine levels of pollutants in a given year. Atomic absorption spectroscopy did not produce accurate results with the small sample sizes we were able to process, but energy dispersive X-ray fluorescence determined that the hardwood birch better incorporated both lead and zinc into annual rings than the softwood larch. The technique provides an interesting area for further study, because it provides a time efficient and repeatable method of analyzing chemicals stored in wood tissue.

Nishimura, P.H., and Laroque, C.P., 2010. Observed continentality in radial growth-climate relationships in a twelve site network in western Labrador, Canada. Dendrochronologia, 29:17-23.

Despite their suitability for dendroclimatological research, the boreal regions of central and western Labrador remain under-researched. In an attempt to evaluate the growth trends and climatic response of this region’s trees, master chronologies have been developed for its four dominant conifer species. Balsam fir (Abies balsamea (L.) Mill.), white spruce (Picea glauca (Moench) Voss), black spruce (Picea mariana (Mill.) Britton, Sterns, Poggenb.) and eastern larch (Larix laricina (DuRoi) K. Koch) were sampled systematically within a 3Eó4E grid of twelve sites at the intersection of 62EW, 64EW and 66EW longitude, and latitudes 52EN, 53EN, 54EN and 55EN. The two most dominant species at each site were sampled, yield- ing a total of twenty-four master chronologies, all of which reflected a highly significant common signal at each site. The chronologies were subjected to a response function analysis to determine the nature of the growth-climate relationships in the region. Summer temperature proved to be the predominant limiting factor with regard to radial growth at most sites. The onset of the optimum temperature regime, however, varies across the network of sites, revealing evidence of a gradient of continentality in the data. Growth-temperature correlations indicated a significant relationship with July temperature at most eastern sites, while western sites tended to correlate with May, June and August temperatures. Central sites tended to correlate with June-July temperatures. We interpret these results as demonstrating the bioclimatic gradient of change between coastally proximal, maritime-influenced sites and inland, continentally influenced locales. This transition occurs approximately 330 km inland from the open Labrador Sea.  

Quann, S.L., Young, A.B., Laroque C.P., Falcon-Lang, H.J., and Gibling, M.R., 2010. Dendrochronological dating of coal mine workings at Joggins Fossil Cliffs, Nova Scotia, Canada. Atlantic Geology 46:185-194.

Joggins, Nova Scotia, was one of the first places in North America where coal was mined. Dendrochronological methods were employed to date timber pit props preserved within relic coal mine workings on the closely adjacent Fundy and Dirty seams. These remains comprise a system of openings that represent formerly underground mines, now exposed by cliff retreat. Of the seventy-three samples collected, forty-eight were successfully cross-dated into floating chronologies and then compared against a local red spruce (Picea rubens) master chronology, thereby establishing the year in which each individual sample was cut as a live tree where bark was present. Results indicate cutting dates of 1849ñ1875, which are generally consistent with archival records of mining activity. Analysis of the 14 openings al- lows differentiation of two phases of mining. Most openings (1ñ9 and 11ñ12 with cut dates of 1849ñ1868) represent adits driven into the cliff from the beach, and associated levels, which comprise an initial drift mine by the General Mining Association (1865-1871). Dendrochronological dates from trees with bark that precede the opening of this first mine suggest that timber stockpiled from the nearby Joggins Mine (opened 1847) was used in its construction. The remaining openings (10 and 13ñ14 with cut dates of 1873ñ1875) represent a system of levels that comprise part of a later mine dug by the Joggins Coal Mining Company (1872ñ1877). Findings improve knowledge of the Joggins UNESCO World Heritage Site and help refine the regional chronology for future dendrochronological studies.

Nishimura, P.H., and Laroque, C.P., 2010. Tree-ring evidence of larch sawfly outbreaks in western Labrador, Canada. Canadian Journal of Forest Research, 40:1542-1549.

As many insect outbreak reconstructions are typically based on targeted single-site sampling, researchers have often been limited in their ability to draw conclusions about regional trends as opposed to local trends in the data. The results of this paper demonstrate the value of a systematic sampling design when studying spatio-temporal processes that can vary greatly within large continuous areas of forest. Many single-site research programs have been conducted to reconstruct the history of larch sawfly (Pristiphora erichsonii Htg.) outbreaks in the eastern boreal region of North America. However, no such research has yet been conducted in the region of Labrador. In an attempt to illustrate the strength of a systematic gridded sampling protocol over a single-site study, we sampled a 12-site grid in western Labrador. Dominant and codominant species were sampled at each grid point, resulting in 24 master chronologies. Six eastern larch (Larix laricina (Du Roi) K. Koch) chronologies (host) and a regional black spruce (Picea mariana (Mill.) Britton, Sterns, Poggenb.) chronology (non-host) were used to establish a host/non-host analysis of past sawfly outbreaks on a regional scale. Both regional and localized larch sawfly outbreaks were identified, but in general, larch sawfly outbreaks in western Labrador appeared to be spatially synchronous and regional in scale.

Trindade, M., and Laroque, C.P., 2009. Multidisciplinary applications of tree-ring analysis in Newfoundland and Labrador. Ktaqamkuk (Irish Journal of Newfoundland and Labrador Studies), 1: 126-143.

We describe the potential for using many types of tree-ring analyses with particular reference to their application to Newfoundland and Labrador issues. Tree-ring analysis is an inexpensive, non-destructive method of studying a variety of living and dead trees and wooden objects. The adaptability of tree-ring analysis to many sub-disciplines renders this science useful for a number of different methodologies, with the results quickly applied to various interest groups throughout the province. Here, we discuss simple applications of tree-ring analysis to climate change scenarios, the power generation industry, forest ecology and management, parks and tourism, cultural heritage, and history across the province.  We also present an innovative tree-ring sampling strategy that has been established across Newfoundland and Labrador. The sampling grid consists of sampling tree species along lines of 1? latitude and 1? longitude across Newfoundland, and 1? latitude and 2? longitude across the majority of Labrador. This grid is the first of its kind in Canada and will provide the means of exploring spatial characteristics of issues that are particularly significant to Newfoundland and Labrador. We illustrate this through tree-ring analysis and the use of our established grid system, there can be many benefits to Newfoundland and Labrador economic and cultural developments.

Robichaud, A., and Laroque, C.P., 2008. Dendroarchaeology in southwestern Nova Scotia and the construction of a regional red spruce chronology. Tree-Ring Research, 64(1): 17-25.

Dendrochronology studies in Atlantic Canada are rare partly because old-growth forests are scarce making it difficult to establish multiple-century tree-ring chronologies. One approach to overcome this problem is to use tree-ring records found in the wood of historical structures. For our study, the Sinclair Inn in Annapolis Royal, Nova Scotia, was selected for a dendroarchaeological assessment because of its rich and complex history: it resulted from the merging of two early 18th century houses (the Soullard and Skene houses). To date the Sinclair Inn, three other historical structures of a younger age were used to establish an annual ring record in lieu of old-growth forest data. Red spruce (Picea rubens), a dominant tree species in the Maritimes, was the most prominent wood found in the structures and allowed for the creation of a regional red spruce reference chronology extending far enough in the past to cover the supposed period of construction of the Sinclair Inn. Crossdating results indicate cutting dates of 1709 and 1710 for the Skene and Soullard houses respectively, and of 1769 for the inn itself. In the process of dating the structure, a ~200-year old regional floating red spruce chronology (1591-1789) was developed that will further help future dendrochronological investigations in the Maritimes. 

Selig, N., Laroque, C.P., and Marsh, S., 2007. Dendroarchaeological investigations in the Maritimes: A case study of Dorchester House, New Brunswick. Material Culture Review, 66:42-49.

This paper describes a method that allows social scientists to discern, with annual and even subannual precision, the construction dates of structures of historic value. The assignment of construction dates is seen as an instrumental starting point when historical investigators are researching individual buildings. By utilizing dendroarchaeological methods (tree-ring analysis), questions concerning when a structure was built, and who originally built or had the structure built, can be greatly illuminated. Dorchester House is one such example in New Brunswick. Description of the procedures to dendroarchaeologically date the structure are described and the initial date of construction (1821) and subsequent renovations (1859) are put in a better historical context once these dates are ascertained. The complex history of the area and the original lot is put into a much clearer timeline once the two dates are assigned to different sections of the house. The vast array of historical sources that relate to the property assessments and census records can be much more selectively filtered to describe with a higher probability the actual historical facts surrounding Dorchester House. The methods, although not new, could greatly assist research on the many other historical wooden structures in Atlantic Canada and elsewhere that have assumed and/or controversial dates of construction, and that are vulnerable to being lost through fire, demolition, or decomposition. This study highlights the underutilization of dendroarchaeological methods in Canada, and illustrates the utility it has to offer to many historical questions.

Campbell, L.J., and Laroque, C.P., 2007. Decay progression and classification in two old-growth forests in Atlantic Canada. Forest Ecology and Management, 238: 293-301.

This paper investigates the relationship between visually apparent stage of decay of coarse woody debris (CWD) and time since death of decaying balsam fir (Abies balsamea L.) and black spruce (Picea mariana [P. Mill]) in old-growth forests in western Newfoundland and in the Cape Breton Highlands (CBH) of Nova Scotia. These sites are two of the least disturbed old-growth forest locations remaining in Atlantic Canada. In Newfoundland, a total of 42 detrital samples were collected from downed logs and standing snags, of which 36 had their mortality dates determined. In the CBH, 50 detrital samples were collected, of which death dates for 44 samples were obtained. For both sites, samples represented all visually discernable classes of decay. In Newfoundland, these visual decay classes were separated by approximately 17 years for a minimum decay time of 85 years. In CBH, a faster rate of decomposition was apparent, with 12-year classes and a minimum decay time of logs of 60 years. Evidence points toward a climate-driven decay regime in both locations, with the longer time frame evident in Newfoundland thought to result from lower temperatures and fewer snow-free days than in CBH.

Laroque, C.P., and Smith, D.J., 2005. Predicted short-term radial-growth changes of trees based on past climate on Vancouver Island, British Columbia. Dendrochronologia, 22: 163-168.

Biologically-based deterministic multiple regression models are developed to investigate the consequences of future climates on the radial growth response of five high-elevation conifer species on Vancouver Island. Historical climate data and tree ring chronologies are used to establish robust relationships between climate and radial growth. Coupled General Circulation Modelled (CGCM) outputs are then used to provide monthly predictions of future climates from 2000 to 2100 AD. The established historical relationships are projected into the future using the CGCM data to predict radial growth. Results indicate that each species will react individually to predicted changes in climate, with no one dominant radial growth trend established. The most radical changes in the radial-growth behaviour occur within mountain hemlock (Tsuga mertensiana) trees that have adapted to survive in deep snowpack environments, a condition that future predictions highlight as the most susceptible to change. 

Bachrach, T., Jakobsen, K., Kinney, J., Nishimura, P., Reyes, A., Laroque, C.P., and Smith, D.J., 2004. Dendrogeomorphological assessment of movement at Hilda rock glacier, Banff National Park, Canadian Rocky Mountains. Geografiska Annaler A, 86A(1): 1-9.

The results of this dendrogeomorphological study provide evidence of the active movement of Hilda rock glacier, a tongue-shaped rock glacier in the Columbia Icefield region of Banff National Park. Cross-sectional samples were cut from 44 detrital subalpine fir (Abies lasiocarpa (Hook.) Nutt.) and Engelmann spruce (Picea engelmannii Parry) boles killed and buried by debris spilling off the steep distal slope of the rock glacier. The samples were crossdated using locally and regionally developed tree-ring chronologies, and were shown to have been killed between 1576 and 1999. Our results show that Hilda rock glacier has advanced at an average rate of 1.62 cm/year since the late 1790s, with limited evidence of similar rates of activity extending back to the mid-1570s. This rock glacier activity is believed linked to persistent periglacial processes that appear to be independent of the climatic forcing mechanisms known to influence glacier mass balances over the same interval.

Laroque, C.P., and Smith, D.J., 2003. Radial-growth forecasts for five high-elevation conifer species on Vancouver Island, British Columbia. Forest Ecology and Management 183: 313-325.

Biologically-based deterministic multiple regression models are developed to investigate the consequences of future climates on the radial growth response of five high-elevation conifer species on Vancouver Island. Historical climate data and tree ring chronologies are used to establish robust relationships between climate and radial growth. Coupled General Circulation Modelled (CGCM) outputs are then used to provide monthly predictions of future climates from 2000 to 2100 AD. The established historical relationships are projected into the future using the CGCM data to predict radial growth. Results indicate that each species will react individually to predicted changes in climate, with no one dominant radial growth trend established. The most radical changes in the radial-growth behaviour occur within mountain hemlock trees that have adapted to survive in deep snowpack environments, a condition that future predictions highlight as the most susceptible to change.

Laroque, C.P., Lewis, D.H., and Smith, D. J., 2000/01. Treeline dynamics on southern Vancouver Island, British Columbia. Western Geography, 10/11: 43-63.

This paper describes the nature of treeline dynamics and upper-elevation tree establishment patterns on southern Vancouver Island, British Columbia. We examined tree growth, climate and seedling relationships at three upper-elevation locations using standard dendroecological approaches. Our data suggest that this habitat has experienced species-specific pulses of tree establishment that have had a major impact on the character of the local treeline boundaries. The stem data collected within quadrats at Gemini Mountain and Haley Bowl show that seedling establishment within the last three centuries was episodic and linked to historical climatic patterns. Successful mountain hemlock establishment in this setting is restricted to periods characterized by either cool summers and shallow winter snowpacks, or warmer than normal summers and moderately deep snowpacks. The establishment of amabilis and subalpine fir seedlings appears restricted to intervals with cool growing seasons and moderately deep seasonal snowpacks. Episodic seedling establishment in the 20th century has resulted in a gradual infilling of the local treeline and the development of a more structured parkland belt that is expected to have habitat implications for endangered Vancouver Island marmot.

Kellner, A.E., Laroque, C.P., Smith, D.J., and Harestad, A.S., 2000. Chronological dating of high-elevation dead and dying trees on Northern Vancouver Island, British Columbia. Northwest Science, 74: 242-247.

We analysed tree rings to determine the time of death for 18 moribund and dead trees used as roosts by bats on northern Vancouver Island. We crossdated 29 increment core samples with tree-ring chronologies of living trees to estimate when the trees died. After they die, yellow-cedar (Chamaecyparis nootkatensis) trees deteriorate slowly and remain standing for as long as 200 years. In contrast, few western hemlock (Tsuga heterophylla) and western white pine (Pinus monticola) snags persist longer than 100 years. The ages at which our sampled trees died were highly variable, with western white pine, western hemlock, and yellow-cedar exhibiting the narrowest to widest range of ages, respectively. Our findings highlight the long persistence of snags in high-elevation coastal forests and the centuries of ecological service that these trees provide to snag-dependent wildlife.

Carter, R., LeRoy, S., Nelson, T., Laroque, C.P., and Smith, D.J., 1999. Dendroglaciological investigations at Hilda Creek rock glacier, Banff National Park, Canadian Rocky Mountains. GÈographie physique et Quaternaire, 53: 365-371.

 Dendroglaciological techniques are used to provide evidence of historical rock glacier activity at Hilda Creek rock glacier in the Canadian Rockies. The research focuses on the sedimentary apron of the outermost morainal deposit, where excavations in 1997 uncovered six buried tree boles that had been pushed over and entombed by distally spilled debris. Cross-sectional samples crossdated with a local Engelmann spruce tree-ring chronology were shown to have been killed sometime after 1856. Based on the extent of the excavation, the data indicates that Hilda Creek rock glacier has continued to advance along the present ground surface at a rate exceeding 1 cm/year.

Laroque, C.P., and Smith, D.J., 1999. Tree-ring analysis of yellow-cedar (Chamaecyparis nootkatensis) on Vancouver Island, British Columbia. Canadian Journal of Forest Research, 29: 115-123.

Yellow-cedar (Chamaecyparis nootkatensis) are the oldest known coniferous trees in Canada. This paper reports on the first dendrochronological investigation of yellow-cedar trees at montane sites on Vancouver Island. Mature yellow-cedar trees were selected for study at four sites along a 200-km northwest-southeast transect. Trees older than 500 years were common at three of the four sites, with numerous individuals older than 750 years identified. Carefully prepared cores proved well suited for ring-width measurement, with 220 cores from 156 trees included in our final four chronologies. The best replicated segment of the four chronologies (1800-1994 A.D.) show common intervals of reduced radial growth in the 1800s, 1840s, 1860s, 1920s, 1950s, and 1970s. While the relative strength of the between-site signals varies over this interval (r = 0.424 to 0.908), it is apparent that the chronologies share a common radial growth signal. Our efforts to identify the role climate played in this relationship were successful and the results appear to have a dendroecological basis within the annual yellow-cedar growth cycle. Six different temperature and precipitation variables explain 61% of the annual ring width variance. Our results suggest that further dendrochronological and dendroclimatological studies using this long-lived species are warranted.

Smith, D.J., and Laroque, C.P., 1998. Mountain hemlock growth dynamics on Vancouver Island. Northwest Science, 72 (Special Issue 2): 67-70.

Mountain hemlock (Tsuga mertensiana [Bong.] Carr.) trees are a major component of the mountain hemlock biogeoclimatic zone in coastal mountains of British Columbia. These stands are under increasing pressure as timber harvesting extends upwards into the montane, and their successful management requires an understanding of how they will respond to future climatic changes. Previous research showed that climatic changes in the 20th century have initiated enhanced radial growth rates within mountain hemlock stands and resulted in invasions of subalpine meadows throughout the region. While these historical climatic changes appear as beneficial to mountain hemlock populations, there is some concern that if the climate warms as hypothesized, the productivity of mountain hemlock stands may be compromised by a restriction in habitat and regeneration capacity.

Smith, D.J., and Laroque, C.P., 1998. High-elevation dendroclimatic records from Vancouver Island. In: Decoding Canada’s Past: Climate Variations and Biodiversity Change During the Last Millennium. MacIver, D.C. and Meyer, R.E. (eds.). Atmospheric and Environment Services, Downsview, Ontario, 33-44.

This paper summarizes research designed to describe the radial growth response of high-elevation stands of co-occurring mountain hemlock (Tsuga mertensiana) and yellow-cedar (Chamaecyparis nootkatensis) to historical climatic fluctuations. Our findings are based on an assessment of annual growth at timberline sites on Vancouver Island extending 175 km southward from Mt. Cain to Heather Mountain in the Cowichan Lake area. The growth trends of both species show synchronous patterns that potentially provide the basis for regional crossdating. Based on these preliminary interpretations, it is concluded there is considerable potential for high-resolution paleoenvironmental reconstruction on Vancouver Island using dendroclimatological research techniques.

Smith, D.J., and Laroque, C.P., 1996. Dendroglaciological dating of a Little Ice Age glacial advance at Moving Glacier, Vancouver Island, British Columbia. Géographie physique et Quaternaire, 50: 47-55.

Dendrochronological investigations at Moving Glacier provide the first calendar-dating of a Little Ice Age glacier advance on Vancouver Island. In 1931, Moving Glacier was within 30 to 50 m of a distinct trimline and terminal moraine marking its maximum Little Ice Age extent. A reconnaissance of the site in 1993 revealed the presence of sheared in situ stumps and detrital trunks inside the 1931 ice limit. Sampling in 1994 showed the site was covered a mature subalpine forest prior to the glacial advance which overrode the site after 1718 A.D. Following this period of expansion, which saw Moving Glacier expand to its maximum Little Ice Age position after 1818 A.D., the glacier apparently experienced only minimal retreat prior to first being photographed in 1931.

Denton, J.J., Laroque, C.P., Williams, A.E., and Wilson, P.J., 1995. Proglacial sedimentation in the Loss Creek valley, southwestern Vancouver Island, British Columbia. Western Geography, 5: 1-12.

A stratigraphic study was conducted on an exposure located in the lower reaches of Loss Creek on Vancouver Island. Four areas were identified in the 72 m high exposure. The lowest unit is composed of 17 m of laminated clays (Unit 1). The next exposure is a 3 m bed of poorly-sorted sand and gravel with a-b planes dipping toward the valley floor (slumped deposit). These are overlain by 37 m of sand and silt rhythmites (Unit 2), followed by 15 m of trough cross-bedded, coarse sands and gravels, with the beds oriented east to west (Unit 3). The coarsening-upwards sequence is interpreted as a proglacial deposit of lacustrine clays, outwash sands, and braided stream gravels, partly buried by a post-depositional slump. Other deposits at lower elevations and up-valley suggest the area is characterized by a complicated sequence of alternating clay, sand, and gravel layers.
These results do not support past research indicating that a single post-Vashon maximum resurgence of the Juan de Fuca ice lobe formed a 460 m ice dam at the mouth of Loss Creek. It seems more likely that the region experienced multiple sequences of advance and retreat phases. Further research is necessary to fully decipher the complex glacial history of this area.

Lawby, C.P., Smith, D.J, Laroque, C.P., and Brugman, M.M., 1995. Glaciological studies at Rae Glacier, Canadian Rocky Mountains. Physical Geography, 15: 425-441.

Rae Glacier is a small cirque glacier located in the front ranges of the Canadian Rocky Mountains. Between 1990 and 1991 field research was completed to describe the physical glaciology of Rae Glacier and to characterize historical glaciological trends at the site. Ablation and surface movement rates were measured using a network of stakes drilled into the glacier and radio-echo sounding was used to describe local ice depths.
Rae Glacier has experienced a significant loss in size and mass during the historical period due to a lengthy interval of negative mass balance conditions. The glacier has decreased in surface area by over 50% and now contains less than 25% of the ice it did at the end of the last century. Surface ice velocity varied between 1.4-5.4 m in 1990 to 1991. Rates of ice ablation proved to be highly variable, with steeper areas showing up to 50% more ablation. Combined with data on the emergent flow component of the glacier, the ablation data suggest the glacier is presently unable to replenish the amount of ice annually being lost to ablation. The glacier has a lag time of between five to ten years which confirms it is sensitive to climatic fluctuations and responds to changes in mass balance within a very short time. This observation is supported by an estimated response time of 42 years.