Colin P. Laroque, Ph.D., P.Ag.
Sunwapta Lake research site
| 2011 Evaluation
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GENS 3401 - Research Methods in Environmental Science -
My research interests focus on past and future climates in Canada, especially on how they relate to dynamic ecosystem and geomorpholgical processes. My specialization is dendrochronology (tree-ring analysis) and I use dendrochronological techniques to gain an understanding about past climates, past glacier activity and extent, past ecosystem dynamics, and even past human activities through dendroarchaeological and dendrochemical investigations.
I began my research career in 1991 studying glacial activity in the Kananaskis Front Ranges region of southwestern Alberta, and have continued my field studies in every year since. I have studied in many alpine regions including the Insular Mountain range of Vancouver Island, the Coastal Mountains of British Columbia, and in many areas of the Monashee, Selkirk, Purcell, and Main Ranges of the Canadian Rocky Mountains in British Columbia and Alberta.
From 1995 to 2003 I was closely associated with the University of Victoria Tree-Ring Laboratory (UVTRL) in the Department of Geography at the University of Victoria. I have completed my two postgraduate degrees through the UVTRL, and have been involved in a number of other projects under the auspices of the lab.
In the fall of 2003 I moved to Mount Allison University, where I set up the first dendrochronology laboratory in Atlantic Canada. The Mount Allison Dendrochronology Lab was formed in January of 2004 and concentrated its research efforts in the 4 Atlantic Canadian provinces. In 2014 I moved the MAD Lab to the University of Saskatchewan (MAD Lab). I urge you to visit the MAD Lab website to see what we are curently up to. I am also the webmaster for the CanDendro group. Please feel free to check out the website to see links to dendrochronological sites in Canada,the Canadian bibliographic database, or simply to find links to dendrochronologists in Canada.
|Abstracts for Publications|
|Davis, E.L., Laroque, C.P., and Van Rees, K.,, 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 traditiional 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 stuiability 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 duture 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 Manitobia maple, and initla results suggest that all species have the ptoential 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 frowin 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. |
Context: Sites whre 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.
|Trisalyn A. Nelson, Laroque, C.P., and Dan J. Smith, 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.
|Mariana Trindade, Trevor Bell , 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.
|Felicia Pickard, AndrÈ Robichaud 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.
Hannah C. MacDonald, Laroque, C.P., David E.B. Fleming and Mihai R. Gherase, 2011. Dendroanalysis of metal pollution from the Sydney Steel Plant in Sydney, Nova Scotia. Dendrochronologia, 29:9-15.
|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 east- ern 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 biocli- matic 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. |
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 (nonhost) were used to establish a hostñnonhost analysis of past sawfly outbreaks on a regional scale. Both re- gional 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.
|M. Trindade 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.
|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.
|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.
|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 Canadaís 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. GÈographie 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.
|Abstracts for Theses |
Laroque, C.P., 2002. Dendroclimatic Response of High-Elevation Conifers, Vancouver Island, British Columbia. Ph.D. Dissertation, University of Victoria, Victoria, British Columbia, 213p.
Using these MAC relationships, proxy information was derived for four climate parameters (April 1 snowpack depth, June-July temperature, July temperature, July precipitation). The explained variance of the models was higher in the two seasonal reconstructions (April 1 snowpack depth r2 = 41 %, June-July temperature r2 = 34 %) than for individual monthly reconstructions (July precipitation r2 = 15 %, July temperature r2 = 24 %). A wavelet analysis showed that each of the four models contains dominant modes of variability throughout time at approximately 16, 32, 65 and 130-150 year periods. Each mode of variability seems to be linked to ocean forcing mechanisms.
Climate/radial-growth relationships were used to predict radial growth under various future climate scenarios. TREE (Tree-ring Radial Expansion Estimator) was developed to present an interactive, internet-based radial-growth model, which calculates the short-term radial-growth response for each tree species to user-defined climate change scenarios. Long-term radial-growth responses were produced using data from general circulation models to develop relationships that predict future radial growth of each tree species. These predictions highlight which species are susceptible to future shifts in climate and indicate which climate parameters may drive changes in radial growth.
|Laroque, C.P., 1995. The Dendrochronology and Dendroclimatology of Yellow-cedar on Vancouver Island, British Columbia. M.Sc. Thesis, University of Victoria, Victoria, British Columbia, 104p.|
The purpose of this study was to investigate the dendrochronological and dendroclimatological potential of yellow-cedar in the Pacific Northwest of North America. A primary objective was to establish whether the growth response of yellow-cedar is sensitive to climate fluctuations. Once it was determined that yellow-cedar was inherently sensitive, further dendroclimatological investigations were attempted.
Trees were sampled at five sites between latitudes 50? and 51? on Vancouver Island. A total of 380 increment cores were collected in the summer of 1994. The samples were subsequently visually cross-dated, prior to ring-width measurement. Site indices were created and the five sites revealed a strong visual and statistical similarity. A regional index was constructed that represents the oldest living chronology for tree growth in Canada.
A response function analysis was initiated to determine the significant climatic parameters to ring growth. This analysis identified previous August temperature as the variable most likely to influence variation in ring width. This variable was used to estimate current August temperature and associated parameters. The chronologies were compared to other relevant research on Vancouver Island and a common climate signal was apparent.
Maintained by Colin P. Laroque
Last updated Dec 13, 2015