PICS Research Results
Briefly describe (within 2-3 sentences) your project/fellowship or internship under each heading. Please use plain language rather than technical, with thegoal of communicating your results to a wide audience. The aim is to demonstrate how your research can help British Columbia (and beyond ifapplicable) take effective action in mitigating and/or adapting to climate change. The emphasis should be on practical outcomes.
For example; a project on predicting extreme precipitation events is helping a city redesign its storm-water drains; research on citizen engagement tools,including social media, is helping to better connect residents' interests and ideas to municipal planning initiatives; and a study on fuel cells has answereda specific question on the technology, which is now contributing to a larger project.
The information you provide is important to the Pacific Institute for Climate Solutions (PICS), and will be used to augment metrics of impact of theInstitute.
Date:
May 20, 2014
Project Title:
Developing environmental-response functions of growth and mortality to forecast forest carbon stocks in British Columbia under environmental change scenarios
Project Description - Purpose, approach and duration:
This two-year project sought to develop a better understanding of environmental impacts on forest growth and mortality in British Columbia. The approach was to compile observations of growth, mortality, and net biomass production from permanent sample plots from across coastal Alaska, British Columbia, the Pacific Northwest U.S., and Alberta, thus allowing analysis over a wide range of climate and across species ranges. The data were used to build a better understanding of the processes that control growth and mortality and thus allowing us to better study how ongoing environmental change will affect the sustainability of timber supply and forest carbon balance.
Those Involved - Principle Investigator(s), HQP (graduate students and post-docs), partnering organizations:
This research was undertaken by:
Robbie A, Hember, Postdoctoral Fellow, U. British Columbia, visiting scientist at Pacific Forestry Centre, Natural Resources Canada;
Nicholas C. Coops, Professor, U. British Columbia;
Werner A. Kurz, Senior Research Scientist, Pacific Forestry Centre, Natural Resources Canada
Research Results
Observing trends in forest productivity in BC:
Prior to 2000, the BC inventory exhibits evidence of increasing forest growth that is consistent with predictions of some process-based models. Drought-induced mortality also increased strongly reducing net production in the Boreal Plains and Montane Cordillera ecozones. Observations of catastrophic drought-induced tree mortality did not appear to be associated with Mountain Pine Beetle, while efforts to acquire other insect activity databases was unsuccessful. With cooperation from the BC Ministry of Forests, Lands, and Natural Resource Operations, efforts to update the inventory for 2000-present were successful but only for plots on public lands. Despite evidence of catastrophic and increasing levels of drought-induced tree mortality in the Montane Cordillera and Boreal Plains ecozones, the monitoring programme post-2000 is inadequate for monitoring environmental impacts.
Empirical modelling:
A primary application of the inventory observations is the development of regression models that predict forest growth, which provide a much-needed alternative to process-based modelling. We developed such models for five North American ecozones, including the western temperate, Montane Cordillera, and boreal plain regions of British Columbia. The regression models demonstrate a remarkably consistent and physically-meaningful depiction of sensitivity: Growth declines with stand age, tree size, days with freezing, and evaporative demand and it increases with temperature, soil water content and atmospheric carbon dioxide.
Process-based modelling:
Inventory observations clearly demonstrate intra-specific variation in the environmental sensitivity of growth within species, but there is uncertainty in how much of it represents hydraulic adjustment (i.e., down-regulation of leaf area) or genetic trade-offs between hydraulic efficiency and vulnerability to embolism. In the interim, we are forced to make assumptions and map hydraulic traits using a climatological approach. Models were developed specifically to predict the effects of drought on probability of tree mortality. For the first time, we show conclusively that that drought is a primary driver of tree mortality, that actual evapotranspiration (not precipitation or potential evapotranspiration) is the primary instigating factor, and that the risk of this hydraulic failure increases with tree size in accordance with theoretical models.
Publications/Key Presentations - Where possible provide URLs:
Hember, R.A., Kurz, W.A., Coops, N.C., Metsaranta, J., in prep. Modelling water stress-induced tree mortality based on actual evapotranspiration, climatic water deficit, and tree size.
Hember, R.A., Kurz, W.A., Metsaranta, J., submitted. Moving beyond ring width: Why dendroecological studies should focus on absolute growth rate of trees. Trends in Plant Science (submitted).
Hember, R.A., Kurz, W.A., Coops, N.C., 2013. Representing cold tolerance in models of tree growth. Forest Genetics 2013, Whistler, BC. Oral presentaiton.
Wu, C., Hember, R.A., Chen, J.M., Kurz, W.A., Price, D.T., Boisvenue, C., Gonsamo, A., Ju, W., 2014. Accelerating Forest Growth Enhancement due to Climate and Atmospheric Changes in British Colombia, Canada over 1956-2001. Sci. Rep. 4. doi:10.1038/srep04461
Peng, Y., Arora, V. K., Kurz, W. A., Hember, R. A., Hawkins, B. J., Fyfe, J. C., and Werner, A. T.: Climate and atmospheric drivers of historical terrestrial carbon uptake in the province of British Columbia, Canada, Biogeosciences, 11, 635-649, doi:10.5194/bg-11-635-2014, 2014.
Outcomes: How is this research being used and by whom - Highlight the practical solution contribution of your research and policyrelevant outcomes, if applicable:
A map of monthly incident solar radiation was developed at 1 km spanning North America, while a second map at 100 m was developed for British Columbia. The maps provide the ability to estimate potential evapotranspiration and soil water content, which are key factors controlling forest biomass dynamics in BC ecosystems. The dataset is being used by numerous researchers external to the project and has been integrated into the ClimateWNA product. The 100 m version for BC will be used to drive models in BC.
Two process-based modelling groups have used the inventory-based estimates for comparison or calibration and published the results.
Project results inform on future development options for CMB-CFS. Pressure to account for environmental sensitivity of biomass dynamics in CBM-CFS and national greenhouse gas accounting is predominantly based on evidence from process-based modelling studies. This project presents evidence to suggest that state-of-the-art process models can reproduce general trends expressed by inventories, which is encouraging. However, the inventory also clearly demonstrates shortcomings in the way water stress is represented in process-based models. Namely, the inventory demonstrates that meteoric drought is predominantly controlled by available energy rather than saturation deficit and that biomass dynamics are strongly influenced by drought-induced tree mortality which is not currently represented by models.
Measuring Success - Did your research answer the question it set out to? Why/why not?
The project successfully expanded our understanding of the scope of the problem and successfully developed the most sophisticated permanent sample plot/climate database in the world to date. The project was unsuccessful in incorporating the models into CBM-CFS. This shortcoming was partially a reflection (1) intentionally emphasizing focus on the advancement of the growth and mortality models, themselves and (2) challenges in working with structural limitations of CBM-CFS3. This work is ongoing and revisions to the CBM-CFS3 are addressing the structural limitations. The development of environment-sensitive models of tree mortality is a major scientific advancement that will be adopted into precision forestry planning.