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Abstract: This paper will discuss TRIPLEX-Flux, a process-based model that estimates net ecosystem production (NEP) as well as analyzing the level of sensitivity of the model''s response by simulating CO2 flux in an existing old black spruce BOREAS site in central Canada. The research objectives were: (1) to test the TRIPLEX-Flux model simulations against flux tower measurements; and (2) to examine parameter and input variable effects on model response via sensitivity analysis. Validation of NEP data at 30min intervals derived from tower and chamber measurements showed that the NEP data from the model corresponded well with the measured NEP from the BOREAS site (R 2 >0.65). Sensitivity analysis demonstrated different levels of sensitivity between morning and noon periods and from the current to doubled atmospheric CO2 concentrations. Additionally, the comparison of different algorithms to calculate stomatal conductance showed that the NEP predicted by the model using the iteration algorithm was consistent with the results using a constant C i/C a of 0.74 for current and 0.81 for doubled CO2 concentrations. Varying parameter and input variable values by ±10% resulted in a similar model response between morning and noon periods (less than or equal to 27.6% and 27.4%, respectively). Most parameters were more sensitive at noon than they were in the morning except for those that were correlated with air temperature, suggesting that air temperature has considerable influence over model sensitivity for these parameters/variables. Air temperature effect was greater under doubled than it was under current atmospheric CO2 concentrations. In contrast, model sensitivity to CO2 decreased under doubled CO2 concentrations. [Copyright &y& Elsevier]

Abstract: The boreal forest, earth''s second largest terrestrial biome, is currently thought to be an important net carbon sink for the atmosphere. In this study, a newly developed carbon exchange model of TRIPLEX-Flux (with half-hourly time step) is used to simulate the ecosystem carbon exchange of a 75-year-old boreal mixedwood forest stand in northeast Ontario and a 110-year-old pure black spruce stand in southern Saskatchewan, Canada. Results of net ecosystem exchange (NEE) simulated by TRIPLEX-Flux for 2004 are compared with those measured by eddy-flux towers and suggest overall agreement between model simulation and observations. The mean coefficient of determination (R 2) is approximately 0.77 for boreal mixedwood and 0.62 for old black spruce. Differences between model simulation and observation may be attributed to uncertainties not only in model input parameters and calibration, but also in eddy-flux measurements caused by systematic and random errors. The model is able to capture the diurnal variations of NEE for the growing season (from May to August) of 2004 for both sites. Both boreal mixedwood and old black spruce were acting as carbon sinks for the atmosphere during the growing season of 2004. However, the boreal mixedwood stand shows higher ecosystem productivity, carbon sequestration, and carbon use efficiency than the old black spruce stand. [Copyright &y& Elsevier]

With 2% of the world’s forests and 17% of Canada’s forested land, Ontario plays a major role in maintaining Canada’s forests and managing them sustainably. Ontario is developing a set of criteria and indicators of sustainable forest management (SFM) to aid in conservation and sustainable management of its temperate and boreal (BO) forests. The criteria and indicators are intended to provide a framework for describing and assessing processes of SFM at a regional scale; and to improve the information available to the public and decision-makers. This paper describes three ecological indicators, evaluated using a carbon (C) budget model, a forest inventory database, and disturbance records to assess long-term sustainability of Ontario’s forest ecosystems based on the environmental conditions of the past 70 years. Results suggest that total net primary productivity (NPP) of Ontario’s forest ecosystems increased from 1925 to 1975 and then decreased between 1975 and 1990; Ontario’s forest ecosystems acted as a C sink between 1920 and 1980, and a C source from 1981 to 1990, mainly due to decreased average forest age and NPP caused by increased ecosystem disturbance (e.g. fire, insect and disease infestations, harvesting) since 1975. Current estimates from this analysis suggest that there is significant potential for Ontario’s forests to function as C sinks by reducing ecosystem disturbances and increasing growth and storage of C in the young forests throughout the province. [Copyright &y& Elsevier]

• First attempt to integrate both hydraulic failure and carbon starvation mechanisms into a process-based model for boreal forests. • The shape parameter for calculating percentage loss of conductivity is the most sensitive parameter to simulate tree mortality. • Water limitation is a key driver for drought-induced tree mortality in the western canadian boreal forests. Globally, increasing drought-induced tree mortality rates under climate change are projected to have far-reaching effects on forest ecosystems. Among these forest systems, the boreal forest is considered a 'tipping element' of the Earth's climate system. This forest biome plays a critical role in ecosystem services, structures and functions while being highly sensitive to drought stress. Although process-based models are important tools in ecological research, very few have yet been developed that integrate advanced physiological mechanisms to simulate drought-induced mortality in boreal forests. Accordingly, based on the process-based TRIPLEX model, this study introduces the new TRIPLEX-Mortality submodule for the Canadian boreal forests at the stand level, that for the first time successfully incorporates two advanced drought-induced physiological mortality mechanisms (i.e., hydraulic failure and carbon starvation). To calibrate and validate the model, 73 permanent sample plots (PSPs) were selected across Canada's boreal forests. Results confirm a good agreement between simulated mortality and mortality observations (R2 =0.79; P <0.01; IA=0.94), demonstrating good model performance in simulating drought-induced mortality in boreal forests. Sensitivity analysis indicated that parameter sensitivity increased as drought intensified, and the shape parameter (c) for calculating percentage loss of conductivity (PLC) was the most sensitive parameter (average SI = -3.51) to simulate tree mortality. Furthermore, the results of model input sensitivity analysis also showed that the model can capture changes in mortality under different drought scenarios. Consequently, our model is suitable for simulating drought-induced mortality in boreal forests while also providing new insight into improving model simulations for tree mortality and associated carbon dynamics in a progressively warmer and drier world. [ABSTRACT FROM AUTHOR]

The boreal forests, identified as a critical "tipping element" of the Earth's climate system, play a critical role in the global carbon budget. Recent findings have suggested that terrestrial carbon sinks in northern high-latitude regions are weakening, but there has been little observational evidence to support the idea of a reduction of carbon sinks in northern terrestrial ecosystems. Here, we estimated changes in the biomass carbon sink of natural stands throughout Canada's boreal forests using data from long-term forest permanent sampling plots. We found that in recent decades, the rate of biomass change decreased significantly in western Canada (Alberta, Saskatchewan, and Manitoba), but there was no significant trend for eastern Canada (Ontario and Quebec). Our results revealed that recent climate change, and especially drought-induced water stress, is the dominant cause of the observed reduction in the biomass carbon sink, suggesting that western Canada's boreal forests may become net carbon sources if the climate change-induced droughts continue to intensify.

Background: Cultural variations in the relative emphasis on somatic versus psychological symptoms of distress are a common topic in cultural psychopathology. The most well-known example involves people of Chinese heritage, who are found to emphasize somatic symptoms in presenting depression as compared with people of Western European heritage. It remains unknown whether a similar cultural difference is found for anxiety disorders., Methods: Euro-Canadian (n=79) and Han Chinese (n=154) psychiatric outpatients with clinically significant concerns about both depression and anxiety were selected from a larger dataset based on their responses to a structured interview. They also completed two self-report questionnaires assessing somatization of depression and anxiety., Results: As expected, Chinese participants reported a greater tendency to emphasize somatic symptoms of depression, as compared to the Euro-Canadians. Contrary to expectations, the tendency to emphasize somatic symptoms of anxiety was higher among the Euro-Canadians as compared to the Chinese participants., Limitations: Characteristics of our participants limit the generalizability of our findings. The current study is preliminary and requires replication., Conclusions: Despite the exploratory nature of this study, the results suggest that the popular notion of 'Chinese somatization' should not be over-generalized. Our findings also imply that there may be important differences in the cultural understanding of depression and anxiety in both Chinese and 'Western' contexts. Future studies should seek to unpack potential cultural explanations for why Euro-Canadian outpatients may emphasize somatic symptoms in the presentation of anxiety to a greater degree than Chinese outpatients., (Copyright © 2011 Elsevier B.V. All rights reserved.)