OOS 32-1 - How ecological stoichiometry can be applied as a tool to inform sustainable forest management.

Background/Question/Methods
Forest managers manage forests sustainably for different values, including biodiversity, wildlife habitat, hydrology, climate mitigation, recreation and commercial harvest. Quantifying these values can be challenging. Monetization of ecosystem services is one solution. Another is to use some of the basic currency for all organisms; carbon (C), nitrogen (N) and phosphorous (P). Ecological stoichiometry examines how intraspecific variation in the distribution of these elements affects a variety of ecological processes. Canada’s boreal forests are widely seen as carbon sinks, and their persistence is assumed to play an important role in climate change mitigation. However, carbon is one elemental trait, and we know there is inter- and intra-specific variation in stoichiometric traits across organisms. In our research group, we are interested in how C, N and P are stored in boreal plants and herbivores, and how these elements move through forest ecosystems in space, time and along food chains. We apply ecological stoichiometry to address how the distribution of C, N, and P in boreal forests is influenced by environmental heterogeneity, temporal forest dynamics, disturbance events (insects, fire), and herbivory. Our methods combine field data collection, spatial modelling and manipulative experiments in a boreal forest system on the island of Newfoundland, Canada.

Results/Conclusions
We sampled four boreal plants (balsam fir Abies balsmaea, white birch Betula papyrifera, red maple Acer rubrum, and blueberry Vaccinium angustifolium) across a forest stand chronosequence (20-40; 40-60; 60-80; 80+ years) and sent samples for C, N, and P analysis. We used these data in combination with readily available GIS and remotely sensed data to develop spatial stoichiometric distribution models for plant elemental quantity, percent, and ratios. We show that C, N and P in our focal boreal plants changes more in space than in time and identify environmental drivers for inter- and intra-specific variation in elemental composition. We also focused on a keystone herbivore that feeds on our focal plant species, the snowshoe hare (Lepus americanus). We examined whether elemental composition of hares varies by sex and age, and whether hares make foraging decisions based on variation in elemental composition of their browse. Finally, we examine how home range size of snowshoe hares may be affected by resource stoichiometry in the areas they use. Based on our findings, we illustrate how an ecological stoichiometry lens can help inform different facets of forest management, including carbon management, response to disturbances, and relationships between forest management strategies and wildlife.