Linkages — an individual-based forest ecosystem model

Carbon storage and flow through forest ecosystems are major components of the global carbon cycle. The cycle of carbon is intimately coupled with the cycle of nitrogen and the flow of water through forests. The supply of water for tree growth is determined by climate and soil physical properties. The rate at which nitrogen mineralization occurs depends on climate and the type of carbon compounds with which the nitrogen is associated. Species composition, which is also affected by climate, can greatly influence the composition of carbon compounds and subsequently nitrogen availability. Climate change can therefore have a direct effect on forest ecosystem production and carbon storage through temperature and water limitations, and an indirect effect through the nitrogen cycle by affecting species composition. Model simulations of these interactions show that climate change initiates a complex set of direct and indirect responses that are sensitive to the exact nature of the project climate changes. We show results using four different climate-change projections for a location in northeastern Minnesota. Modeled forest responses to each of these climate projections is different indicating that uncertainties in the climate projections may be amplified further as a result of shifts in balance between positive and negative ecosystem feedbacks.