Predicting the effects of climate change on the structure and function of ecosystems is difficult because most ecosystems are staggeringly complex, with many directly and indirectly interacting animal and plant species. A recent study by Christenson and colleagues attempts to track the effects of climate change through a forest ecosystem in the northeastern US to understand how one climatic alteration might affect the plant community through multiple pathways.
The authors studied how changes in snow depth might affect the interaction between moose and some of the species they consume, namely balsam fir, sugar maple, and Viburnum. First, they found that decreasing the snow depth exposed plants to increased browsing by moose. Second, they found that decreasing snow depth caused the soil to freeze more readily, damaging plants at the roots as well. The combined damaging effects resulted in less nitrogen uptake, and excess nitrogen leaching from the soil. In the long run, soil nitrogen loss could negatively impact the plants, compromising their ability to survive. Interestingly, the three types of plants used in the study responded differently to the experimental treatments, with balsam fir faring much worse than Viburnum. Studies like this one provide valuable insights into the effects of climate change on ecosystem processes, but to fully understand how ecosystems will react requires experiments involving multiple climate change variables manipulated simultaneously, such as snow depth, temperature, and carbon dioxide.
Christenson, L., MJ Mitchell, PM Groffman, GM Lovett (2014). “Cascading effects of climate change on forest ecosystems: biogeochemical links between trees and moose in the northeast USA.” Ecosystems 17: 442-457.