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Abstract: Large herbivores can directly and indirectly alter carbon (C) cycling. In turn, predation can mediate the effects of large herbivores on plant growth and successional trajectories, thereby indirectly changing ecosystem C fluxes. It is, however, uncertain how these trophic cascades will affect biogeochemical cycles in a warming climate. In cold climates, warming is likely to increase both primary production and ecosystem respiration. These ecosystem dynamics are affected by browsing herbivores, which consume and thus suppress some tree species and avoid others, leading to indirect changes to productivity and detrital inputs to soil C pools. To evaluate the potential emergent outcomes of climate change, herbivores, and predator management on ecosystem C storage, we used a landscape simulation model to project changes in carbon cycling as a function of the interactions among forest succession, moose populations, and climate change at Isle Royle, MI, USA.
Under a warmer climate, we estimate large increases in productivity, respiration, and soil C storage, resulting in a net increase in ecosystem C storage of ~10-30 Mg ha-1 over 80 years. Compared to the effects of climate, there were modest contributions of predation to increased productivity, and minor changes to the adult tree community. Initially, scenarios with high predation stored 40 g C m-2 yr-1 more than those with very low predation, but this effect dwindled to an average of 11 g C m-2 yr-1 over the course of an 80-year simulation. The effect of predation was limited under the warmest climate change scenarios, where, regardless of predation, recruitment of palatable boreal species collapsed, and climatic influences became much more important than predation. Gains in aboveground biomass due to warming were driven by increased productivity of boreal conifers during longer growing seasons. In contrast, regeneration shifted almost entirely to temperate species. While moose have near-term impacts on carbon cycling and tree demography, climatic changes are likely to overwhelm those effects.
Funding: USGS
Collaborators: Samuel Flake, Robert Scheller, Nate De Jager
Status: Ongoing
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