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Plant species impacts on carbon and nitrogen cycling in grassland ecosystems
Human impacts on ecosystems, including rising atmospheric CO2 concentrations and species invasions, are increasing and can significantly alter carbon (C) and nitrogen (N) cycling on global and local scales. These trends make an understanding of species impacts on C and N cycling critical in order to predict responses of ecosystems to these changes. First we examined how species driven changes in N cycling can drive species invasions, particularly Pinus strobus invasion (Ch. 2). We found that high N residence time was the key trait driving P. strobus invasion success. Next, we examined how plant species differentially impact ecosystem C budgets and potential plant C harvest for biofuels (Ch. 3). After five years, P. strobus had significantly more aboveground harvestable C compared to all other species. Species differed in total ecosystem C accumulation, but for some species plant C gains were paralleled by declines in soil C. Species differed in C allocation, which has implications for C sequestration and potential biofuel production, and demonstrates that plant species can impact the distribution and amount of C above and belowground. Fourth, we examined four mechanisms of plant species effects on N cycling and the functioning of the soil microbial community that controls N availability to plants (Ch. 4). We found that plant species do not cause feedbacks on the ecosystem N cycling rate. However, plant C inputs to the soil control microbial immobilization and thereby change N partitioning between the plant and microbial pools. Finally, we examined the interaction between plant productivity, soil fertility, and changes in plant C inputs to the soil on microbial activity and N cycling, and how this interaction may feedback on plant performance (Ch. 5). We found that plant productivity was N limited and that plant C inputs may alter mineral N production but that soil fertility constrains this effect. Our results suggest that plant driven feedbacks on productivity via plant C inputs may be dependant on the size of the SOM pool.
Laungani, Ramesh G, "Plant species impacts on carbon and nitrogen cycling in grassland ecosystems" (2010). ETD collection for University of Nebraska - Lincoln. AAI3412878.