The Catalysis of Belowground Processes in Grazing Ecosystems

社会面临的一个主要挑战是了解导致大气二氧化碳浓度的生态过程以及人类土地利用做法如何影响大气二氧化碳水平。已知食草动物强烈影响植物和土壤碳动态；但食草动物是如何决定碳流入和流出土壤的速度的，目前还不清楚。在这项研究中，麋鹿和野牛放牧对黄石国家公园碳过程的影响将在三个生态重要的时间尺度上进行研究：(1)生态系统二氧化碳交换的瞬时速率，(2)碳被植物吸收后1-3年的植物-土壤系统碳流速率，以及(3)40-50年的土壤碳储量。黄石公园是一个曾经广泛而稳定的草原生态系统仅存的少数遗迹之一，该生态系统在史前时期支持了大量的迁徙有蹄类动物，因此可以作为比较放牧草地的自然基准。由于地球一半的陆地面积被用作大型食草动物的牧场，有蹄类动物对全球碳循环的影响可能是巨大的。这项研究将有助于我们对放牧草地碳动态调控因素的理解。

A major challenge facing society is understanding the ecological processes contributing to atmospheric CO2 concentrations and how human land use practices influence atmospheric CO2 levels. Herbivores are known to strongly affect plant and soil carbon dynamics; but how grazers may determine the rate that carbon flows into and out of the soil remains unclear. In this study, the effects of grazing by elk and bison on carbon processes in Yellowstone National Park will be examined at three ecologically important time scales: (1) instantaneous rates of ecosystem CO2 exchange, (2) the rate that carbon flows through the plant - soil system during yrs 1-3 after carbon is assimilated by plants, and (3) 40-50 yr soil carbon storage. Yellowstone Park is one of the few remaining vestiges of a once widespread and stable grassland ecosystem that supported abundant migratory ungulates in prehistory, and thus can serve as a natural benchmark against which to compare grassland managed for livestock. With half of the earth's terrestrial surface area used as rangeland for large herbivores, the impact of ungulates on the global carbon cycle may be substantial. This research will contribute significantly to our understanding of factors that regulate carbon dynamics in grazed grassland.