Department of Biology, Syracuse University, Life Sciences Complex, 107 College Place, Syracuse, NY 13244, USA.
Ecol Lett. 2010 Aug 1;13(8):959-68. doi: 10.1111/j.1461-0248.2010.01486.x. Epub 2010 May 12.
Grazing occurs over a third of the earth's land surface and may potentially influence the storage of 10(9) Mg year(-1) of greenhouse gases as soil C. Displacement of native herbivores by high densities of livestock has often led to overgrazing and soil C loss. However, it remains unknown whether matching livestock densities to those of native herbivores can yield equivalent soil C sequestration. In the Trans-Himalayas we found that, despite comparable grazing intensities, watersheds converted to pastoralism had 49% lower soil C than watersheds which retain native herbivores. Experimental grazer-exclusion within each watershed type, show that this difference appears to be driven by indirect effects of livestock diet selection, leading to vegetation shifts that lower plant production and reduce likely soil C inputs from vegetation by c. 25 gC m(-2) year(-1). Our results suggest that while accounting for direct impacts (stocking density) is a major step, managing indirect impacts on vegetation composition are equally important in influencing soil C sequestration in grazing ecosystems.
放牧发生在地球表面的三分之一以上的土地上，可能潜在地影响到每年储存 10(9) Mg 的温室气体作为土壤碳。由于高密度的牲畜取代了本地食草动物，经常导致过度放牧和土壤碳损失。然而，仍然不清楚是否可以使牲畜密度与本地食草动物相匹配，从而实现等量的土壤碳固存。在喜马拉雅山脉，我们发现，尽管放牧强度相当，但是转化为畜牧业的流域的土壤碳比保留本地食草动物的流域低 49%。在每个流域类型内进行的实验性放牧排除表明，这种差异似乎是由牲畜饮食选择的间接影响驱动的，导致植被变化，降低植物生产力，并减少可能来自植被的土壤碳输入约 25 gC m(-2) year(-1)。我们的研究结果表明，虽然考虑直接影响（放养密度）是一个主要步骤，但管理对植被组成的间接影响对于影响放牧生态系统中的土壤碳固存同样重要。
