Abstract：
Soils in semiarid riparian ecosystems have large carbon (C) stocks that promote water and nutrient availability for productive plant communities consumed by grazing animals. Changes to riparian hydrologic conditions caused by channel incision result in different edaphic conditions and a greater abundance of upland plant species that may be associated with lower soil C stocks. Using riparian meadows alongside Maggie Creek in central Nevada, we show that 27 years of modified grazing practices can repair ecosystem processes and increase the C stocks. We compared C and nitrogen (N) stocks (of soils and plant biomass) on floodplains, terraces, and uplands of reaches where grazing was either modified or excluded to reaches where no changes to grazing practices were made. Grazing management allowed beaver to establish, improving hydrology and lengthening the growing season. These changes allowed C and N to accumulate on geomorphic surfaces that extended from the stream channel to the surrounding hillslopes. A stoichiometric relationship between C and N shows carbon sequestration can reduce nutrient runoff to nearby waterways and may depend on nitrogen availability. Gains in ecosystem carbon ranged from 93 to 452 g C m-2 y-1 and were dominated by increases in soil C. Gains in soil C occurred across the full depth range measured (0-45 cm) and were comparable to those found in restored wetlands and meadows located in more humid ecosystems. Carbon gains exhibited substantial variability caused by microtopography and plant community composition. While grazing exclusion resulted in the largest gains in ecosystem C, managed grazing that limited consumption of riparian plants increased ecosystem C relative to reaches where management wasn\'t changed. We demonstrate that managed grazing that maintains ecosystem process is compatible with projects aimed at increasing soil carbon in semiarid riparian rangelands.
摘要：
半干旱河岸生态系统中的土壤具有大量的碳（C）储量，可促进放牧动物消耗的生产性植物群落的水和养分供应。由河道切口引起的河岸水文条件的变化导致不同的土壤条件和更多的旱地植物物种，这可能与较低的土壤碳储量有关。在内华达州中部的MaggieCreek旁边使用河岸草地，我们表明，经过27年的改良放牧实践可以修复生态系统过程并增加C库存。我们比较了洪泛区的碳和氮（N）储量（土壤和植物生物量），梯田,以及放牧被修改或排除在未改变放牧方式的区域的高地。放牧管理允许海狸建立，改善水文和延长生长季节。这些变化使C和N积累在从河道延伸到周围山坡的地貌表面上。C和N之间的化学计量关系表明，固碳可以减少养分径流到附近水道，并且可能取决于氮的利用率。生态系统碳的增长范围为93至452gCm-2y-1，主要是土壤C的增加。土壤C的增长发生在测量的整个深度范围（0-45cm）中，与在较潮湿的生态系统中恢复的湿地和草甸中发现的增长相当。碳增加表现出由微地形和植物群落组成引起的实质性变化。虽然放牧排斥导致了生态系统C的最大收益，相对于管理没有改变的地区，有限的河岸植物消费的管理放牧增加了生态系统C。我们证明，维持生态系统过程的有管理的放牧与旨在增加半干旱河岸牧场土壤碳的项目兼容。
