Morra Brian, Brisbin Hondo, Stringham Tamzen, Sullivan Benjamin W
Department of Natural Resources and Environmental Science, The University of Nevada, Reno, 1664 N. Virginia St., Reno, NV, 89557, USA.
Department of Agriculture, Veterinary, and Rangeland Sciences, The University of Nevada, Reno, 1664 N. Virginia St., Reno, NV, 89557, USA.
J Environ Manage. 2023 Jul 1;337:117724. doi: 10.1016/j.jenvman.2023.117724. Epub 2023 Mar 24.
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 y 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.
半干旱河岸生态系统中的土壤含有大量碳（C）储量，这些储量有助于为食草动物食用的高产植物群落提供水分和养分。河道下切导致河岸水文条件发生变化，进而产生不同的土壤条件，并使高地植物物种数量增加，而这些物种可能与较低的土壤碳储量有关。在内华达州中部的玛吉溪沿岸的河岸草甸进行研究，我们发现27年的改良放牧实践能够修复生态系统过程并增加碳储量。我们比较了放牧方式改变或被排除的河段的河漫滩、阶地和高地（土壤和植物生物量的）碳和氮（N）储量，与放牧方式未改变的河段进行对比。放牧管理使得海狸得以栖息，改善了水文状况并延长了生长季节。这些变化使得碳和氮在从河道延伸至周边山坡的地貌表面上得以积累。碳和氮之间的化学计量关系表明，碳固存可以减少养分向附近水道的流失，并且可能取决于氮的有效性。生态系统碳的增加量在93至452克碳/平方米·年之间，主要是土壤碳的增加。土壤碳的增加发生在测量的整个深度范围内（0 - 45厘米），与在更湿润生态系统中恢复的湿地和草甸中的增加量相当。碳增加量因微地形和植物群落组成而表现出显著差异。虽然禁牧导致生态系统碳增加最多，但相对于放牧管理未改变的河段，限制河岸植物消耗的适度放牧增加了生态系统碳。我们证明，维持生态系统过程的适度放牧与旨在增加半干旱河岸牧场土壤碳的项目是兼容的。
