Does Grazing Matter for Soil Organic Carbon Sequestration in the Western North American Great Plains?
Does Grazing Matter for Soil Organic Carbon Sequestration in the Western North American Great Plains?
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DOI：
10.1007/s10021-018-0324-3
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发表时间：
2018-12
期刊：
影响因子：
3.7
通讯作者：
J. Derner;D. Augustine;D. Frank
中科院分区：
文献类型：
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作者：
J. Derner;D. Augustine;D. Frank
放牧对半干旱草原生态系统土壤有机碳(SOC)固存的影响仍然存在相当大的不确定性，这是因为与研究此类影响相关的三个重要困难：(1)由于放牧导致的SOC池相对于固有的大草原SOC池很难检测到具有生态意义的变化，(2)缺乏基线(处理前)数据，以及(3)长期放牧操作经常缺乏或复制有限。在科罗拉多州东北部的北美西部短草草原上，通过土壤质地梯度建立的74年放牧封禁地和中等放牧地对，确定了SOC固存速率。我们从12个封育场和放牧地对土壤(0-20厘米)进行采样，以测量土壤有机碳浓度和土壤放射性碳∆14C(‰)；后者使我们能够确定有无放牧的土壤有机碳在70年期间的周转。70年以上的放牧显著改变了植物群落的组成，但不影响土壤总碳、有机碳、土壤∆14C、有机碳周转速率或土壤总氮，放牧效应也没有与土壤质地相互作用来影响任何土壤性质。土壤质地(粉质 + 粘粒含量)对土壤全碳和全氮有影响，但对土壤∆14C和有机碳周转没有影响。结果表明，北美大平原西部半干旱草原生态系统长期放牧并不能加强长期的SOC固存，尽管C3和C4草的相对优势发生了变化。
Considerable uncertainty remains regarding grazing-induced influences on soil organic carbon (SOC) sequestration in semiarid grassland ecosystems due to three important complications associated with studying such effects: (1) Ecologically meaningful shifts in SOC pools attributable to grazing are difficult to detect relative to inherently large grassland SOC pools, (2) a lack of baseline (pre-treatment) data, and (3) frequent lack of or limited replication of long-term grazing manipulations. SOC sequestration rates were determined in 74-year-old grazing exclosures and paired moderately grazed sites, established across a soil texture gradient, in the western North American shortgrass steppe in northeastern Colorado. We sampled soils (0–20 cm) from 12 exclosures and paired grazed sites to measure SOC concentration and soil radiocarbon ∆14C (‰); the latter allowed us to determine turnover of the SOC pool over a 7-decade period in the presence versus the absence of grazing. Removal of grazing for more than 7 decades substantially altered plant community composition but did not affect total soil C, SOC, soil ∆14C, SOC turnover rate, or total soil N. Grazing effect also did not interact with soil texture to influence any of those soil properties. Soil texture (silt + clay content) did influence total soil C and SOC, and total soil N, but not ∆14C or SOC turnover. Results provide evidence that long-term removal of grazing from semiarid grassland ecosystems in the western North American Great Plains does not enhance long-term SOC sequestration, despite changes in the relative dominance of C3 versus C4 grasses.