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TECHNICAL REPORTS

Storage and Dynamics of Carbon and Nitrogen in Soil after Grazing Exclusion in Leymus chinensis Grasslands of Northern China

^a Key Lab. of Vegetation and Environmental Change, Inst. of Botany, Chinese Academy of Sciences, Beijing 100093, China
^b Inst. of Atmospheric Physics, Chinese Academy of Sciences, LAPC, Beijing 100029, China
^c Graduate Univ. of Chinese Academy of Sciences, Beijing 100049, China

^* Corresponding author (nphe{at}ibcas.ac.cn).

Received for publication April 19, 2007. Land-use change can lead to changes in soil carbon (C) and nitrogen (N) storage. This study aimed to determine the impact of long-term grazing exclusion (GE) on soil organic C and total N (TN) storage in the Leymus chinensis grasslands of northern China and to estimate the dynamics of recovery after GE. We investigated the aboveground biomass and soil organic C and TN storage in six contiguous plots along a GE chronosequence comprising free grazing, 3-yr GE, 8-yr GE, 20-yr GE, 24-yr GE, and 28-yr GE. Grazing exclusion for two decades increased the soil C and N storage by 35.7 and 14.6%, respectively, in the 0- to 40-cm soil layer. The aboveground net primary productivity and soil C and N storage were the highest with 24-yr GE and the lowest with free grazing. The storage increased logarithmically with the duration of GE; after an initial rapid increase after the introduction of GE, the storage attained equilibrium after 20 yr. A logarithmic regression analysis revealed 86.8 and 87.1% variation in the soil C storage and 74.2 and 80.7% variation in the soil N storage in the 0- to 10-cm and 0- to 40-cm soil layers, respectively. Based on these results, we suggest that two decades of GE would restore the L. chinensis grasslands from being lightly degraded to a stable productive condition with good soil C and N storage capacity. Our results demonstrated that by implementing GE, the temperate grasslands of northern China could facilitate significant C and N storage on decade scales in the context of mitigating global climate change.

Abbreviations: ANPP, aboveground net primary productivity • C, carbon • FG, free grazing • GE, grazing exclusion • GE3, 3-year grazing exclusion • GE8, 8-year grazing exclusion • GE20, 20-year grazing exclusion • GE24, 24-year grazing exclusion • GE28, 28-year grazing exclusion • N, nitrogen • SOC, soil organic carbon • SOM, soil organic matter