School of Agriculture, Ningxia University, Yinchuan, China.
State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China.
Sci Rep. 2019 Nov 6;9(1):16088. doi: 10.1038/s41598-019-52631-6.
Fencing for grazing exclusion has been widely found to have an impact on grassland soil organic carbon (SOC) and total nitrogen (TN), but little is known about the impact of fenced grassland on the changes in deep soil carbon (C) and nitrogen (N) stocks in temperate grasslands. We studied the influence of 30 years fencing on vegetation and deep soil characteristics (0-500 cm) in the semi-arid grasslands of northern China. The results showed that fencing significantly increased the aboveground biomass (AGB), litter biomass (LB), total biomass, vegetation coverage and height, and soil water content and the SOC and TN in the deep soil. The belowground biomass (BGB) did not significantly differ between the fenced and grazed grassland. However, fencing significantly decreased the root/shoot ratio, forbs biomass, pH, and soil bulk density. Meanwhile, fencing has significantly increased the C and N stocks in the AGB and LB but not in the BGB. After 30 years of fencing, the C and N stocks significantly increased in the 0-500 cm soil layer. The accumulation of SOC mainly occurred in the deep layers (30-180 cm), and the accumulation of TN occurred in the soil layers of 0 to 60 cm and 160 to 500 cm. Our results indicate that fencing is an effective way to improve deep soil C and N stocks in temperate grassland of northwest China. There were large C and N stocks in the soil layers of 100 to 500 cm in the fenced grasslands, and their dynamics should not be ignored.
围封放牧已被广泛发现对草原土壤有机碳（SOC）和总氮（TN）有影响，但对于围封草原对温带草原深层土壤碳（C）和氮（N）储量变化的影响知之甚少。我们研究了 30 年围封对中国北方半干旱草原植被和深层土壤特性（0-500cm）的影响。结果表明，围封显著增加了地上生物量（AGB）、凋落物生物量（LB）、总生物量、植被盖度和高度，以及土壤水分含量和深层土壤中的 SOC 和 TN。围封和放牧草地之间的地下生物量（BGB）没有显著差异。然而，围封显著降低了根/枝比、杂类草生物量、pH 值和土壤容重。同时，围封显著增加了 AGB 和 LB 的 C 和 N 储量，但 BGB 没有增加。经过 30 年的围封，0-500cm 土壤层中的 C 和 N 储量显著增加。SOC 的积累主要发生在深层（30-180cm），TN 的积累发生在 0-60cm 和 160-500cm 的土壤层中。我们的结果表明，围封是提高中国西北温带草原深层土壤 C 和 N 储量的有效方法。围封草地的 100-500cm 土壤层中存在大量的 C 和 N 储量，其动态不容忽视。
