Zhang Yi, Xie Yingzhong, Ma Hongbin, Jing Le, Matthew Cory, Li Jianping
School of Agriculture, Ningxia University, Yinchuan, Ningxia, China.
School of Agriculture and Environment, Massey University, Palmston North, NewZealand.
PeerJ. 2020 May 5;8:e8986. doi: 10.7717/peerj.8986. eCollection 2020.
Our study evaluated how soil organic carbon (SOC) and soil inorganic carbon (SIC) recovered over time in deep loessial soil as overgrazed grassland was fenced and restored.
The study was conducted in the Yunwu Mountain Nature Reserve in the Ningxia Autonomous Region of China. In it we compared soil data from three grazed grassland (G) sites, three sites that were fenced for 15 years (F15), and three sites that were fenced for 30 years (F30) as a so-called 'space for time series'.
We compared SOC accumulation in soil up to 200 cm below the surface in G, F15, and F30 plots. An increase in SOC correlated with a decrease in soil pH, and decreased soil bulk density. However, SOC sequestration in fenced plots was largely offset by a decrease in SIC, which was closely correlated ( = 0.713, = 0.001) with SOC-driven soil pH decline. We observed no significant increase in soil total carbon in the F15 or F30 sites after comparing them to G.
Our data indicate that fencing causes the slow diffusion processes to intensify the soil property changes from increased litter return, and this slow diffusion process is still active 30 years after fencing at 100-200 cm soil depths in the studied deep loessial soil. These findings are likely applicable to similar sites.
我们的研究评估了在过度放牧的草地围栏封禁并恢复后，深层黄土土壤中的土壤有机碳（SOC）和土壤无机碳（SIC）如何随时间恢复。
该研究在中国宁夏回族自治区的云雾山自然保护区进行。我们将三个放牧草地（G）样地、三个围栏封禁15年的样地（F15）和三个围栏封禁30年的样地（F30）的土壤数据进行比较，以此作为所谓的“时间序列替代空间”。
我们比较了G、F15和F30样地中地表以下200厘米深度内土壤中SOC的积累情况。SOC的增加与土壤pH值的降低以及土壤容重的减小相关。然而，围栏封禁样地中SOC的固存很大程度上被SIC的减少所抵消，SIC的减少与SOC驱动的土壤pH值下降密切相关（r = 0.713，P = 0.001）。将F15和F30样地与G样地比较后，我们未观察到土壤总碳有显著增加。
我们的数据表明，围栏封禁导致缓慢扩散过程加剧了因凋落物归还增加而引起的土壤性质变化，并且在研究的深层黄土土壤中，这种缓慢扩散过程在围栏封禁30年后，在100 - 200厘米土壤深度处仍然活跃。这些发现可能适用于类似的地点。
