Light grazing facilitates carbon accumulation in subsoil in Chinese grasslands: A meta‐analysis

• Published in: Global change biology Vol. 26; no. 12; pp. 7186 - 7197
• Main Authors: Jiang, Zhi‐Yun, Hu, Zhong‐Min, Lai, Derrick Y. F., Han, Dao‐Rui, Wang, Mei, Liu, Min, Zhang, Meng, Guo, Ming‐Yan
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.12.2020
• Subjects: aboveground biomass; Accumulation; Animals; belowground biomass; below‐ground biomass; Biomass; Carbon; Carbon - analysis; Carbon cycle; China; deeper soil; dynamics of soil carbon; Ecosystem; Ecosystem assessment; global change; Grassland; Grasslands; Grazing; grazing duration; Grazing intensity; Herbivory; Livestock; Meta-analysis; Soil; soil carbon; Soil depth; Soil dynamics; Soil layers; Soil surfaces; Soils; subsoil; Subsoils; China; below-ground biomass; dynamics of soil carbon; grasslands; grazing intensity; grazing duration; deeper soil
• ISSN: 1354-1013; 1365-2486; 1365-2486
• DOI: 10.1111/gcb.15326

Grazing by livestock greatly affects the soil carbon (C) cycle in grassland ecosystems. However, the effects of grazing at different intensities and durations on the dynamics of soil C in its subsoil layers are not clearly understood. Here, we compiled data from 78 sites (in total 122 published studies) to examine the effects of varying grazing intensities and durations on soil C content at different depths for grasslands in China. Our meta‐analysis revealed that grazing led to an overall decrease in soil C content and productivity of above‐ground vegetation (e.g., above‐ground biomass and litter) but an increase in below‐ground biomass. Specifically, the effects of grazing on soil C content became less negative or even positive with increasing soil depths. An increase of soil C content was consequently found under light grazing (LG), although soil C content still decreased under moderate and heavy grazing. The increase in soil C content under LG could be largely attributed to the increase of soil C content in subsoil layers (>20 cm), despite that soil C content in surface soil layer (0–20 cm) decreased. Moreover, the magnitude of increase in soil C content under LG in subsoil layers increased with grazing duration. A possible reason of the increase in soil C content in the subsoil layers was due to the increases in below‐ground biomass. Our study highlights that LG may modify the allocation of C input and promote its accumulation in subsoil layers, thus offsetting the negative impact of grazing on surface soil C content, a finding that has significant implications for C sequestration in grasslands. Light grazing (LG) increased the soil C content (SCC) owing to its positive effect on SCC in subsoil layers (>20 cm), although its effect in the surface soil layer (0–20 cm) was negative. A possible reason is that LG may promote the below‐ground biomass (BGB) in subsoil layers (>20 cm), offsetting the negative impact on above‐ground biomass (AGB) and litter. Blue downward pointing arrows represent decrease and red upward pointing arrows represent increase in the variables. SWC: soil water content.