Abstract
AbstractNearly 90% of the 390 million ha of grasslands in northern China are degraded. ‘Grazing exclusion’ has been implemented as a nature‐based solution to rejuvenate degraded grasslands, but the effectiveness of the rejuvenation processes is uncertain. Here, we investigated the effects of grazing exclusion on aboveground plant community traits, soil physiochemical and biological properties, and the mechanisms responsible for enhanced grassland rejuvenation. A meta‐analysis across various studies was used to assess the effectiveness. On average, grazing exclusion improved vegetation coverage by 18.5 percentage points and increased aboveground biomass by 1.13 t ha−1 and root biomass by 1.27 t ha−1, which represent an increase of 84%, 246%, and 31%, respectively, compared with continuous grazing practices. Grazing exclusion reduced soil bulk density by 13.7% and increased soil water content by 68.9%. Grasslands under grazing exclusion increased soil organic carbon (SOC) in the 0‐ to 15‐cm depth by 3.95 (±0.35 Std err) t ha−1 and total soil N, available N, and total soil P in the 0‐ to 40‐cm depth by 2.39 (±0.14), 0.83 (±0.37), and 1.96 (±0.44) t ha−1, respectively, compared with continuous grazing; these values represent an increase of 31%, 25%, 23%, and 14%, respectively. Prolonging the duration (years) of grazing practices enlarged the differences in SOC and soil N content between grazing exclusion and continuous grazing. Grazing exclusion has improved plant community traits and enhanced soil physiochemical and biological properties of degraded grasslands, and thus, this ‘nature‐based’ approach can serve as an effective means to rejuvenate degraded grasslands.
Highlights
BACKGROUND OF NORTHERN CHINA GRASSLANDSAbout 40% of Chinese natural grasslands are concentrated in the temperate arid to semiarid northern part of the country
We summarize the major research findings on the effects of grazing intensity and the duration of grazing exclusion on plant community composition and diversity, vegetation characteristics, and soil physiochemical dynamics
Diversity heterogeneity can be related to the distribution of grazing animals (Ruifrok, Postma, Olff, & Smit, 2014), the different groups of plant species (Qu et al, 2016), and the critical threshold of N‐induced vegetation recovery capacity (Tang, Deng, An, Our meta‐analysis revealed significant effects of grazing practices on soil physiochemical properties (Table 2), and the magnitude of the effects varied between variables (Table 3)
Summary
Grasslands, one of the largest terrestrial ecosystems in the world, are crucial for wildlife habitat (Galli et al, 2012), livestock forage (Odriozola, García‐Baquero, Laskurain, & Aldezabal, 2014), and the livelihoods of nearly 800 million people globally (FAOSTAT, 2015). We summarized key results of 12 other published meta‐analyses, including the study on the effects of grazing exclusion on carbon sequestration from 78 studies (Xiong, Shi, Zhang, & Zou, 2016), biomass from 48 studies (Yan, Zhou, & Zhang, 2013), soil microbial communities from 71 studies (Zhao et al, 2017), carbon (C) and nitrogen (N) cycling from 115 studies (Zhou et al, 2017), and grassland management and greenhouse gas (GHG) emissions from 67 studies (Nayak et al, 2015). We cited key results from numerous articles that were not included in the meta‐analysis
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