Research Article: Effects of grazing patterns on grassland biomass and soil environments in China: A meta-analysis

Date Published: April 22, 2019

Publisher: Public Library of Science

Author(s): Yunqing Hao, Zhengwei He, Rafiq Islam.

http://doi.org/10.1371/journal.pone.0215223

Abstract

Grazing has important influences on the structures and functions of grassland ecosystems, but the effects of grazing patterns on grassland biomass and soil environments in China remain unclear.

We employed a meta-analysis to identify the response of biomass and soil environments to different grazing patterns in China.

Peer-reviewed journal articles were searched using the Web of Science and China National Knowledge to compile a database. A total of 1011 sets of sample observations satisfied the sampling standards; these were derived from 140 study sites and were obtained from 86 published articles. We conducted random effects meta-analyses and calculated correlation coefficients with corresponding 95% confidence intervals.

Grazing significantly decreased the total biomass, aboveground biomass (AGB), belowground biomass (BGB), soil organic matter, soil total nitrogen, soil total phosphorus and soil water content but increased the root-to-shoot ratio, soil available nitrogen, soil pH and bulk density. Generally, increasing grazing intensity and duration significantly increased the effects of grazing on the biomass and soil environment. Additionally, the smallest effects of grazing on the biomass and soil environments were observed under light grazing and cattle grazing alone. Moreover, non-growing season grazing significantly increased AGB, while annual grazing and growing-season grazing significantly reduced AGB. Furthermore, AGB was positively correlated with soil organic matter, soil available phosphorus and bulk density, while BGB was negatively correlated with pH.

These findings highlight the importance of grazing patterns in the biomass and soil environment response to grazing and suggest that cattle grazing alone and grazing during the non-growing season are beneficial for improving the quality of grassland in China.

Partial Text

Grasslands cover 3.55 × 108 hm2 in China, accounting for 6% ~ 8% of the world’s grassland area [1]. These areas are important for ecological services [2], such as carbon sequestration, water conservation, and livestock production [3–5]. At present, approximately all grasslands in China are used for grazing and are severely degraded [6]. Grazing is the most important method of grassland utilization and has an important influence on the structures and functions of grassland ecosystems [7, 8]. Grazing can contribute to compensatory growth in grasses. However, overgrazing may result in obvious changes in the composition and structure of the plant community and may lead to a significant decrease in the regenerative ability of grasslands, biomass, and the amount of nutrients returned to the soil through litter, eventually leading to grassland degradation [9].

In summary, this study employed a meta-analysis to identify the response of biomass and soil environments to different grazing patterns in China. In general, grazing significantly decreased the total biomass, AGB, BGB, soil organic matter, soil total nitrogen, soil total phosphorus and soil water content but clearly increased the root-to-shoot ratio, soil effective nitrogen, soil pH and bulk density. Generally, increasing the grazing intensity and duration significantly increased the effects of grazing on the biomass and soil environment. Additionally, the smallest effects of grazing on the biomass and soil environment were observed under light grazing and cattle grazing alone compared with sheep grazing alone and mixed grazing. Furthermore, in the non-growing season, grazing significantly increased AGB, while annual grazing and growing-season grazing significantly reduced AGB. The results also showed that AGB was positively correlated with soil organic matter, soil available phosphorus and soil bulk density, while BGB was negatively correlated with soil pH. Therefore, different grazing patterns regulate the response of the grassland biomass and soil environment to grazing.

 

Source:

http://doi.org/10.1371/journal.pone.0215223

 

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