Abstract
Grazing is an important modulator of both plant productivity and biodiversity in grassland community, yet how to determine a suitable grazing intensity in alpine grassland is still controversy. Here, we explore the effects of different grazing intensities on plant biomass and species composition, both at community level and functional group level, and examines the productivity–species richness relationship under four grazing patterns: no grazing (CK), light grazing (LG), moderate grazing, (MG) and heavy grazing (HG), attempt to determine a suitable grazing intensity in alpine grassland. The results were as follows. The total aboveground biomass (AGB) reduced with increasing grazing intensity, and the response of plant functional groups was different. AGB of both sedges and legumes increased from MG to HG, while the AGB of forbs reduced sharply and the grass AGB remained steady. There was a significant positive relationship between productivity and species richness both at community level and functional group level. In contrast, the belowground biomass (BGB) showed a unimodal relationship from CK to HG, peaking in MG (8,297.72 ± 621.29 g/m2). Interestingly, the grassland community tends to allocate more root biomass to the upper soil layer under increasing grazing intensities. Our results suggesting that moderate levels of disturbance may be the optimal grassland management strategy for alpine meadow in terms of root production.
Highlights
The impacts of grazing on soil condition have been well documented in previous studies, whereas no consensus has been obtained regarding the effect of grazing intensity on species composition and grassland productivity
Given the non‐normal data distributions of both aboveground biomass (AGB) and belowground biomass (BGB), the Wilcoxon rank test was used to compare the differences in biomass among the four grazing intensities, and a general linear model (GLM) was applied to examine the simple linear relationship between AGB and species richness across both the community and plant functional groups
Our results show that the AGB was reduced by increasing grazing intensity, but that individual plant functional groups showed varied responses to the different intensities of livestock grazing
Summary
Grassland is widely distributed around world, making a great contribution to the balance between forage productivity and livestock (Feng et al, 2010), and playing a vital role in the global carbon cycle (Yang, Fang, Ji, & Han, 2009). It has been reported that the grazing can exert a negative effect on belowground biomass (Beaulieu, Gauthier, & Rochefort, 1996), yet there are many studies indicating that the belowground biomass is equal in grazed areas compared with ungrazed areas (Derner, Boutton, & Briske, 2006; Garcia‐Pausas, Casals, Romanyà, Vallecillo, & Sebastià, 2011). To addresses these uncertainties and determine a suitable grazing intensity in alpine grassland, it is necessary to assess the effects of different grazing intensities on grassland ecosystems. The main objectives of this study were to (a) explore the effects of different grazing intensities on community biomass both aboveground and belowground, (b) observe the vertical distribution of root biomass under different grazing intensities, and (c) examine the relationship between productivity and species richness
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