A six-year grazing exclusion changed plant species diversity of a Stipa breviflora desert steppe community, northern China.

Xing Wang,Yi Xue,Lin Chen,Lei Wang,Xinguo Yang,Junlong Gu,Naiping Song

doi:10.7717/peerj.4359

Abstract

Excluding grazers is one of most efficient ways to restore degraded grasslands in desert-steppe communities, but may negatively affect the recovery of plant species diversity. However, diversity differences between grazed and fenced grasslands in desert-steppe are poorly known. In a Stipa breviflora desert steppe community in Northern China, we established six plots to examine spatial patterns of plant species diversity under grazed and fenced conditions, respectively. We addressed three aspects of species diversity: (1) The logistic, exponential and power models were used to describe the species-area curve (SAR). Species richness, abundance and Shannon diversity values change differently with increasing sampling areas inside and outside of the fence. The best fitted model for SAR was the logistic model. Excluding grazers had a significant impact on the shape of SAR. (2) Variograms was applied to examine the spatial characteristics of plant species diversity. We found strong spatial autocorrelations in the diversity variables both inside and outside the fence. After grazing exclusion, the spatial heterogeneity decreased in species richness, increased in abundance and did not change in Shannon diversity. (3) We used variance partitioning to determine the relative contributions of spatial and environmental factors to plant species diversity patterns. Environmental factors explained the largest proportion of variation in species diversity, while spatial factors contributed little. Our results suggest that grazing enclosures decreased species diversity patterns and the spatial pattern of the S. breviflora desert steppe community was predictable.

Highlights

Human disturbance and global climate change pose severe threats to biodiversity and ecosystem functioning of grasslands (Bai et al, 2012; Shao et al, 2016)
Grazing exclusion had a significant effect on the parameters of the species–area curve (SAR) models
Species–area curves as the first pattern at the community level was better fitted by the logistic model rather than the power function

Summary

Introduction

Human disturbance and global climate change pose severe threats to biodiversity and ecosystem functioning of grasslands (Bai et al, 2012; Shao et al, 2016). The dramatic degradation of grasslands has prompted efforts to restore them through ecological methods such as planting shrubs, excluding grazers, introducing species and changing land use. How to cite this article Wang et al (2018), A six-year grazing exclusion changed plant species diversity of a Stipa breviflora desert steppe community, northern China. Grazing enclosures can have negative effects on plant species diversity due to litter accumulation, altered competition for water and light, and competitive exclusion of species (Guo, 2005; Wu & Thirgood, 2009; Jing, Cheng & Chen, 2013). Understanding which mechanisms underlie the change in species diversity due to grazing exclusion is critical to an informed management of restoration efforts in steppe-grasslands

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