Grazing effects on soil characteristics and vegetation of grassland in northern China

Z Wang,Y Rong,D A Johnson,K Wang

doi:10.5194/se-7-55-2016

Abstract

Abstract. Large areas of grassland in the agro-pastoral region of northern China were converted into cropland for grain production, and the remaining grasslands are being overgrazed and seriously degraded. The objective of this study was to evaluate how reductions in grazing intensity affect the soil and vegetation characteristics in grasslands of northern China. Soil heterogeneity and vegetation characteristics were evaluated for ungrazed (UG), moderate grazing (MG), and heavy grazing (HG) sites. Grazing increased diversity, but heavy grazing decreased aboveground biomass and increased the non-grass component. The non-grass proportion of total biomass increased with grazing intensity, which was 8, 16 and 48 % for UG, MG and HG sites, respectively. Species richness at the MG and HG sites was significantly higher than at the UG site (P< 0.05) with 3.6, 5.5 and 5.7 for UG, MG and HG sites, respectively. Strong spatial dependence of the examined soil properties at 10 m scale for all grazed sites was revealed by the ratio of nugget to total variation (0–23 %). Overgrazing homogenized soil characteristics at a 10 m scale. The ranges of spatial autocorrelation for soil organic C (SOC) and total N were both > 120 m at the HG site, which was considerably larger than that at the MG and UG sites with corresponding distances of 17.3 and 20.8 m for the MG site and 8.6 and 15.0 m for the UG site, respectively. The sampling density and sampling space for the HG site could be decreased under this scale sampling interval (10 m). Therefore, MG was recommended as the preferred management alternative for grasslands in northern China because of increased plant diversity without negative consequences related to decreased forage quality, forage quantity and soil heterogeneity for the investigated soil properties in northern China's grasslands.

Highlights

Arid and semi-arid ecosystems are highly heterogeneous in space and time because of considerable variation in biotic and abiotic factors related to vegetation and soil properties (Schlesinger et al, 1996; Peters et al, 2006; García-Palacios et al, 2011)
Species richness at the 0.25 m2 scale was not significantly different (P < 0.05) between the moderate grazing (MG) (5.5) and heavy grazing (HG) site (5.7), which were significantly greater than the UG site (3.6) (Fig. 5a)
Our results showed that the ranges of spatial autocorrelation for Soil water content (SWC), soil organic C (SOC) and TN were smaller at the UG and MG sites than HG site

Summary

Introduction

Arid and semi-arid ecosystems are highly heterogeneous in space and time because of considerable variation in biotic and abiotic factors related to vegetation and soil properties (Schlesinger et al, 1996; Peters et al, 2006; García-Palacios et al, 2011). This heterogeneity is essential to provide multiple ecosystem functions and services such as biodiversity, habitats and ecosystem stability (Peters et al, 2006; Tongway and Ludwig, 2003; Wang and Shao, 2013). Overgrazing has profound effects on important ecosystem characteristics, such as water erosion (Cerdà and Lavee, 1999), soil water content (SWC) (Lin et al, 2010), soil organic carbon (SOC) (Su et al, 2006; Costa et al, 2015), total nitrogen (TN)

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Conclusion