Short-term grazing exclusion has no impact on soil properties and nutrients of degraded alpine grassland in Tibet, China

X Lu,X Wang,G Cheng,X Zhang,Y Yan,Y Chen,J Sun

doi:10.5194/se-6-1195-2015

Abstract

Abstract. Since the 1980s, alpine grasslands have been seriously degraded on the Tibetan Plateau. Grazing exclusion by fencing has been widely adopted to restore degraded grasslands. To clarify the effect of grazing exclusion on soil quality, we investigated soil properties and nutrients by comparing free-grazing (FG) and grazing exclusion (GE) grasslands in Tibet. Soil properties – including soil bulk density, pH, particle size distributions, and proportion of aggregates – showed no significant difference between FG and GE plots. Soil organic carbon, soil available nitrogen, and available phosphorus contents did not differ with grazing exclusion treatments in both the 0–15 and 15–30 cm layer. However, soil total nitrogen and total phosphorus contents were remarkably reduced due to grazing exclusion at 0–15 cm depth. Furthermore, growing season temperature and/or growing season precipitation had significant effects on almost all soil property and nutrient indicators. This study demonstrates that grazing exclusion had no impact on most soil properties and nutrients in Tibet. Additionally, the potential shift of climate conditions should be considered when recommending any policy designed for restoration of degraded soil in alpine grasslands in the future. Nevertheless, because the results of the present study come from a short-term (6–8 years) grazing exclusion, the assessments of the ecological effects of the grazing exclusion management strategy on soil quality of degraded alpine grasslands in Tibet still need long-term continued research.

Highlights

Soil is a key resource that contributes to the Earth system functioning as a control and manages the cycles of water, biota and geochemicals (Keesstra et al, 2012; ParrasAlcántara et al, 2013; Brevik et al, 2015)
The results from Analysis of covariance (ANCOVA) demonstrate that grazing exclusion, soil depth, and their interaction have no effect on most of soil properties; almost all soil property indicators were significantly impacted by climate factors, growing season temperature (GST) and/or growing season precipitation (GSP) (Table 2)
Climate conditions during the growing season played an important role in controlling the soil quality status of alpine grasslands in Tibet because GST and/or GSP were found to have significant effects on almost all soil property and nutrient indicators (Table 2)

Summary

Introduction

Soil is a key resource that contributes to the Earth system functioning as a control and manages the cycles of water, biota and geochemicals (Keesstra et al, 2012; ParrasAlcántara et al, 2013; Brevik et al, 2015). Unreasonable human management of the soil resources is resulting in land degradation due to soil erosion, soil organic matter exhaustion, loss of soil structure, pollution, forest fires or deforestation (Cerdà et al, 2009; Novara et al, 2011, 2013; GarcíaOrenes et al, 2012; Pereira et al, 2013; Zhao et al, 2013; Keesstra et al, 2014) This is why there is a need to restore and rehabilitate soils as a source of nutrients and services to humankind (Bai et al, 2013; Mekonnen et al, 2015a, b; Roa-Fuentes et al, 2015; Tejada and Benítez, 2014).

Methods

Results

Discussion

Conclusion