Effects of grazing intensity on soil labile organic carbon fractions in a desert steppe area in Inner Mongolia

Jixin Cao,Yun Tian,Xiaoping Wang,Lin Zhang,Xiangyang Sun

doi:10.1186/2193-1801-2-s1-s1

Abstract

Grazing can cause changes in soil carbon (C) level. This study aimed to elucidate the response of soil labile organic carbon (SLOC) under four different grazing intensities: non grazing (NG), 0 sheep·ha-1; light grazing (LG), 0.91 sheep·ha-1; moderate grazing (MG), 1.82 sheep·ha-1, and heavy grazing (HG), 2.73 sheep·ha-1. Results showed that there was no significant difference in total soil organic carbon (TOC) and soil inorganic carbon (SIC) content from three soil depths (0-15 cm, 15-30 cm, and 30-45 cm) under different grazing intensities. However, the SLOC including particulate organic carbon (POC), light fraction organic carbon (LFOC), and readily oxidizable carbon (ROC) content at a depth of 0-15 cm decreased with the increasing grazing intensity among LG, MG and HG. The SLOC content at depths of 15-30 cm under the NG and LG were significantly higher than that under the MG and the HG. The TOC and SLOC content decreased with increasing depths of soil horizons, but SIC content increased. The variation trend of the density of different soil carbon fractions and the ratio of individual SLOC fractions to TOC were similar to that of the soil carbon content of corresponding fractions. These results indicated that MG and HG treatments caused C loss at 0-30 cm; and SLOC was more sensitive than TOC in response to different grazing intensities.

Highlights

Grasslands of various types comprise approximately 29.4% of the global land [1]
The total soil organic carbon (TOC) and soil labile organic carbon (SLOC) content decreased with increasing depths of soil horizons, but soil inorganic carbon (SIC) content increased
The three SLOC fractions (POC, light fraction organic carbon (LFOC) and readily oxidizable carbon (ROC)) content at a depth of 0-15 cm decreased with increasing grazing intensity among light grazing (LG), moderate grazing (MG) and heavy grazing (HG)

Summary

Introduction

Soil contains about 90% of total grassland systems carbon (C) [2], which store up to 30% of the world’s belowground C [3]. As one of the most important approaches, could modify the soil C stock in the grassland ecosystem and potentially influence climate change [4,5,6,7]. The investigation of the herbivores impact on the regulation of soil C is important to understand grassland ecosystems and to evaluate the contribution of grasslands to global C fluxes [8]. There are controversial reports on the effect of grazing on soil organic C level. Some studies reported that grazing increased soil C levels [2,9,10].

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Conclusion