Trampling Disturbance of Biocrust Enhances Soil Carbon Emission

Abstract

Biocrusts play an important role in the carbon cycle in arid and semiarid ecosystems. Activities such as livestock grazing can disturb ecosystem functions of biocrusts. However, it is unclear whether disturbance intensity impacts carbon emission from these biocrusts. Few studies have investigated the transformation of carbon within biocrusts after disturbance. Here, we conducted a field experiment on the Loess Plateau, China, in which we artificially simulated different intensities of trampling to examine the response of biocrust carbon emissions to disturbance. Our results demonstrate that disturbance significantly reduced biocrust coverage. The largest decreases were observed in the second through fourth intensity, which declined significantly by 12.6–17.1%. Disturbance decreased soil organic carbon content in the biocrust layer by 2.6 g kg−1–3.7 g kg−1 depending on the disturbance intensity. Disturbance significantly increased the soil easily oxidizable carbon (SEOC) content in the biocrust layer. The soil microbial biomass carbon (SMBC) content of the fifth intensity increased significantly by 70.3%. The soil mineralizable carbon (SMC) content of the fourth intensity increased significantly by 78.8%. Soil carbon emissions increased significantly with increasing disturbance intensity, were higher at night than during the day, and were higher in the summer than in the fall. Together, these findings indicate that the increase of carbon emission was mainly due to increases in SEOC and SMC. Trampling disturbance increases carbon emissions from biocrust soils. These losses of CO<inf>2</inf> from biocrust soils after disturbance may substantially reduce the biocrust contribution to the soil carbon budget. © 2020 The Society for Range Management