Divergent effects of biological soil crusts on soil respiration between bare patches and shrub patches under simulated rainfall in a desert ecosystem in Northwest China

Abstract

The important role of biological soil crusts (biocrusts) in determining the soil carbon balance in dryland ecosystems under future climate change has been widely explored. However, when assessing the effects of biocrusts on soil respiration, few studies have considered biocrusts in bare soil patches and shrub soil patches. A field experiment was performed with five simulated rainfall addition events (0, 5, 15, 25, and 40 mm) in shrub and bare soil patches in June (early growing season, EGS), July (middle growing season, MGS) and September (late growing season, LGS) in 2016 and 2017. Our objective was to examine whether biocrusts at shrub and bare soil patches have the same effect on soil respiration under altered rainfall regimes. The results showed that the removal of biocrusts from bare patches reduced soil respiration by 15 % after rainfall amounts of 5–40 mm and increased the subsurface soil temperature and decreased the soil moisture after various rainfall treatments. However, in shrub patches, the removal of biocrusts led to a significant increase in soil respiration of 57 % and subsequent increases in subsurface soil temperature and moisutre. The discrepancy in the soil respiration response between the two types of patches might be attributable to the increase in soil infiltration after biocrust removal, with a greater stimulating increase in soil carbon emissions stimulated in the shrub patches than in the bare patches due to more the greater amounts of roots distributed under the former shrub patches. Our results indicate that the destruction of biocrusts in shrub patches may reduce the ability of biocrust ecosystems to become a net carbon sinks, with potentially negative consequences for ecosystem function and sustainability in water-limited regions.