RESUMO
There is much uncertainty about how climate warming will impact greenhouse gases (GHG) budget in dry environments due to the lack of available data for desert biocrust soil. We implemented a 2.5-year field measurement of CO2, CH4 and N2O effluxes in cyanobacteria-dominated, moss-dominated and mixed (cyanobacteria, moss and lichen) biocrust soils using open-top-chambers to simulate climate warming (1.2 °C on average). Desert biocrust soils generally acted as a weak sink of atmospheric CH4 and N2O. Although warming effects on daily CO2, CH4, and N2O effluxes varied depending on sampling date and biocrust soil, there was no significant difference in daily, monthly and seasonal average CO2, CH4 and N2O effluxes between warming and control in most cases for three biocrust soils. However, warming caused a marginal (p = 0.06) decrease (14.2%) in annual accumulative CO2 efflux in moss-dominated biocrust soil due to the drought effects caused by warming indirectly and OTC sheltering of precipitation directly, while there was no significant difference between warming and control for cyanobacteria-dominated and mixed biocrust soils, implying a neutral response of GHG effluxes to climate warming. These results suggest that the GHG budget in arid desert biocrust soil would not be significantly changed in the warmer future when the direct negative effects of drought on CO2 effluxes were excluded. Therefore, a marginal decrease of accumulative CO2 effluxes in response to warming coupled with drought for moss-dominated biocrust soil might offer a weak negative feedback to warming and drier climate change pattern.
