Estimation of annual CO2 efflux of moss biocrust through measuring and simulating its respiration rate in a semiarid climate

[Display omitted] •Rs of biocrust was measured and modeled as a function of soil environment factors.•Variation of Rs in biocrust & bare soils was strongly predicted in regression models.•Rs averaged 1.03 and 0.54 μmol m−2 s−1 for biocrust and bare soil across all seasons.•Annual CO2-C efflux of biocrust and bare soil was 390 and 203 g m−2, respectively.•Contribution of biocrust to Rs may be linked to the C stored in the biocrust layer. Biocrust is a potentially extensive living cover in drylands, which comprises much of the land surface, but presently its contribution to the soil respiration rate (Rs) and CO2 efflux is still not clearly understood. In this study, we continuously measured the Rs of moss-dominated biocrust (biocrust and biocrust covered soil) and bare soil, together with soil temperature and moisture, for ~100 days each in a semiarid climate on the Chinese Loess Plateau. We modeled Rs across a two-year period, based on its relationship with soil temperature and moisture. Using the model, the seasonal variation of the Rs was simulated for biocrust and bare soil, and their annual CO2 efflux were further estimated. We also obtained samples of the biocrust layer and bare soil surface and analyzed their physicochemical properties and enzyme activities to explain the biocrust effects on Rs. Our results showed that the measured Rs of the biocrust and bare soil ranged from 0.05 to 7.62 and 0.02–2.73 μmol m−2 s−1, respectively, and was closely exponentially related to the dynamics of soil temperature and moisture (in threshold relationships). The variations of Rs in both the biocrust and bare soil were strongly predicted in a regression model by R2 ≥ 0.50 and P