Increasing precipitation promotes carbon exchange in the Stipa breviflora desert steppe ecosystem

Abstract

A five-year rainfall control experiment was conducted in-field on the Stipa breviflora desert steppe in Inner Mongolia, China. We set four precipitation gradients on the fenced grassland: reduce precipitation by 50%, P1; natural precipitation, P2; increase precipitation by 50%, P3; increase precipitation by 100%, P4. We used a portable photosynthesis system Li-6400 measured the ecosystem carbon and water fluxes of each plot during the growing season (May-October). Results showed that precipitation had a significant impact on ecosystem carbon exchange. With increasing precipitation, net ecosystem carbon exchange (NEE), ecosystem respiration (ER), gross ecosystem productivity (GEP), evapotranspiration (ET) and water use efficiency (WUE) increased by 1.89, 0.37, 2.21, 0.80 µmol·m-2·s-1 and 2.16 µmol·mmol-1, respectively. NEE、ER、GEP、WUE is more sensitive to precipitation. Increasing precipitation will significantly increase the aboveground biomass of C3 species and promote carbon flux. In summary, increasing precipitation will increase carbon flux and promote carbon sink on the desert steppe.