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Temperature increasing and precipitation alteration are predicted to occur in arid and semiarid lands; however, the response mechanism of carbon and water exchange at community level is still unclear in semiarid sandy land. We investigated the responses of carbon and water exchanges to warming and precipitation enhancement along a sand dune restoration gradient: mobile sand dunes (MD), semifixed sand dunes (SFD), and fixed sand dunes (FD). The average net ecosystem productivity (NEP) and evapotranspiration (ET) between May and August increased by 98% and 59%, respectively, from MD to SFD, while they had no significant differences between FD and the other two habitats. Warming inhibited ecosystem NEP, ET, and water use efficiency (WUE) by 69%, 49% (p < .001), and 80%, respectively, in SFD, while it nearly had no significant effects in MD and FD. However, precipitation addition by 30% nearly had no significant effects on community NEP, ET, and WUE, except for warming treatment in FD. In general, precipitation addition of 30% may still not be enough to prevent drought stress for growth of plants, due to with low water holding capacity and high evaporation rates in sandy land. Temperature increase magnified drought stress as it increased evapotranspiration rates especially in summer. In addition, community NEP, ET, and WUE were usually influenced by interactions between habitats and temperature, as well as the interactions among habitats, temperature, and precipitation. Species differences in each habitat along the restoration gradient may alter climate sensitivity of sandy land. These results will support in understanding and the prediction of the impacts of warming and precipitation change in semiarid sandy grassland. [ABSTRACT FROM AUTHOR]

The frequency and amount of precipitation exert profound impacts on plants and the soil subsystem in dryland ecosystems. To quantitatively assess the effect of precipitation on ecosystem carbon fluxes during the growing season, a field experiment was carried out in a native desert‐grassland ecosystem in Inner Mongolia to determine the dynamics of ecosystem carbon fluxes along a precipitation gradient (−60%, −40%, −20%, CK, +20%, +40%, and +60%; CK is natural precipitation). The net ecosystem productivity (NEP) and gross ecosystem productivity (GEP) exhibited a single peak, whereas ecosystem respiration (Reco) exhibited a bimodal peak across all precipitation treatments. Reco reached its highest value at the beginning of August, whereas NEP and GEP reached their highest values at the end of August. Mean values of carbon fluxes increased with an increase in precipitation (from NEP: 0.06 μmol · m−2 · s−1, Reco: 0.37 μmol · m−2 · s−1, GEP: 0.42 μmol · m−2 · s−1 at −60% to NEP: 1.25 μmol · m−2 · s−1, Reco: 0.93 μmol · m−2 · s−1, and GEP: 2.18 μmol · m−2 · s−1 at +60%). Increased precipitation stimulated GEP more so than Reco during the growing season, resulting in an enhanced NEP, and decreased precipitation reduced GEP more so than Reco, leading to a reduced NEP. We concluded that the carbon sequestration capacity was enhanced by increased precipitation in the desert‐grassland ecosystem. Key Points: Ecosystem carbon flux increased with precipitation increaseCarbon sequestration capacity was enhanced by increased precipitation in the desert‐grassland ecosystem [ABSTRACT FROM AUTHOR]