Experimental climate change in desert steppe reveals the importance of C4 plants for ecosystem carbon exchange

Abstract

Global climate change has greatly altered plant community composition and affected ecosystem carbon exchange of grasslands. However, the influences of long-term increasing temperature and precipitation on the composition of plant community and the ecosystem carbon exchange in degraded desert steppe remain unclear. After seven years of simulated climate warming (ambient temperature, W0, 2 ℃ and 4 ℃ increase in temperature, W1 and W2) and increasing precipitation (plant growing season precipitation, P0, 25% and 50% increase in precipitation, P1 and P2), we recorded the composition of plant community, the moisture and temperature of soil and calculated net ecosystem CO2 exchange (NEE). Results showed that 1) long-term warming and increasing precipitation improved the cover and height of C4 plants in the plant community, while decreasing the cover and density of C3 plants. 2) Climate warming and increasing precipitation significantly increased NEE. Compared with W0P0, the mean NEE in the plant growing season increased by 115% in W2P2. 3) Redundancy analysis showed that soil moisture content and the height and density of C4 plants significantly explained ecosystem carbon exchange (P < 0.01), while the effect of C3 plants on ecosystem carbon exchange was insignificant (P > 0.01). Therefore, our research revealed that warming and increasing precipitation positively affected ecosystem carbon exchange in degraded desert steppe through changes in plant community composition, and C4 plants will play a vital role in ecosystem carbon exchange in desert steppe under climate change.