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Research Project: Understanding Water-Driven Ecohydrologic and Erosion Processes in the Semiarid Southwest to Improve Watershed Management

Location: Southwest Watershed Research Center

Title: Ecological responses to heavy rainfall depend on seasonal timing and multi-year recurrence

item LI, L.F. - Chinese Academy Of Sciences
item ZHENG, Z.Z. - Chinese Academy Of Sciences
item Biederman, Joel
item XU, C. - Chinese Academy Of Sciences
item XU, Z.H. - Chinese Academy Of Sciences
item CHE, R.X. - Chinese Academy Of Sciences
item WANG, Y.F. - Chinese Academy Of Sciences
item CUI, X.Y. - Chinese Academy Of Sciences
item HAO, Y.B. - Chinese Academy Of Sciences

Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2019
Publication Date: 5/2/2019
Citation: Li, L., Zheng, Z., Biederman, J.A., Xu, C., Xu, Z., Che, R., Wang, Y., Cui, X., Hao, Y. 2019. Ecological responses to heavy rainfall depend on seasonal timing and multi-year recurrence. New Phytologist. 223:647-660.

Interpretive Summary: Heavy rainfall events are a climate change aspect that has already been observed and is expected to become more important in the future. We lack understanding about how heavy rainfall impacts agroecosystems. Here we conducted experiments using rainfall shelters and hand watering of a semiarid grassland to test the effects of a heavy rainfall event applied at different times of the growing season. Impacts were not immediately apparent, because above-ground plant productivity was not affected by the heavy rainfall. However, root production was inhibited by heavy rainfall when applied late in the growing season. These results suggest that if plants responds to heavy rainfall by reducing their root production, they may be more susceptible to future drought periods.

Technical Abstract: Heavy rainfall events are expected to increase in frequency and severity in the future. However, the effects of heavy rainfall on natural ecosystems are largely unknown, in particular with different event timing and recurrence. We conducted a four-year manipulative experiment to explore the response of grassland to heavy rainfall imposed in either mid- or late-growing season, respectively, in Inner Mongolia, China. We measured hierarchical responses at individual, community, and ecosystem levels. Surprisingly, aboveground productivity remained stable in the face of heavy rainfalls regardless of seasonal timing, while late-growing season heavy rainfall had consistent negative impacts on belowground and total productivity. However, such negative effects were not significant in heavy rainfall imposed in mid-growing season. By contrast, mid-growing season heavy rainfall had greater positive effects on ecosystem CO2 exchanges, mainly in the latter two years of the four-year experiment. Great stimulation of CO2 fluxes in latter two years by mid-growing season heavy rainfall was attributed to large community leaf area and high leaf photosynthesis of dominant species during treatment, reflecting plant physiological and morphological adaptation over years, as well as related to inter-annual variability in precipitation. Overall, our study demonstrates that ecosystem impacts of heavy rainfall crucially depend on the seasonal timing and recurrence. However, more carbon allocated to aboveground fraction rather that roots for coping with heavy rainfalls may decrease the stability of this ecosystem during subsequent climate change in this typically water-limited environment.