Drought timing influences the sensitivity of a semiarid grassland to drought

Authors: LI, L.F. - University Of Chinese Academy Of Sciences; QIAN, R. - University Of Chinese Academy Of Sciences; LIU, W. - University Of Chinese Academy Of Sciences; WANG, W. - University Of Queensland; Biederman, Joel; ZHANG, B. - University Of Chinese Academy Of Sciences; KANG, X.M. - Chinese Academy Of Forestry; WEN, F.Q. - University Of Chinese Academy Of Sciences; RAN, Q.W. - University Of Chinese Academy Of Sciences; ZHENG, Z.Z. - University Of Chinese Academy Of Sciences; XU, C. - University Of Chinese Academy Of Sciences; CHE, R,X. - Yunnan University; XU, Z.H. - University Of Queensland; CUI, X.Y. - University Of Chinese Academy Of Sciences; HAO, Y.B. - University Of Chinese Academy Of Sciences; WANG, Y.F. - University Of Chinese Academy Of Sciences

Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2022
Publication Date: 4/15/2022
Citation: Li, L., Qian, R., Liu, W., Wang, W., Biederman, J.A., Zhang, B., Kang, X., Wen, F., Ran, Q., Zheng, Z., Xu, C., Che, R., Xu, Z., Cui, X., Hao, Y., Wang, Y. 2022. Drought timing influences the sensitivity of a semiarid grassland to drought. Geoderma. 412. Article 115714. https://doi.org/10.1016/j.geoderma.2022.115714.
DOI: https://doi.org/10.1016/j.geoderma.2022.115714

Interpretive Summary: The impacts of short-term “pulse” droughts lasting several days to weeks are generally negative for grassland ecosystems. However, we lack specific information about how the impacts of drought vary with the timing of the drought during the growing season. Here we conducted a rainfall manipulation experiment imposing drought alternatively during early, middle and late portions of the summer growing season in a semiarid grassland of Inner Mongolia, China. We found that pulse drought occurring during early or mid-growing season had positive impacts on root production, while late-season drought decreased root biomass. Carbon dioxide uptake was most strongly reduced by drought occurring early in the growing season. Collectively, these results suggest that plants faced with drought early in the growing season have reduced capacity to take up carbon through photosynthesis, but they are able to respond to the challenging environment by producing more roots.

Technical Abstract: Quantifying the sensitivity of ecosystems to droughts, particularly with different seasonal timing, could improve our predictions of ecosystem-climate feedbacks, but few experiments have explicitly addressed seasonal timing per se effects on ecosystem sensitivity to droughts. Here, we present a seasonal timing × drought manipulation experiment to examine sensitivity (relative change in response parameters to the relative change in precipitation) of key ecosystem processes (community biomass and ecosystem CO2 fluxes) to pulse-drought with different seasonal timing (early, middle or late) on a temperate semiarid grassland. We found belowground and total biomass were positively sensitive (i.e. ecological processes promoted by droughts and vice versa) to early and middle droughts but negatively sensitive to late drought while aboveground biomass was insensitive to all droughts. Ecosystem CO2 fluxes had the largest negative sensitivity to early drought and smallest negative sensitivity to middle drought, although gross ecosystem production showed larger negative response to droughts than ecosystem respiration, leading to reduction in net ecosystem production, regardless of seasonal timing. Our results highlight the crucial role of seasonal drought timing in regulating sensitivity of key carbon cycle processes to droughts and suggestS that droughts at plant peak stage cause the least disastrous ecological consequences.