Plant growth and aboveground production respond differently to late-season deluges in a semi-arid grassland
Semi-arid ecosystems are strongly water-limited and typically quite responsive to changes in precipitation amount and event size. In the C4-dominated shortgrass steppe of the Central US, previous experiments suggest that large rain events more effectively stimulate plant growth and aboveground net primary production (ANPP) than an equal amount of precipitation from smaller events. Responses to naturally occurring large events have generally been consistent with experimental results, with the exception of large events occurring later in the growing season (e.g., August). These have been reported as less effective at increasing net C uptake, despite temperatures optimal for C4 plant growth. Since atmospheric warming is increasing the frequency of statistically extreme rain events (deluges) throughout the growing season, how late-season deluges affect semi-arid ecosystems remains to be resolved. We applied deluges in August of three sizes (1.0–2.5 times average August precipitation) to assess the potential for late-season deluges to stimulate plant growth and ANPP. These late-season deluges led to significant “green-up” of this grassland, with new leaf production, and an increase in flowering of the dominant grass species. Further, these responses increased as deluge size increased, suggesting that larger or multiple deluges may lead to even greater growth responses. However, despite strong plant-level responses, no increase in ANPP was measured. Our results confirm that aboveground plant growth in the C4-dominated shortgrass steppe does respond to late-season deluges; however, if there is an increase in plant biomass, net accumulation aboveground is minimal at this time of year.
KeywordsANPP Climate change Greenness Precipitation Shortgrass steppe
Funding for this research was provided by a National Science Foundation Graduate Research Fellowship (NSF GRF) awarded to A. Post and a United States Department of Agriculture National Institute of Food and Agriculture (NSF NIFA) Award # 2018-67019-27849. The authors thank the USDA-ARS Central Plains Experimental Range (CPER) for providing space and logistical support for this experiment.
Author contribution statement
AKP and AKK conceived and designed the experiment. AKP conducted the fieldwork and analyzed the data. AKP wrote the initial draft of the manuscript and both AKP and AKK edited the subsequent versions.
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