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Title: Semiarid ecosystem sensitivity to precipitation extremes: weak evidence for vegetation constraints

In semiarid regions, vegetation constraints on plant growth responses to precipitation (PPT) are hypothesized to place an upper limit on net primary productivity (NPP), leading to predictions of future shifts from currently defined linear to saturatingNPPPPTrelationships as increases in both dry and wetPPTextremes occur. We experimentally tested this prediction by imposing a replicated gradient of growing seasonPPT(GSP,n = 11 levels,n = 4 replicates), ranging from the driest to wettest conditions in the 75‐yr climate record, within a semiarid grassland. We focused on responses of two key ecosystem processes: abovegroundNPP(ANPP) and soil respiration (Rs).ANPPandRsboth exhibited greater relative responses to wet vs. dryGSPextremes, with a linear relationship consistently best explaining the response of both processes toGSP. However, this responsiveness toGSPpeaked at moderate levels of extremity for both processes, and declined at the most extremeGSPlevels, suggesting that greater sensitivity ofANPPandRsto wet vs. dry conditions may diminish under increased magnitudes ofGSPextremes. Underlying these responses was rapid plant compositional change driven by increased forb production and cover asGSPtransitioned to extreme wet conditions. This compositional shift increased the magnitude ofANPPresponses to wetGSPextremes, as well as the slope and variability explained in theANPPGSPrelationship. Our findings suggest that rapid plant compositional change may act as a mediator of semiarid ecosystem responses to predicted changes inGSPextremes.

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Author(s) / Creator(s):
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Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Medium: X
Sponsoring Org:
National Science Foundation
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