Seasonal and individual event-responsiveness are key determinants of carbon exchange across plant functional types
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PHYSIOLOGICAL ECOLOGY – ORIGINAL RESEARCH
Seasonal and individual event‑responsiveness are key determinants of carbon exchange across plant functional types Daniel E. Winkler1 · Jayne Belnap1 · Michael C. Duniway1 · David Hoover2 · Sasha C. Reed1 · Hannah Yokum3 · Richard Gill3 Received: 5 March 2020 / Accepted: 20 July 2020 © This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2020
Abstract Differentiation in physiological activity is a critical component of resource partitioning in resource-limited environments. For example, it is crucial to understand how plant physiological performance varies through time for different functional groups to forecast how terrestrial ecosystems will respond to change. Here, we tracked the seasonal progress of 13 plant species representing C3 shrub, perennial C 3 and C 4 grass, and annual forb functional groups of the Colorado Plateau, USA. We tested for differences in carbon assimilation strategies and how photosynthetic rates related to recent, seasonal, and annual precipitation and temperature variables. Despite seasonal shifts in species presence and activity, we found small differences in seasonally weighted annual photosynthetic rates among groups. However, differences in the timing of maximum assimilation (Anet) were strongly functional group-dependent. C3 shrubs employed a relatively consistent, low carbon capture strategy and maintained activity year-round but switched to a rapid growth strategy in response to recent climate conditions. In contrast, grasses maintained higher carbon capture during spring months when all perennials had maximum photosynthetic rates, but grasses were dormant during months when shrubs remained active. Perennial grass Anet rates were explained in part by precipitation accumulated during the preceding year and average maximum temperatures during the past 48 h, a result opposite to shrubs. These results lend insight into diverse physiological strategies and their connections to climate, and also point to the potential for shrubs to increase in abundance in response to increased climatic variability in drylands, given shrubs’ ability to respond rapidly to changing conditions. Keywords Photosynthesis · Drought · Ecophysiology · Colorado Plateau · Water-use efficiency
Introduction
Communicated by Susanne Schwinning. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00442-020-04718-5) contains supplementary material, which is available to authorized users. * Daniel E. Winkler [email protected] 1
U.S. Geological Survey, Southwest Biological Science Center, Moab, UT 84532, USA
2
Rangeland Resources and Systems Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Fort Collins 80526, USA
3
Department of Biology, Brigham Young University, Provo, UT 84604, USA
Quantifying seasonal patterns of photosynthetic rates allows us to examine and estimate the timing and amount of carbon that goes into a
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