Nonlinear, interacting responses to climate limit grassland production under global change.
Global changes in climate, atmospheric composition, and pollutants are altering ecosystems and the goods and services they provide. Among approaches for predicting ecosystem responses, long-term observations and manipulative experiments can be powerful approaches for resolving single-factor and interactive effects of global changes on key metrics such as net primary production (NPP). Here we combine both approaches, developing multidimensional response surfaces for NPP based on the longest-running, best-replicated, most-multifactor global-change experiment at the ecosystem scale-a 17-y study of California grassland exposed to full-factorial warming, added precipitation, elevated CO2, and nitrogen deposition. Single-factor and interactive effects were not time-dependent, enabling us to analyze each year as a separate realization of the experiment and extract NPP as a continuous function of global-change factors. We found a ridge-shaped response surface in which NPP is humped (unimodal) in response to temperature and precipitation when CO2 and nitrogen are ambient, with peak NPP rising under elevated CO2 or nitrogen but also shifting to lower temperatures. Our results suggest that future climate change will push this ecosystem away from conditions that maximize NPP, but with large year-to-year variability.
Department of Global Ecology, Carnegie Institution for Science, Stanford, CA 94305; Department of Biology, Stanford University, Stanford, CA 94305; Department of BioSciences, Rice University, Houston, TX 77005; kai.zhu@rice.edu.
Kai
K
Zhu
Jasper Ridge Biological Preserve, Stanford University, Stanford, CA 94305.
Nona R
NR
Chiariello
Department of Global Ecology, Carnegie Institution for Science, Stanford, CA 94305;
Todd
T
Tobeck
Department of Biology, Stanford University, Stanford, CA 94305;
Tadashi
T
Fukami
Department of Global Ecology, Carnegie Institution for Science, Stanford, CA 94305;
Christopher B
CB
Field
D000393:Air Pollutants; D002140:California; D002245:Carbon Dioxide / Q000378:metabolism; D057231:Climate Change; D017753:Ecosystem; D004784:Environmental Monitoring; D065948:Grassland; D006801:Humans; D009584:Nitrogen / Q000378:metabolism
D000393:Air Pollutants; D002245:Carbon Dioxide; D009584:Nitrogen
California grassland; Jasper Ridge; climate change; ecosystem ecology; global change experiment