Fire increases ecosystem sensitivity to precipitation through conversion from shrubland to annual grassland

Journal of Ecology, vol. 114

Abstract

Abstract Drylands face interrelated threats from invasion, altered fire regimes and climate change. In the Great Basin of the western U.S., more frequent fires are increasing the cover of invasive annual grasses and amplifying the grass‐fire cycle, wherein annual grasses build up fine fuels that lead to more fires. At the same time, rainfall in this region is projected to become more variable from year to year. As these changes can interact, it remains unclear how the combined effects of fire, plant community change and precipitation variability will alter net primary production (NPP). Here we assessed how fire has shifted the response of NPP to precipitation amount in the northern Great Basin between 1986 and 2015. We then asked whether changes in NPP response to precipitation (hereafter referred to as the precipitation‐NPP relationship) were driven by changes in the plant community. Finally, we assessed how fire altered climatic and elevational controls on precipitation‐NPP relationships. We used a quasi‐experimental approach combining difference‐in‐difference and matching methods to analyse remotely sensed cover, production and burn occurrence datasets with interpolated precipitation values across the 30‐year time series. We found that precipitation‐NPP relationships changed following fire: burned areas tended to be more productive for a given unit of precipitation, and NPP was more sensitive to interannual variation in precipitation after a fire compared to before a fire. These shifts in precipitation‐NPP relationships were mediated by shifts in community composition, primarily through increases in herbaceous annual cover. Additionally, fire led to greater changes in these relationships at higher elevations. Synthesis . These results highlight how fire can magnify the effects of increasingly variable precipitation on ecosystem functioning and amplify fire hazard in dryland ecosystems.

Authors 7

1. Thomas K. Merchant corresponding

   Institute of Arctic and Alpine Research · University of Colorado Boulder

   Affiliation as printed

   Department of Ecology and Evolutionary Biology University of Colorado Boulder Boulder Colorado USA

   Institute of Arctic and Alpine Research University of Colorado Boulder Boulder Colorado USA

2. Elisa Van Cleemput Aachen

   Leiden University

   Affiliation as printed

   Leiden University College The Hague Leiden University Den Haag The Netherlands

3. Andrew J. Felton

   Montana State University

   Affiliation as printed

   Department of Land Resources and Environmental Sciences Montana State University Bozeman Montana USA

4. Peter B. Adler

   Utah State University

   Affiliation as printed

   Department of Wildland Resources and the Ecology Center Utah State University Logan Utah USA

5. Laura E. Dee

   University of Colorado Boulder

   Affiliation as printed

   Department of Ecology and Evolutionary Biology University of Colorado Boulder Boulder Colorado USA

6. Michael J. Koontz

   University of Colorado Boulder

   Affiliation as printed

   Earth Lab University of Colorado Boulder Boulder Colorado USA

7. Katharine N. Suding

   Institute of Arctic and Alpine Research · University of Colorado Boulder

   Affiliation as printed

   Department of Ecology and Evolutionary Biology University of Colorado Boulder Boulder Colorado USA

   Institute of Arctic and Alpine Research University of Colorado Boulder Boulder Colorado USA