Daniel E. Winkler
Robin H. Reibold
Brooke Bossert Osborne
Sasha C. Reed
Michala Lee Phillips
2021
<div id="Abs1-section" class="c-article-section"><div id="Abs1-content" class="c-article-section__content"><p>Anthropogenic nitrogen (N) deposition is significantly altering both community structure and ecosystem processes in terrestrial ecosystems across the globe. However, our understanding of the consequences of N deposition in dryland systems remains relatively poor, despite evidence that drylands may be particularly vulnerable to increasing N inputs. In this study, we investigated the influence of 7 years of multiple levels of simulated N deposition (0, 2, 5, and 8 kg N ha<sup>−1</sup> year<sup>−1</sup>) on plant community structure and biological soil crust (biocrust) cover at three semi-arid grassland sites spanning a soil texture gradient. Biocrusts are a surface community of mosses, lichens, cyanobacteria, and/or algae, and have been shown to be sensitive to N inputs. We hypothesized that N additions would decrease plant diversity, increase abundance of the invasive annual grass<span> </span><i>Bromus tectorum,</i><span> </span>and decrease biocrust cover. Contrary to our expectations, we found that N additions did not affect plant diversity or<span> </span><i>B. tectorum</i><span> </span>abundance. In partial support of our hypotheses, N additions negatively affected biocrust cover in some years, perhaps driven in part by inter-annual differences in precipitation. Soil inorganic N concentrations showed rapid but ephemeral responses to N additions and plant foliar N concentrations showed no response, indicating that the magnitude of plant and biocrust responses to N fertilization may be buffered by endogenous N cycling. More work is needed to determine N critical load thresholds for plant community and biocrust dynamics in semi-arid systems and the factors that determine the fate of N inputs.</p></div></div><div id="cobranding-and-download-availability-text" class="note test-pdf-link"><br></div>
application/pdf
10.1007/s00442-020-04841-3
en
Springer
Muted responses to chronic experimental nitrogen deposition on the Colorado Plateau
article