Global change effects on B romus tectorum L . ( P oaceae) at its high‐elevation range margin

• Published in: Global change biology 2013-01, Vol.19 (1), p.161-172
• Main Authors: Concilio, Amy L., Loik, Michael E., Belnap, Jayne
• Format: Article
• Language: English
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.12032

Global change is likely to affect invasive species distribution, especially at range margins. In the eastern S ierra N evada, C alifornia, USA , the invasive annual grass, B romus tectorum , is patchily distributed and its impacts have been minimal compared with other areas of the I ntermountain W est. We used a series of in situ field manipulations to determine how B . tectorum might respond to changing climatic conditions and increased nitrogen deposition at the high‐elevation edge of its invaded range. Over 3 years, we used snow fences to simulate changes in snowpack, irrigation to simulate increased frequency and magnitude of springtime precipitation, and added nitrogen (N) at three levels (0, 5, and 10 g m −2 ) to natural patches of B . tectorum growing under the two dominant shrubs, A rtemisia tridentata and P urshia tridentata, and in intershrub spaces ( INTR ). We found that B . tectorum seedling density in A pril was lower following deeper snowpack possibly due to delayed emergence, yet there was no change in spikelet production or biomass accumulation at the time of harvest. Additional spring rain events increased B . tectorum biomass and spikelet production in INTR plots only. Plants were primarily limited by water in 2009, but colimited by N and water in 2011, possibly due to differences in antecedent moisture conditions at the time of treatments. The threshold at which N had an effect varied with magnitude of water additions. Frequency of rain events was more influential than magnitude in driving B . tectorum growth and fecundity responses. Our results suggest that predicted shifts from snow to rain could facilitate expansion of B . tectorum at high elevation depending on timing of rain events and level of N deposition. We found evidence for P‐limitation at this site and an increase in P‐availability with N additions, suggesting that stoichiometric relationships may also influence B . tectorum spread.