Evol Ecol Res 19: 279-297 (2018)     Full PDF if your library subscribes.

The role of climate in the dynamics of annual plants in a Chihuahuan Desert ecosystem

Danielle D. Ignace¹, Nancy Huntly² and Peter Chesson^3,4

¹Department of Biological Sciences, Smith College, Northampton, Massachusetts, USA, ²Ecology Center and Department of Biology, Utah State University, Logan, Utah, USA, ³Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, USA and ⁴Department of Life Sciences and Center of Global Change Biology, National Chung Hsing University, Taichung, Taiwan

Correspondence: D.D. Ignace, Department of Biological Sciences, Smith College, Ford Hall, Northampton, MA 01063, USA. email: dignace@smith.edu

ABSTRACT

Question: What is the role of temporal climate fluctuations in the dynamics of desert winter annual plants in the Portal Bajada, and in the sustained irruption of the non-native annual plant species, Erodium cicutarium?

Field site: Portal Bajada, San Simon Valley, Arizona, USA.

Methods: We counted plants at flowering over a 21-year period on twelve permanent plots and related these numbers to weather data collected at an on-site weather station, supplemented by observations from the National Climate Data Center. Specific summary climate variables considered most relevant to annual plant biology were developed as candidate predictors of plant response variables.

Statistical techniques: We removed trends in the data associated with the irruption of E. cicutarium, removed temporal autocorrelation, and applied a technique that sought the strongest climatic predictors of vegetation response variables by testing climate variables against each other in bivariate regression analyses. The validity of this technique was demonstrated by simulation. We supplemented our analysis with multivariate regression for simultaneous tests on multiple response variables.

Conclusions: Winter rainfall was the strongest predictor of total annual plant abundance, but number of species was more strongly predicted by average temperature over the total growing season (fall and winter), with cooler weather favouring more species. Average size of a rainfall event, although often thought important in desert plant biology, did not emerge as a significant predictor of the community-level variables, total abundance and number of species, but winter event size did emerge as a significant predictor of differences between the abundances of native species. Our analyses do not support a role for climate in the sustained irruption of E. cicutarium.

Keywords: Chihuahuan Desert, climate change, Erodium cicutarium, global warming, non-native invasives, seasonal precipitation, species diversity.

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