, Volume 184, Issue 1, pp 267–277 | Cite as

Chronic N enrichment and drought alter plant cover and community composition in a Mediterranean-type semi-arid shrubland

Community ecology – original research


Anthropogenic nitrogen (N) deposition has caused a decline in native plant species and an increase in exotic plant species in many terrestrial ecosystems; however, vegetation change depends on the rate and/or duration of N input, individual species responses, interactions with other resources, and ecosystem properties such as species richness and canopy cover, soil texture, pH, and/or disturbance regime. Native shrub and exotic forb responses to N enrichment were evaluated over a 13-year field experiment in a mature coastal sage scrub (CSS) shrubland of southern California to test the hypothesis that dry-season N input will cause a decline in native shrubs and an increase in exotic annuals. Nitrogen enrichment caused the dominant native shrubs, Artemisia californica and Salvia mellifera, to respond differently, with A. californica initially increasing with N input but declining thereafter and S. mellifera declining consistently over the 13-year-period. Both species exhibited higher canopy dieback during drought conditions, especially in N plots. Brassica nigra, an exotic annual, invaded N plots significantly more than control plots, but only after 10 years of N addition and a prolonged drought, which increased native shrub canopy dieback. These results indicate a possible synergism between N enrichment and drought on native shrub and exotic forb abundance, which would have important implications for plant diversity in semi-arid shrublands of southwest US that are anticipated to experience an increase in anthropogenic N enrichment and the frequency and duration of drought.


Anthropogenic N deposition Chaparral Climate change Coastal sage scrub Exotic species invasion 



This research was supported in part by the National Science Foundation-CAREER (DEB-0133259), National Institutes of Health- National Institute of General Medical Science-SCORE (S06 GM 59833), and the United States Department of Agriculture-National Institute of Food and Agriculture-HSI (2010-38422-21241) programs. Permission to use the Santa Margarita Ecological Reserve was graciously granted by the San Diego State University Field Station Programs.

Author contribution statement

GLV conceived, designed, and performed the experiments, analyzed the data, and wrote the manuscript.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2017

Authors and Affiliations

  1. 1.California State UniversitySan MarcosUSA

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