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Relationships between plant diversity, productivity, and invasion across six North American grasslands.
Emery, Sarah*,1, Christy Bowles, Sandy J. Andelman,2, Elsa E. Cleland, Karen Carney, 3, Drake, John 4, Gramling, Joel 5, Horner-Devine, M. Claire3, Smith, Melinda2, Vandermast, David5, 1 W.K. Kellogg Biological Station, Hickory Corners, MI2 National Center for Ecological Analysis and Synthesis, Santa Barbara, CA3 Stanford University, Stanford, CA4 University of Notre Dame, Notre Dame, IN5 University of North Carolina, Chapel Hill, NC
ABSTRACT- Non-native species can threaten native biodiversity and ecosystem function, making it important to predict where species invasions are most likely. In this study, we investigated how aboveground net primary productivity (ANPP) and total species richness influence the likelihood of invasion by non-native species across multiple community types and years, using data from six North American grasslands (including five LTER sites.) Native and non-native species richness within years were positively correlated at all sites. Total species richness was most often negatively correlated with both ANPP and the proportion of non-native biomass, but relationships and their significance varied among sites and among years. These correlations suggested that while high diversity sites were more likely to be invaded, low diversity sites were more likely to be dominated by non-natives. We also hypothesized that the success of non-natives was related to variation in resource availability in space and time. To separate cause and effect in these observational datasets, we used logistic regression analysis to ask whether variation in ANPP, species richness, or precipitation in one year influenced the abundance or richness of non-natives in the following year. Interannual variation in these parameters differed in their ability to explain invader success in the following year, depending on each site's method for determining species composition, and whether non-native species richness or abundance was used as the response variable. ANPP was consistently negatively related to both the abundance and richness of non-natives in the following year. Precipitation was positively related to the abundance of non-natives in the following year at two sites, and negatively related to non-native abundance at one. Interannual variation in total species richness was significantly related to invader species richness in the following year, but only in sites where permanent plots were used to measure species composition.
Key words: ANPP, meta-analysis, biodiversity, invasibility