Trait Convergence and Plasticity Among Native and Invasive Species in Resource-Poor Environments
2012
Drenovsky, Rebecca E
Functional trait comparisons provide a framework with which to assess invasibility and invasion resistance. Recent research and meta-analyses have produced equivocal results, finding evidence for both trait convergence and trait divergence among coexisting dominant native and invasive species. Research to date lacks information about how multiple stresses may constrain trait values and plasticity and no studies include direct measurements on nutrient conservation traits, which are critical to plants growing in low resource environments. We evaluated the effects of low nutrient and water stress on the growth and allocation, water potential and gas exchange, and nitrogen (N) allocation and use traits of six co-dominant grass species from the Intermountain West of the United States to determine trait values and plasticity. In the greenhouse, we grew our six species under a full factorial combination of high and low N and well-watered and drought conditions. We measured relative growth rate (RGR) and its components, total biomass, biomass allocation, midday water potential, photosynthetic rate, water use efficiency (WUE), green leaf N, senesced leaf N, total N pools, N productivity (NP), and photosynthetic N use efficiency (PNUE). Overall, soil water availability constrained plant responses to N availability and was the major driver of plant traits in our analysis. Drought decreased plant biomass and RGR, limited N conservation, and led to increased WUE. For most traits, native and non-native species were similarly plastic. Conclusions: Our data suggest biomass dominants may converge on functionally similar traits and that biomass dominants, including invasive species, may demonstrate comparable ability to respond to changes in resource availability.
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