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Effects of Nitrogen and Salinity on Growth and Competition Between a Native Grass and an Invasive Congener
Authors:Annette Kolb  Peter Alpert
Institution:(1) Plant Biology Graduate Program, University of Massachusetts, Amherst, MA 01003-9297, USA;(2) Department of Ecology and Evolutionary Biology, FB2, University of Bremen, Leobener Str., 28359 Bremen, Germany;(3) Department of Biology, University of Massachusetts, Amherst, MA 01003-9297, USA
Abstract:Numerous studies show that an increase in the availability of limiting resources can increase invasion by non-native plants into natural communities. One possible explanation is that the ability of natives to compete with non-natives tends to decrease when resource availability is increased. We tested this hypothesis in a competition experiment using two closely matched plant species and two environmental factors related to limiting resources in a coastal grassland system on Bodega Head in northern California. We grew the native grass Bromus carinatus and the non-native grass B. diandrus together and apart at different levels of soil nitrogen crossed with different levels of soil salinity. Both species are abundant in the grassland and previous work suggested that the abundance of B. carinatus is lower and the abundance of B. diandrus is higher on soil that has been enriched with nitrogen. Salinity has been shown to be negatively associated with invasion by B. diandrus into another California grassland, and to vary significantly over short distances in the grassland at Bodega Head, where it could affect water availability, which strongly limits plant growth during the dry season. Contrary to our prediction that low resource availabilities would increase the relative competitive ability of the native, the ability of B. carinatus to compete with B. diandrus was not greater when nitrogen availability was lower or when soil salinity was higher. Instead, high salinity increased the relative competitive ability of the non-native, and low nitrogen had little effect on competition. This suggests that preventing resource enrichment will not suffice to control invasion by non-native plant species in this grassland.
Keywords:Bromus carinatus  Bromus diandrus  California coastal prairie  non-native plant species  salt tolerance
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