•  
  •  
 

Document Type

Feature Article

First Page

3

Last Page

19

Abstract

Non-native species invasions in national parks directly interfere with the major management goal of protecting native biota. The status of species richness and non-native invasions was assessed in five riparian vegetation types in Grand Teton National Park, Wyoming, with nested-scale number and frequency vegetation data using a Modified­Whittaker sampling design. In the 20 (1OOO-m2 plots sampled, non-native species represented 11.9% (35) of the total 294 species recorded. Non-native species were found in small populations either widely dispersed across the five vegetation types or appearing to have some level of habitat specificity. Total species richness across the five vegetation types varied from 42 species in the sage community to 96 species in the conifer-broadleaf community. Overall, mean species richness across the five communities was 81.9 species/0.1 ha. A suite of environmental variables such as nutrient availability, flood regime, herbivory as well as successional trends may explain the variability in species richness across communities. Patterns of total species richness across multiple scales were fairly consistent. Patterns of non-native species invasion, however, appeared to be both scale and vegetation type dependent. The highest proportion of non-native species for four of the five vegetation types was recorded at the smaller sampling scales. The alder community was the most invaded at all scales measured and had the most distinct assemblage of non-native species. Some studies suggest that community invasibility may be related to species richness. At the 1-m2 and 1000- m2 scales, total species richness and number of non-native species were significantly and positively correlated. When the alder sites were removed from analysis at the 1000- m2 scale, the positive linear relationship increased, and the total variance explained by the linear models was enhanced by 38%. At all scales sampled, the alder sites were highly and disproportionately invaded, often more than twice the level of other communities. The mechanism of nitrogen fixation may be promoting non-native invasions in the alder community. At the vegetation type scale (combined species lists from four 1OOO-m2 plots in each community), those communities with the most unique non-native assemblages were the most invaded. A significant negative linear relationship between non­native species overlap and percentage of non-native species was observed in the alder sites at each scale sampled. This pattern suggests some relationship between properties of an invading species and properties of the community that it invades. Because the results of this study suggest species rich riparian landscapes are vulnerable to non-native invasions, recommendations are offered to assist managers in responding efficiently and effectively to this conservation priority.

Share

COinS