Summary 1.In mountainous regions, road construction is accompanied by large-scale physical disturbance associated with cut and fill operations that drastically alter the landscape. Cut operations remove soil and rock from the hillside above the proposed road, while soil and rock are deposited on the down-slope area in fill operations. The resultant roadsides are highly disturbed habitats characterized by plant communities maintained at an early successional stage. They are often planted with non-native species and frequently provide vectors for the introduction and spread of invasive species. Public transportation managers need to balance the rapid revegetation of roadsides with the goal of maximizing use of native species and minimizing the introduction of non-native species. 2. This study examined vegetation-site relationships along 13 major four-lane highways in West Virginia, USA, using analysis of variance, multiresponse permutation procedures and indicator species analysis. 3. Mean soil nutrient values showed some differences with respect to highway, but fewer when highway positions were compared. Similarly, when highway position was considered, there were no significant differences in mean plant species richness, evenness or diversity. 4. Results of multiresponse permutation procedures suggested that different highways may be characterized by distinct vegetation assemblages. This hypothesis was supported by indicator species analysis: 54 species showed a statistically significant ( P < 0·05) affinity to one highway over all others. More than half of these were classified as non-native and exotic invasive species. When highway position was considered, no significant differences in community composition were found, and indicator species analysis found only 25 species that exhibited a significant affinity to one type of position. Of these, only eight were exotic. 5. Of the 33 most abundant herbaceous species, 11 showed a significant relationship between cover and distance from pavement. For all but one, average cover declined in a linear fashion with increasing distance. 6. Synthesis and applications . Despite extensive topographic disturbance associated with highway construction, the resultant vegetative communities do not differ with respect to type of construction or resultant landform. This suggests that highway agencies can manage roadside vegetation using similar, standard techniques. Roadsides are optimal growing sites for exotic invasive species that out-compete native vegetation. Management goals should therefore include techniques for limiting the establishment of these species, and substitution of non-native species planted for erosion control with suitable native species.

No abstract

Beavers (Castor canadensis) can cause dramatic changes in vegetative composition and diversity. Although alterations by beaver have been studied extensively, little attention has been paid to the effects beaver impoundments have on rare plants. Effective conservation of riparian and wetland rare plant species must consider the responses of vegetation to changes in hydrology that can occur when beaver populations are present. The goal of this research was to establish the occurrence of locally rare plant species, examine community composition, and analyze vegetative community structure of vegetation associated with beaver ponds in Canaan Valley, West Virginia, USA. Species richness and diversity were similar between plots located inside beaver ponds and adjacent to beaver ponds (P [ 0.05). Although no significant difference in rare plant species was detected among pond ages, the oldest ponds ([56 years) had twice as many rare species as the youngest ponds (B6 years). The youngest ponds had higher overall mean species richness (S) than ponds 7-56 years old (P \ 0.05), but S returned to similar levels in the oldest ponds. Of the 15 rare species observed, most were classified as obligate (9) or facultative wetland (4) species. The youngest ponds contained the fewest number of rare species. Multiple response permutation procedure (MRPP) analyses of community structure detected no relation between community composition and either pond age or size. However, both MRPP and nonmetric multi-dimensional scaling showed proximity to pond was important in herbaceous community structure. Wetlands in beaver ponds also were shown to be distinct from adjacent wetland areas. Conservation of existing beaver populations is necessary so that the entire spectrum of pond ages is available for the maintenance of rare plant species and communities.

Bioassessment methods for wetlands, and other bodies of water, have been developed worldwide to measure and quantify changes in "biological integrity." These assessments are based on a classification system, meant to ensure appropriate comparisons between wetland types. Using a local site-specific disturbance gradient, we built vegetation indices of biological integrity (Veg-IBIs) based on two commonly used wetland classification systems in the USA: One based on vegetative structure and the other based on a wetland's position in a landscape and sources of water. The resulting class-specific Veg-IBIs were comprised of 1-5 metrics that varied in their sensitivity to the disturbance gradient (R2=0.14-0.65). Moreover, the sensitivity to the disturbance gradient increased as metrics from each of the two classification schemes were combined (added). Using this information to monitor natural and created wetlands will help natural resource managers track changes in biological integrity of wetlands in response to anthropogenic disturbance and allows the use of vegetative communities to set ecological performance standards for mitigation banks.

No abstract