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Quantitative data on the abundance and frequency of vascular plants, bryophytes and lichens are lacking for alpine snowbed and rill communities in northeastern North America. Such data are needed to establish whether the communities are changing in response to climate warming, nitrogen deposition or shifts in the timing of precipitation and snowmelt. We surveyed nine sites (five snowbeds and four rills) on Mount Washington (White Mountain National Forest, New Hampshire), recording 54 vascular plant species, 42 bryophytes and 13 lichens. Although vascular plants were most abundant, bryophytes and lichens, which had not been completely surveyed in these communities previously, were important in terms of species richness (as many as eight bryophytes and four lichens in 1 m2 quadrats) and were occasionally abundant, particularly bryophytes in rills. We found that snowbeds and rills are separate communities. Some species are shared, but far higher numbers of vascular plants, bryophytes and lichens were found in one community but not the other. The most frequent vascular plants had been reported as common in snowbeds and rills previously. However, several species that are common in these communities elsewhere occurred less often in our sites because of variation occurring both across the region and within the White Mountains. Our research provides baseline information on snowbeds and rill plant communities so that future studies can determine how they respond to changes in environmental conditions.
Herbivory by deer is one of the leading biotic disturbances on forest understories (i.e., herbs, small shrubs, and small tree seedlings). A large body of research has reported declines in height, abundance, and reproductive capacity of forbs and woody plants coupled with increases in abundance of graminoids, ferns, and exotic species due to deer herbivory. Less clear is the extent to which (and the direction in which) deer alter herbaceous layer diversity, where much of the plant diversity in a forest occurs. We examined the effect of 15 y of deer exclusion on the understory of a suburban hardwood forest in Connecticut exposed to decades of intensive herbivory by white-tailed deer (Odocoileus virginianus). We compared species richness (at subplot and plot scale), individual species and life form group abundance (% cover), and community composition between grazed and exclosure plots, as well as between mesic and wet soil blocks. Forb cover was more than twice as abundant in exclosure as in grazed plots, whereas sedge (Carex spp.) cover was 28 times more abundant, and exotic species cover generally higher in grazed than in exclosure plots. Native and exotic species richness were both higher in grazed than exclosure plots at the subplot scale, and native herbaceous richness was higher in grazed plots at both spatial scales. In contrast, native shrub richness increased with deer exclusion at the plot scale. Our results suggest that deer exclusion had contrasting effects on species richness, depending on plant life form, but that overall richness of both exotic and native plants declined with deer exclusion. In addition, site heterogeneity remained an important driver of vegetation dynamics even in the midst of high deer densities.