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Wetlands and Urbanization: Implications for the Future

作者:
" " by Amanda Azous and Richard R. Horner
ISBN :
1566703867
出版日期:
2010-10-06 00:00:00
语言:
国家地区:
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Terrestrial Small Mammal Distribution, Abundance, and Habitat Use211have been identid within the greatest diversity of plant communities and stand conditions of any small mammal in the Northwest.21 Nevertheless, it may be that native mice preferentially select wetlands. Riparian-associated upland red alder communities are often dominated by deer mice, whereas in upland forests they are only the third most abundant species after the Trowbridge shrew and creeping vole.10,18 Interestingly, other species we captured such as the Townsend vole, Paci jumping mouse, marsh shrew, and long-tailed vole, were found by other investigators to be more abundant along riparian corridors than in adjacent upland areas of coniferous stands.16, 17 Native mice most likely play a disproportionately important role in the trophic dynamics of palustrine wetlands because we found them at almost all sites, capturing them on a regular basis and in large numbers when compared to other small mammals. Although other species breed throughout the year (e.g., Townsend vole, creeping vole) their abundances were never as great, thus their ecological role may not be as important. Several species of voles were captured. Townsend vole populations reach highest abundances in the wet ld and meadow environments of the Puget Sound lowlands.10 They are often found in grassy areas interspersed with sedges and rushes and, in fact, sometimes live in lawns adjacent to such areas.6 Consequently, their limited distribution and low abundances at our surveyed wetlands is disturbing since they inhabit areas with high water tables. Although our captures are few, it is interesting that we did not capture longtailed voles at wetlands where we captured the Townsend vole. Some believe the Townsend vole may be more aggressive and hence may not be sympatric with longtailed voles.6 Creeping voles may be found in a variety of environments but often are found at wetlands because their preferred breeding, feeding, and resting habitats are riparian plant communities and especially wet meadows. However, they are also associated with forests and are abundant where forests have been cut.6,10 Long-tailed voles, although arboreal, were captured in relatively large numbers at our wetlands. Long-tailed voles are found in grass and forb communities of wetlands and have been captured in riparian zones.6 Southern red-backed voles are generally found in coniferous forests with substantial amounts of large fallen trees and around openings in such forests.10 We found southern-red-backed voles at only one wetland that exhibited these traits, but not in the seven other wetlands that generally exhibited such forest structure. Its absence from these potential sites remains unexplored. The richness and abundance of shrews at wetlands may be attributable to their small size, high metabolic rates, and correspondingly high water losses, requiring them to remain within high moisture environments.21-23 In fact, research shows that hydric habitats supported 2.7 times as many shrew species (x = 4.7) as xeric habitats (x = 1.8 species).24 In the Paci Northwest, water and moisture may not be a limiting factor with the exception the of summer drought periods. Consequently, our shrew richness may be similar to that identid for uplands.10 Also, in contrast to expectations, the vagrant shrew reaches its greatest abundances in exposed environments and, in fact, increases in number with clearcut area and mean clearcut patch size.10 Moreover, the Trowbridge shrew is an omnivorous shrew that occupies the greatest
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