Читать книгу North American Agroforestry - Группа авторов - Страница 76

Particularly in arid and semiarid regions, riparian forests are often the only mesic vegetation type and serve a critical role as wildlife habitat. In Arizona and New Mexico, an estimated 80% of all vertebrates are dependent upon riparian habitat for at least part of their life cycle (Johnson, 1989). As linear features in the landscape, riparian forests may serve as corridors for the movement of many species between otherwise isolated patches of habitat (Forman & Godron, 1986). Woody vegetation also plays an integral role in the stabilization of streambanks (Smith, 1976), shading of streams reduces water temperature, and detritus inputs to the stream from the forest provide an energy source as well as habitat structure for aquatic organisms.

Because they occupy low spots in the landscape, riparian forests receive water and water‐borne nutrients and sediment from upland areas, filtering and trapping many of these inputs before they reach the streambed (Lowrance et al., 1984). These forests interact not just with adjacent fields but with systems throughout the landscape, linked through the hydrologic pathways of the watershed. In agricultural regions, this landscape‐level water quality function is particularly important. For example, despite large applications of N fertilizer to corn, peanut (Arachis glabrata Benth.), and other cropland in a Georgia Piedmont watershed, very little N left the watershed in streamflow due in part to accretion of N in the riparian forest biomass and denitrification in the saturated riparian soils (Lowrance, Leonard, Asmussen, & Todd, 1985). Maintenance of a young‐age forest through selective logging can improve the water quality function of the stand by maintaining plant nutrient uptake at a high rate (Welsch, 1991). An excellent overview on the ecological impact of developing riparian forests can be found in Oelbermann, Gordon, and Kaushik (2008).