Читать книгу North American Agroforestry - Группа авторов - Страница 91

Agroforestry practices, by increasing structural and compositional plant diversity on the landscape, provide improved wildlife habitat for many species. In some agriculture‐dominated landscapes, windbreaks and riparian buffers offer the only woody habitat for wildlife (Johnson & Beck, 1988; Söderström, Svensson, Vessby, & Glimskär, 2001). Brandle et al. (2004) reported that in Nebraska, landowners identified wildlife as a primary reason for the establishment of windbreaks on agricultural land. In a comparison of maize monoculture with riparian buffer plantings of ladino clover (Trifolium repens L.) and orchardgrass with three tree species—green ash (Fraxinus pennsylvanica Marsh.), black walnut, and red oak—Gillespie, Miller, & Johnson (1995) showed that the riparian strips provided better habitat for birds than maize monoculture, with both higher bird densities and diversity.

Gibbs et al. (2016), in their study in Ontario, Canada, found that tree‐based intercropping systems enhanced avian species diversity compared with old fields and monocropped areas. When a pasture is converted to agroforestry, birds normally associated with woodlands are being attracted to agroforestry and, along with birds normally found in open fields, create a unique assemblage of species. Mcadam, Sibbald, Teklehaimanot, and Eason (2007) examined the effect of temperate silvopastoral systems on certain invertebrate groups, including carabid beetles and spiders, and on the number of individuals and species of birds. They reported that the presence of trees on grasslands attracted invertebrates, which might have provided an enhanced food supply, which attracted birds. They concluded that, even at an early stage, silvopastoral systems had a positive impact on birds and could significantly enhance biodiversity.

Bobryk et al. (2016) demonstrated that the overall acoustic complexity index (ACI), a measure of species richness based on the sonic environment, was higher for a pecan alley‐cropping system and a silvopasture system than a soybean monoculture in Missouri. There was a weak but significant relationship (R² = .30) between the ACI and overall structural complexity across different land‐use systems. The sound sources identified included birds, amphibians, insects, and mammals. They concluded that habitat heterogeneity created by agroforestry was the reason for the acoustic and thereby species diversity observed in their study.