Читать книгу North American Agroforestry - Группа авторов - Страница 101

The ecological interaction among components in temperate agroforestry systems is a broad topic to cover in a single chapter; however, some generalizations can be made based on the available literature. For example, even though the impacts of competition for light, water, and nutrients can be difficult to separate for a given system due to temporal changes in climate, level of fertilization, and the varying effects that both species diversity and species size have on a system, crop production is typically decreased in areas immediately surrounding trees in agroforestry systems. In some cases, however, such as with shelterbelts, trees can have a positive impact on overall crop production or, in the case of silvopastoral systems, improve the quality of forage despite the decrease in forage production. Even though crop yields may be decreased compared with monocultural systems, by incorporating multiple species in a single system there is a possibility to increase the overall biomass production and economic value.

In addition to the potential for increased production from agroforestry systems compared with conventional agriculture, there are other potential benefits of agroforestry systems. For example, evidence supporting the safety net role of trees in temperate alley‐cropping systems shows both a reduction in the contamination of surface and subsurface water and a reduced competition for nutrients. Furthermore, this safety net effect can also be seen in woody riparian buffer strips, which can be incorporated into any agricultural system, including conventional agriculture.

Several information gaps still exist that need immediate attention by the scientific community. These vary from quantifying the interactive effects of multiple resources on system productivity to studying broader landscape‐level interactions of agroforestry systems within the landscape matrix. Despite these limitations, there is evidence that competition for light, water, and nutrients, in combination with other factors, such as allelopathy, can be managed through both the design and maintenance of agroforestry systems so that the competitive influence is minimized while the facilitative influence is maximized. This offers promise to the long‐term ecological sustainability of agroforestry systems.