Читать книгу North American Agroforestry - Группа авторов - Страница 57

A final issue to discuss is mosaics of monocultures in agricultural landscapes. Common features of agricultural landscapes throughout the United States and Canada are single‐crop farm fields, woodlots and tree plantations, wetlands, and grazing lands. A physical proximity does not constitute agroforestry at the landscape level because there is no intentional integration and there is minimal interaction among components. In contrast, an agricultural landscape that contains windbreaks or riparian and upland buffers, that is, linear plantings including permanent woody vegetation strategically placed to maximize conservation benefits and create biophysical interactions with other components of the agricultural system, clearly demonstrates agroforestry at a landscape scale. The subject is discussed further in Table 2–3, which outlines agroforestry concepts.

Table 2–3. Agroforestry concepts.

Concepts/Comments

Cascades of benefits are derived from beneficial process‐level biophysical interactions created when trees and/or shrubs are deliberately combined with crops and/or livestock.

Additional benefits are often derived from component integration when compared with traditional, segregated (agriculture and forestry) production. Through intensive and careful management, desired interactions are optimized and undesirable interactions are minimized. Agroforestry practices introduce, restore, and enhance biological diversity and agroecosystem resilience at field, farm, watershed and landscape levels.

For many people, enhanced biodiversity is considered a benefit, e.g., increased wildlife; however, in agricultural regions, biodiversity must be managed to obtain desired effects like enhancement of selected fish, wildlife, and plant species. The challenge is to determine the type, amount and distribution of species that will provide an adequate level of desired benefits.

Agroforestry contributes to integrated pest management by creating favorable habitats and microclimates to enhance the extent and effectiveness of natural pest controls.

Agroforestry is an essential component of effective conservation buffers creating positive impacts upon steep slopes, highly‐erodible soils and collapsing streambanks.

Agroforestry contributes to the maintenance of soil quality and productivity by keeping soil in place, enhancing nutrient absorption and cycling, intercepting water‐borne pollutants, improving water filtration and retention capacity, and reducing flood damage.

Agroforestry increases the productive area of the farm by expanding use of vertical and horizontal space above‐ and below‐ground and fully exploiting the diversity of useable niches.

Agroforestry practices permit fuller use of the soil profile, maximize use of photosynthetic radiation, and lengthen the growing season.

Agroforestry practices exploit additional field scale niches including border areas, marginal sites (rocky, infertile, too wet or dry) and steep slopes.