North American Agroforestry. Группа авторов. Читать онлайн. Newlib. NEWLIB.NET

Автор: Группа авторов
Издательство: John Wiley & Sons Limited
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Жанр произведения: Биология
Год издания: 0
isbn: 9780891183839
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12.6 c 15.7 b 19.6 a ‘Justus’ orchardgrass 19.8 a 16.7 a 18.5 a ‘Manhatten II’ ryegrass 15.3 b 16.0 b 18.8 a Smooth bromegrass 16.7 c 18.1 b 20.2 a ‘KY31’ tall fescue 14.0 b 15.0 b 18.1 a ‘Martin’ tall fescue 14.3 b 15.5 b 18.5 a Timothy 15.4 c 17.6 b 20.4 a

      Note. Means followed by the same letter within a row are not significantly different (Tukey’s Studentized range test, α = 0.05).

      In addition to their effect on solar radiation, trees can also influence the microclimate of the surrounding area in terms of wind speed and humidity. Serving as windbreaks, trees slow the movement of air, thereby reducing evaporative stress. For example, in a silvopastoral system in Australia, wind speed was reduced up to 80% in a zone that extended 5H upwind and 25H downwind of the windbreak (where H is the height of the windbreak) (Cleugh, 2002). Windbreaks have also been shown to reduce evapotranspiration, improve the distribution and utilization of irrigation water, and improve crop water use efficiency (Davis & Norman, 1988). As shown in several studies, the wind reduction and improved microclimate resulting from planting windbreaks or shelterbelts in crop fields may translate into improved crop quality and yield within the sheltered areas (10–15H), (Brandle, Hodges, & Zhou, 2004; Kort, 1988). These effects, however, may vary with annual rainfall conditions (Rivest & Vézina, 2015).

Schematic illustration of acid detergent fiber, neutral detergent fiber, and crude protein of annual ryegrass–cereal rye in Open and Tree pastures at the Horticulture and Agroforestry Research Center near New Franklin, MO.

       (adapted from Kallenbach et al., 2006).

      Enhancing beneficial insect populations

Schematic illustration of effect of trees on air and soil temperature of holm oak dehesas: (a) air temperature as a function of distance from the tree, and (b) soil temperature (ST) with respect to the air temperature both beneath and beyond the tree canopy.

       (adapted from Moreno Marcos et al., 2007).

      Improving Wildlife Habitat

      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