Читать книгу North American Agroforestry - Группа авторов - Страница 98

Many plant species show some degree of plasticity (the ability to respond to changes in local nutrient supplies or impervious soil layers) in their vertical (as well as lateral) root distribution (Kumar & Jose, 2018). Plants also exploit plasticity to avoid competition (Ong et al., 1996; Schroth, 1999). Belowground niche separation in response to competition can help component species in an agroforestry system to avoid competition. This can lead to complementary or facilitative interactions that help increase the production potential of the system.

It is possible to apply treatments such as repeated disking, knifing of fertilizer applications, or trenching, applied while trees are young, to force tree roots to grow deeper. Wanvestraut et al. (2004) observed pecan roots displaying plasticity by penetrating deeper soil strata, thereby avoiding a region of high cotton root density. This enhanced the overall water use efficiency of the system because the cotton plants were able to capitalize on the water available in the topsoil layer while the pecan trees exploited the moisture available in the deeper soil layers. Zamora et al. (2007) corroborated the findings of Wanvestraut et al. (2004) and confirmed the morphological plasticity of cotton roots in response to competition from pecan trees.

Dawson, Duff, Campbell, and Hirst (2001) demonstrated that cherry (Prunus avium L.) tree root distribution was influenced by grass competition in a silvopastoral system in Scotland. Cherry roots increased within the upper soil surface horizon after grass competition was removed with herbicides, and in areas where grass competition was not removed, the average depth of the tree roots increased with time.