Abstracts |
Agroforestry has great potentials for providing numerous environmental services, including, among others, soil conservation, land rehabilitation, ground water-table stabilization, erosion control, and phytoremediation of soils contaminated with heavy metals and other pollutants. Phytoremediation, one of those environmental services provided by agroforestry, is the use of plants to decontaminate polluted soils. Phytoremediation involves extraction of soil pollutants by roots and accumulation or transformation by plants, e.g., hyperaccumulators. Hyperaccumulators are plants that can tolerate metals and organic pollutants and extract them from contaminated soils and accumulate them at concentrations far exceeding what normally would be found in plant tissues. Agroforestry systems restore contaminated soils through the decontaminating effects of legumes, hyperaccumulators, and hydraulic lift (a major mechanism behind soil water redistribution between soil layers in agroforestry systems). Legume species that are used in tropical agroforestry for nitrogen fixation in soils most often have the ability to decontaminate polluted soils, as symbiotic associations between legumes and symbionts (mycorrhiza and Rhizobium spp.) and actinomycorrhizal plants (mycorrhiza and Frankia spp.) enhance phytobial remediation. Hyperaccumulators are used for soil decontamination in several agroforestry systems, including riparian buffer systems, tree-crop combinations, and short woody rotation crops. Research to increase understanding of the functions of agroforestry with regard to environmental services, and of the impact of these benefits to landscape health, is emerging. Society has not yet exploited the full potential of agroforestry. This chapter will focus on an under-exploited agroforestry benefit in the form of phytoremediation. |