Methods for Ecological Studies of Mycorrhizae

Abstract Mycorrhizae are generally mutualistic associations in which plant hosts receive soil resources (mineral nutrients and water), while fungal endophytes receive photosynthetically derived carbon compounds (Harley 1989; Allen 1991). Mycorrhizae are inseparable components of soil ecosystems and are important in plant nutrition, nutrient cycling, food webs, and the development of soil structure. The mycorrhizal condition has evolved independently many times. Four distinct types of mycorrhizae are traditionally recognized: arbuscular mycorrhizae, ectomycorrhizae, orchid mycorrhizae, and mycorrhizae in the Ericales (Smith and Read 1997). These mycorrhizal types differ greatly in their plant and fungal associates, morphology, and ecological distributions (Tab. 18.1). Arbuscular mycorrhizae usually predominate in grasslands, agricultural systems, arid and semiarid biomes, certain temperate hardwood forests (including orchards), and many tropical forests (Brundrett 1991; Allen et al. 1995). Ectomycorrhizae tend to occur in forest trees and shrubs in areas where plant growth is seasonal or intermittent. Orchid mycorrhizae are most common in tropical systems where orchids are abundant and diverse. Ericales mycorrhizae are common in habitats suited for ericaceous plants, such as bogs and heathlands in temperate and boreal ecosystems.