Ectomycorrhizal diversity effects on plant responses to mycorrhizal associations

One of the most challenging questions faced by ecologists is whether there is a general relationship between biological diversity and ecosystem function. As rates of species extinction appear to be increasing – and evidence has emerged of decreasing biodiversity in plant and microbial communities as a result of air and soil pollution, intensification of agriculture and forestry (Pimm et al. , 1995) – the importance of establishing whether biodiversity per se is important for ecosystem function has become a central issue in ecology. While the effects of higher plant species diversity on aboveground productivity has received considerable attention (Loreau & Hector, 2001), and there is evidence that arbuscular mycorrhizal (AM) diversity increases plant species diversity and productivity (van der Heijden et al. , 1998; Klironomos et al. , 2000) the role of ectomycorrhizal (ECM) diversity in ecosystem function, with one exception ( Jonsson et al. , 2001), has not been experimentally investigated. In this issue, Baxter & Dighton (2001) (pp. 139–149) report on a study designed specifically to answer the question ‘does ectomycorrhiza diversity affect plant growth and nutrient acquisition?’.