Arbuscular Mycorrhizas in Coastal Dunes

Abstract

Sand dune systems are among the best studied of primary successional sites and have attracted the attention of plant ecologists for over a century (Cowles 1899). Surprisingly, the traditional explanation of dune succession overlooks the critical contribution of mutualistic fungi that facilitate the invasion of barren areas. In fact, many of the dominant, dune-building plants appear to be incapable of growing in the dune environment if their roots are not associated with arbuscular mycorrhizal (AM) fungi, the topic of this chapter. The roots of dune species, like the vast majority of vascular plants, form symbiotic associations with fungi in the order Glomales (arbuscular mycor-rhizas). The fungal mycelia provide mineral nutrients in exchange for carbon compounds of the host plant (Smith and Read 1997). Arbuscular mycorrhizas were first reported in sand dunes in Pancraticum maritima, Convolvolus soldanella and Cineraria maritima in Italy (Stahl 1900). Since then,all the surveys of dunes throughout the world have shown that most of the plants distributed in embryo dunes and foredunes, mobile, semi-fixed and fixed dunes are heavily colonized by AM fungi ,e. Tadych and Blaszkowski 2000a). AM fungi are obligate symbionts, unable to complete their life cycle without a host plant (Smith and Read 1997). Less recognized is the fact that most plants grown under natural conditions (as opposed to greenhouse conditions with added fertilizer, water, and pesticides) cannot thrive without AM fungi (Trappe 1987). The AM association may be of considerable ecological significance for the establishment and growth of sand dune pioneer plants, because the fungi enhance plant nutrient uptake, particularly phosphorus (P), increase plant tolerance to drought and salt stress, and protect against soil Ecological Studies, Vol. 171 M.L. Martínez, N.P. Psuty (Eds.) Coastal Dunes, Ecology and Conservation