PLANT-SOIL INTERACTIONS - ECOLOGICAL ASPECTS AND EVOLUTIONARY IMPLICATIONS

Building on the concept of plants as ecosystem engineers, and on publi shed information on effects of particular plant species on soils, we r eview the evidence that such effects can provide a positive feedback t o such plants. Based on case studies involving dune formation by Marra m grass, N supply by N-2-fixing plants, depression of N availability b y ericaceous plants, 'islands of fertility' in deserts, mull- and mor- forming temperate forest trees, and formation of peatbogs, as well as similar other cases, we conclude that there is strong evidence for pla nt-soil feedbacks in a variety of ecosystems. We argue, moreover, that these feedbacks could have played a role in the evolution of the plan t species in question. These ideas are based mainly on correlative obs ervations, and need further testing.