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The Importance of Ectomycorrhizas for the Growth of Dipterocarps and the Efficacy of Ectomycorrhizal Inoculation Schemes

2010; Springer Nature; Linguagem: Inglês

10.1007/978-3-642-15196-5_1

2196-4831

Francis Q. Brearley,

Ecology and Vegetation Dynamics Studies

The Dipterocarpaceae, ecosystem dominants and source of forest products in South-east Asia, form ectomycorrhizas (EcMs). Important fungal families involved in this symbiosis are Amanitaceae, Boletaceae, Pisolithaceae, Russulaceae, Sclerodermataceae and Thelephoraceae. The presence of EcM fungi on the roots of dipterocarp seedlings has been shown to improve P nutrition most notably but also N, Ca and Mg nutrition and to improve access to organic forms of N. In addition, EcMs have been shown to improve seedling growth although mostly under nursery conditions. These results have led it to be suggested that seedlings should be inoculated prior to being out-planted in reforestation programmes. Current and recent inoculation schemes have focussed on the genera Pisolithus, Scleroderma and Tomentella. The most controlled method to inoculate seedlings is to apply a known amount of inoculum of an identified, aseptically cultured EcM fungal species. In situations where this has not been feasible, tabletted EcM inoculum has been applied. The simplest to inoculate seedlings is to use forest soil colonised with EcM hyphae, root fragments and spores; whilst this does not guarantee the most beneficial fungus will be dominant on the roots of the seedlings it will allow EcM formation of some kind. Before assuming that pre-inoculating seedlings will bring long-term benefits to seedlings planted in soils where EcM inoculum is already present, a number of questions need to be asked. First, does inoculation actually improve growth and survival of out-planted seedlings? If so, second, under what conditions and situations is inoculation of benefit? Finally, is colonised soil inoculum just as good as single species inoculum? However, in soils lacking inoculum (such as burnt peat swamp forest and ex agricultural land), inoculating seedlings is more likely to be of benefit to initial seedling growth and survival. Whilst EcMs have often been shown to be beneficial for seedling performance, the warning raised over 40 years ago that "mycorrhizal infection should not be taken as the 'cure of all ills' in the establishment of trees" still applies today.