In situ and Ex situ Conservation of Commercial Tropical Trees - ITTO

492Populations of mycorrhizal fungi can be drastically affected by forest fire(eg. Amaranthus & Trappe 1993, Parke et al. 1984, Harvey et al. 1980, 1981).Since tropical rain forests often suffer from fire, there is a need to assessmycorrhizal fungal populations in an over-burned tropical rain forest.This paper reports a preliminary study to assess the effect of forest fireon the population of mycorrhizal fungi in a tropical rain forest in East Kalimantan,and discusses the importance of inoculating dipterocarp seedlings before plantingthem on over-burned forests.Literature ReviewMycorrhizaeMycorrhizae are mutualistic-symbiotic associations between fungi and roots ofvascular plants. The fungi benefit by the supply of carbon - particularlymonosaccharide sugars such as glucose and fructose – and other essentialsubstances such as vitamin B and certain amino acids from the hosts. Theplant, in return, gains fungal-absorbed nutrient elements, secondary metabolites,and soil moisture (Harley & Smith 1983, Kropp & Langlois 1990, Mukerji et al.1991).Smith and Read (1997) classified mycorrhiza into seven groups based onstructural characteristics and taxonomic classification of both fungal and plantsymbionts. However, only ectomycorrhizae and endomycorrhizae - or arbuscularmycorrhizae (AM) - are the most prevalent types of mycorrhizae in nature(Maronek et al. 1981).The ectomycorrhizal association is characterised by the presence of afungal sheath or mantle which develops to surround the root; a Hartig net,which is a network of hyphae growing intercellularly in the epidermal-corticalregion of the host root (Harley & Smith 1983, Wilcox 1982); and the presenceof hyphal systems connecting the ECM to both the soil and fruiting bodies ofthe fungi, forming the ECM (Harley & Smith 1983).The structure of the mantle, which covers the root, is highly variable (Warcup1990). It may vary from loose wefts of hyphae partially covering the root to adense pseudoparenchymatous sheath completely enclosing the root tip (Harley1969). The sheath thickness also varies, from 6 mm to 65 mm (Kope & Warcup1986). In the well-developed ECM, the mantle can constitute 20 - 40 percentof the total ectomycorrhizal root weight (Smith & Read 1997).The mantle sheath plays important roles in the enhancement of theabsorption surface of the host to allow increased water and nutrients, provisionof a physical barrier to soil-borne pathogens, and storage of beneficial substances