Forest ecosystems, mycorrhizae

For most of the world s plants mycorrhizae are the primary interface between physiologically active areas of the root and the external environment. Hence it is likely that many, perhaps most, allelochemical interactions Involving higher plant roots are mediated by the fungal symbiont. Herein we briefly review past research dealing with allelopathic effects on mycorrhizae, and discuss how interaction between mycorrhizae and chemicals may influence structural and functional aspects of ecosystems. Most studies to date have dealt with EM in forest ecosystems, and this is where our discussion will focus. 

Wallenda, T., Stober, C., Hogbom, L. et al. (2000). Nitrogen uptake processes in roots and mycorrhizas. In Carbon and Nitrogen Cycling in European Forest Ecosystems, Ecological Studies 142, ed. E. D. Schulze. Berlin Springer-Verlag, pp. 122-43. 

FOGEL R. 1980. Mycorrhizae and nutrient cycling in natural forest ecosystems. New Phytologist, , 199-212. 

Alexander, I. 1989- Mycorrhizas in tropical forests. In Mineral Nutrients in Tropical Forests and Savanna Ecosystems, ed. J. Proctor (Blackwell Scientific Publications, Oxford), pp. 169-188. 

Plant species differ widely in the extent of phosphorus absorption by their roots. Forest trees take up P from insoluble compounds with the help of mycorrhizas, whereas phosphorus is removed from soils by harvested crops ( 6 kg ha in agriculture), erosion and to a small extent by leaching (-0.1 kg ha ) and volatilization as phosphine PH3. In the case of erosion, colloids with their surface-bound P are transported into surface waters, and this leads to the eutrophication of aquatic ecosystems, for example in lakes. Leaching losses occur only in sand and peat soils, and in the case of organic phosphates. Under extreme redox situations - as in some paddy soils - phosphate is reduced to PH3 as a gaseous product. 

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