ROOT BIOMASS AND SYMBIOSES IN ACACIA-MANGIUM REPLACING TROPICAL FOREST AFTER LOGGING

Fine root biomass, A-mycorrhizal infection and root nodulation was stu died ia two watersheds planted with Acacia mangium, where one of the w atersheds (W5) had been subject to tractor logging and burning of resi dues after clearfelling, while the other (W4) had been subject to manu al hauling of timber and no burning. The latter treatment had proved m ore successful; growth of A. mangium was twice as high, while nutrient losses were reduced by 50%. In our study we could not directly attrib ute these differences to variations in fine root biomass or occurrence of root symbioses. However, on tractor tracks, which covered 24% of W 5, fine root biomass was reduced by 75%, and mycorrhizal infection and root nodulation were reduced as well (as compared to elsewhere in W5) . These negative aspects should be taken into account when logging ope rations are planned, in particular since effects of tractor tracks can persist for many years. (C) 1998 Elsevier Science B.V.