Allelopathic Exclusion of Understorey by a Few Multi-Purpose Trees

SUMMARY The floristic composition and biomass of the understorey was assessed in three 4-year old multi-purpose tree species. Compared to 29 species in the open, Leucaena leucocephala harboured only 5, Eucalyptus tereticornis 12, and Casuarina equisetifolia 18. The dry weight of the ground cover was also considerably restrained under the trees and the proportional reduction was comparatively less in C. equisetifolia. Suppression of ground vegetation is ascribed to allelopathic affects rather than to physical competition for light, water and nutrients. Of the three tree species, C. equisetifolia proved less injurious to the undergrowth. In contrast to the other trees the dominant species under L. leucocephala was L. leucocephala itself, indicating its lack of autotoxicity.