Inhibitory effects of Eucalyptus saligna leaf litter on grassland species: physical versus chemical factors

Background: In Southern Brazil, large areas of grassland have been replaced by Eucalyptus plantations. Vegetation is scarce under plantations which may be associated with Eucalyptus releasing of allelochemicals.Aims: To investigate effects of Eucalyptus saligna leaf litter on the colonisation and development of the ground layer by grassland species and if these effects were related to allelopathy.Methods: We assessed the effects of Eucalyptus litter on the establishment of species of the native grassland community and on seeded test species (Paspalum notatum and Lotus corniculatus - introduced). We tested the impact of the addition of E. saligna leaf litter, artificial leaves (shading and mechanical impediment) and shading. We also tested the phytotoxicity of the soil from E. saligna plantations.Results: Species richness, diversity, plant height, cover and biomass were lower in E. saligna leaves and artificial leaves treatments than in the control (absence of litter). The test species showed lower biomass and higher mortality in treatment plots with E. saligna leaves, artificial leaves and shading treatments than in the control. Allelochemicals did not accumulate in soil at phytotoxic levels.Conclusions: Eucalyptus saligna leaf litter suppresses the establishment of grassland vegetation, but the effects are mainly physical. Field evaluations with appropriate controls should be more extensively used in allelopathy investigations.