Inhibitory effects of <i>Eucalyptus saligna</i> leaf litter on grassland species: physical versus chemical factors

<p><b><i>Background</i></b>: In Southern Brazil, large areas of grassland have been replaced by <i>Eucalyptus</i> plantations. Vegetation is scarce under plantations which may be associated with <i>Eucalyptus</i> releasing of allelochemicals.</p> <p><b><i>Aims</i></b>: To investigate effects of <i>Eucalyptus saligna</i> leaf litter on the colonisation and development of the ground layer by grassland species and if these effects were related to allelopathy.</p> <p><b><i>Methods</i></b>: We assessed the effects of <i>Eucalyptus</i> litter on the establishment of species of the native grassland community and on seeded test species (<i>Paspalum notatum</i> and <i>Lotus corniculatus –</i> introduced). We tested the impact of the addition of <i>E. saligna</i> leaf litter, artificial leaves (shading and mechanical impediment) and shading. We also tested the phytotoxicity of the soil from <i>E. saligna</i> plantations.</p> <p><b><i>Results</i></b>: Species richness, diversity, plant height, cover and biomass were lower in <i>E. saligna</i> 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 <i>E. saligna</i> leaves, artificial leaves and shading treatments than in the control. Allelochemicals did not accumulate in soil at phytotoxic levels.</p> <p><b><i>Conclusions</i></b>: <i>Eucalyptus saligna</i> 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.