Lianas can negatively affect their host tree.The evidence comes from studies in tropical forests where\r\nlianas decrease the growth rate and reproduction of their host tree. This is primarily a consequence of water and\r\nnutrient competition two limiting factors in tropical forests. In contrast for some areas of southern temperate\r\nrainforests the competition for these resources could be less severe because of the high rainfall and fertile soils.\r\nBut so far no study has determined the effect of liana competition over their host tree in southern temperate\r\nrainforests.The aim of this study was to evaluate in field conditions the effect of liana Cissus striata (Ruiz & Pavon)\r\ncompetition over the growth rate of mature Nothofagus obliqua (Bidr Egefam) host tree. In an experimental\r\napproach we determined whether above- and/or below-ground competition is more important in this interaction.\r\nWe also looked for compensatory strategies that would allow to trees to respond to liana competition. In field\r\nconditions we found that infested trees have a decrease in their relative growth rate of 26% and a reduction of the\r\nleaf area index (LAI) of 20% compared with control trees. In the greenhouse experiment we found that saplings\r\nwere water stressed and that there was light competition. Neither competition for water nor light had a significant\r\neffect on the growth rate of infested saplings. This could be explained because saplings showed compensatory\r\nstrategies in response to competition.These strategies were based in the biomass distribution between organs (leaf\r\narea slenderness index) and within leaves (LMA). In conclusion we found that C. striata has a negative effect over\r\nthe growth of mature and sapling N. obliqua host trees.This was a consequence of above-ground and below-ground\r\ncompetition but we cannot disentangle which type of competition is more important. Trees respond to liana\r\ncompetition mature host trees change the canopy architecture and saplings allocate resource between and within\r\norgans which allows them to optimize resource capture.