Different patterns of biomass allocation of mature and sapling host tree in response to liana competition in the southern temperate rainforest

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