Temperature shapes liana diversity pattern along a latitudinal gradient in southern temperate rainforest

Abstract

The decrease in liana diversity with increasing latitude has been indicated as the major physiognomic difference between tropical and temperate forests’ ecosystem. Despite the robustness of this pattern, there is contrasting evidence about the environmental factors that model it. Here we evaluate the role of temperature, precipitation, soil fertility, and their interaction, over the richness and abundance pattern of liana species in a latitudinal gradient in the southern temperate rainforest. The study was carried out in the temperate rainforest of South America, in a latitudinal gradient from 37.4° S to 45.2° S encompassing 932 km. On this gradient, we select six study sites, with a total of 48 plots of 225 m² each. In each site, we recorded species richness and abundance of lianas, temperature, precipitation, and soil nutrition. We use lineal models and AIC models to evaluate the relation between diversity and environmental factors. Liana diversity strongly declines with increasing latitude on the southern temperate rainforest. This result is consequence of the latitudinal decrease in liana species richness, but not a decrease in their abundance over latitude. The decrease in species richness was correlated with the reduction in temperature (mean minimum temperature, absolute minimum temperature, and number of frost events), and with no other environmental factors (precipitation, seasonality, or soil fertility) or their interaction. Our results support the hypothesis that cold intolerance is the key factor shaping the global pattern of liana diversity.