Forest structure determines the abundance and distribution of large lianas in Gabon
Poulsen JR; Koerner SE; Miao Z; Medjibe VP; Banak LN
Global Ecology and Biogeography
Lianas are an important component of forest structure in the tropics accounting for up to 45% of total stems. Mounting evidence that tropical forests are undergoing structural changes with a growing abundance of lianas reducing forest carbon storage potential imparts a sense of urgency to study the drivers that control liana abundance and biomass particularly in Africa where data come from a few small-scale studies.\r\n\r\nLocation\r\nGabon Africa.\r\n\r\nMethods\r\nIn the first countrywide study of lianas we implemented the most ambitious large-scale forest inventory in tropical Africa to date quantifying the density basal area and biomass of large lianas (=10 cm in diameter) using a systematic random design of 104 plots located across Gabon. Additionally we examined the relative importance of environmental variables (mean annual precipitation mean annual temperature seasonality soil nitrogen soil fertility) disturbance (effect of gaps forest type) and forest structure (large tree biomass) in driving macroscale variation in the abundance of large lianas.\r\n\r\nResults\r\nIn total we surveyed 1354 large lianas and found the density basal area and biomass of large lianas in Gabon to be comparable to that in other tropical forests. The success of large lianas was positively related to soil N but most strongly correlated with forest structure particularly large tree biomass. The strength of the association between large lianas and large trees increased with tree size class.\r\n\r\nMain conclusions\r\nForest structure and the availability of large trees may be more important predictors of the abundance and distribution of large lianas in African tropical forests than environmental variables and disturbance. Changing environmental conditions are likely to have little direct effect on large lianas but climate change defaunation and land-use activities that diminish forest structure and reduce the number of large trees could have strong indirect effects on large lianas in Central African forests.