Estimating Above-Ground Liana Biomass in Disturbed Australian Tropical Forests

Abstract

Lianas (woody vines) contribute substantially to tropical forest functioning, including carbon cycling, which makes accurate estimates of their biomass essential. Here, we aimed to quantify the contribution of lianas to biomass and stem density in disturbed Australian tropical forests. First, we destructively sampled lianas from the Wet Tropics World Heritage Area of northeast Queensland to develop an allometric equation to estimate liana above-ground biomass (AGB) from stem diameter. We then compared the accuracy of this equation for estimating liana AGB to previously published equations developed elsewhere. Using data from 17 vegetation plots (20 × 20 m) across the Cassowary Coast Region, we calculated liana contribution to biomass using our new equation. Based on RMSE and concordance correlation coefficient (CCC), our allometric equation performed better than those previously published (RMSE = 5.46, CCC = 0.94). Liana AGB estimates using our equation were lower than those based on previously published equations by at least 14%, suggesting that lianas have a lower AGB per unit stem diameter in our study region. Frequent cyclones and past logging may have led to numerous liana stems that are damaged, deformed, or stunted due to a lack of tall trees. We found that lianas contributed ~10% of woody biomass and 36.5% of woody stem density, which rose to 58% if climbing monocots were also included. When compared to liana studies conducted elsewhere, these forests are at the upper end of the range for documented liana densities worldwide. Our findings highlight the importance of developing regional allometric equations for estimating liana biomass. This work also underscores the need for continued measurement and monitoring of lianas to better understand how tropical forests respond to disturbance and global changes.