Spatial variation in liana effects on host‐tree allometry and biomass in an intact tropical forest

Abstract

Lianas are increasing in abundance across the tropics, yet local spatial variation in their effects on host‐tree allometry and biomass, and the drivers of this variation within forests, remain poorly understood. Using field inventory, drone photogrammetry, and terrestrial laser scanning (TLS) across a 50‐ha plot on Barro Colorado Island, Panama, we quantified how liana load reshapes host‐tree allometry and upscaled these effects from local spatial scales to estimate stand‐level biomass impacts. Height analyses included 1989 trees (129 species), while a TLS subset of 184 trees (50 species) provided crown, branch, and volume metrics. Hosts with heavy liana load were ~ 10% shorter at 20 cm diameter at breast height (DBH), tapering to ~ 7% at 100 cm DBH. These trees also had ~ 36% smaller crowns, ~ 50% lower crown volumes, and fewer, shorter, and thicker branches, together leading to a ~ 14% reduction in tree‐level aboveground woody biomass. At local scales, biomass loss was driven more by the basal area and number of liana‐hosting trees than by liana biomass itself, indicating that carbon impacts depend more on which and how many trees are infested than on liana abundance alone. Lianas compensated only 43% of displaced tree biomass, leaving a net stand‐level carbon shortfall of ~ 4.6 Mg ha −1 relative to a liana‐free scenario. Using hierarchical models that account for spatial variation in liana pressure, we show that liana‐induced structural changes are spatially heterogeneous within intact tropical forests.