Landscape‐scale drivers of liana load across a Southeast Asian forest canopy differ to the Neotropics

Abstract

1. Lianas (woody vines) are a key component of tropical forests, known to reduce forest carbon storage and sequestration and to be increasing in abundance.Analysing how and why lianas are distributed in forest canopies at landscape scales will help us determine the mechanisms driving changes in lianas over time. This will improve our understanding of liana ecology and projections of tropical forest carbon storage now and into the future. Despite competing hypotheses on the mechanisms driving spatial patterning of lianas, few studies have integrated multiple tree-level biotic and abiotic factors in an analytical framework.None have done so in the Palaeotropics, which are biogeographically and evolutionarily distinct from the Neotropics, where most research on lianas has been conducted.2. We used an unoccupied aerial system (UAS; drone) to assess liana load in 50ha of Palaeotropical forest canopy in Southeast Asia. We obtained data on hypothesised drivers of liana spatial distribution in the forest canopy, including disturbance, tree characteristics, soil chemistry and topography, from the UAS, from airborne LiDAR and from ground surveys. We integrated these in a comprehensive analytical framework to extract variables at an individual-tree level and evaluated the relative strengths of the hypothesised drivers and their ability to predict liana distributions through boosted regression tree (BRT) modelling.3. Tree height and distance to canopy gaps were the two most important predictors of liana load, with relative contribution values in BRT models of 34.60%-45.39% and 7.93%-10.19%, respectively. Our results suggest that taller trees were less often and less heavily infested by lianas than shorter trees, opposite to

Light‐demanding tree species are more susceptible to lianas than shade‐tolerant tree species in a subtropical secondary forest

“…One possibility for the positive correlation between liana and light‐demanding tree abundance is that lianas may inhibit shade‐tolerant tree growth and survival, thus indirectly promoting the survival of light‐demanding trees (Schnitzer, 2018; Schnitzer et al, 2000). Alternatively, the correlation may also imply that lianas and trees share a similar regeneration niche, such as gaps, forest edges (Barry et al, 2015; Godoy‐Veiga et al, 2018; Grubb, 1977; Ledo & Schnitzer, 2014; Schnitzer & Carson, 2010; Waite et al, 2023), where resources are in high abundance, and that lianas and light‐demanding trees may eventually partition or compete for resources (Asner & Martin, 2012; Cai et al, 2009; Schnitzer & van der Heijden, 2019). In our relatively young and disturbed forests, light‐demanding trees and lianas generally grew in forest gaps, forest edges, or well‐illuminated areas; thus, light‐demanding tree species have a high possibility of sharing similar regeneration niches with lianas.…”