Selective logging in tropical forests decreases the robustness of liana–tree interaction networks to the loss of host tree species

Abstract

Selective logging is one of the major drivers of tropical forest degradation, causing important shifts in species composition. Whether such changes modify interactions between species and the networks in which they are embedded remain fundamental questions to assess the 'health' and ecosystem functionality of logged forests. We focus on interactions between lianas and their tree hosts within primary and selectively logged forests in the biodiversity hotspot of Malaysian Borneo. We found that lianas were more abundant, had higher species richness, and different species compositions in logged than in primary forests. Logged forests showed heavier liana loads disparately affecting slowgrowing tree species, which could exacerbate the loss of timber value and carbon storage already associated with logging. Moreover, simulation scenarios of host tree local species loss indicated that logging might decrease the robustness of liana-tree interaction networks if heavily infested trees (i.e. the most connected ones) were more likely to disappear. This effect is partially mitigated in the short term by the colonization of host trees by a greater diversity of liana species within logged forests, yet this might not compensate for the loss of preferred tree hosts in the long term. As a consequence, species interaction networks may show a lagged response to disturbance, which may trigger sudden collapses in species richness and ecosystem function in response to additional disturbances, representing a new type of 'extinction debt'.

Do fragment size and edge effects predict carbon stocks in trees and lianas in tropical forests?

“…4), because the composition of trees at edges has changed to one with more defences against lianas (e.g. fast growth in pioneer species) (van der Heijden & Phillips 2009;Magrach et al 2016). Both are plausible, but the fact that tree carbon stock was consistently low in forest edges strongly suggests that microclimatic variables at edges can affect trees independently of liana dominance.…”

Positive effects of liana cutting on seedlings are reduced during El Niño‐induced drought

“…This increase in liana abundance may enhance the negative impacts on tree demographic rates (i.e. reproduction, regeneration, growth and survival) in aseasonal and seasonal tropical forests alike (Magrach et al., ; Wright, Sun, Pickering, Fletcher, & Chen, ). Although the effect of lianas on forest dynamics has been studied in more seasonal tropical forests (Estrada‐Villegas & Schnitzer, ; Van der Heijden, Powers, & Schnitzer, ), empirical support for the effect of lianas on tree growth and survival remains limited in aseasonal forests of Southeast Asia, which are important biodiversity hotspots of both flora and fauna (Estrada‐Villegas & Schnitzer, ; Myers, Fonseca, Mittermeier, Fonseca, & Kent, ; Wright, Sun, et al., ).…”

“…after felling) for seedling, sapling and tree growth (Campanello et al., ; Estrada‐Villegas & Schnitzer, ; Grauel & Putz, ). However, empirical evidence supporting post‐felling liana cutting practices in Asia remains limited with most studies on lianas in tropical Asia focusing on liana community structure and diversity (Campbell & Newbery, ; DeWalt, Ickes, Nilus, Harms, & Burslem, ; Magrach et al., ; Putz & Chai, ) and pre‐felling cutting (Lussetti et al., ; Putz, ).…”

“…While lianas are a natural component of tropical forests, land-use change by humans and increases in the frequency and severity of drought are promoting liana abundance and biomass (DeWalt et al, 2010;Ingwell et al, 2010;Laurance et al, 2001;Magrach et al, 2016;Phillips et al, 2002;Schnitzer & Bongers, 2011). The interaction between these global change drivers may enhance the negative effects of lianas on tree establishment, growth and survival, which presents a developing issue for tropical forest conservation (Magrach et al, 2016;Reynolds, Payne, Sinun, Mosigil, & Walsh, 2011). If logging and drought increase liana abundance, then the negative effects of lianas on trees are potentially increasing in logged forests, threatening forest recovery.…”

“…In other tropical areas, seedling survival should be monitored to assess to what extent results from SE Asia are transferable. & Burslem, 2006;Magrach et al, 2016;Putz & Chai, 1987) and prefelling cutting (Lussetti et al, 2016;Putz, 1991).…”