The effects of restoring logged tropical forests on avian phylogenetic and functional diversity

Abstract

Selective logging is the most prevalent land-use change in the tropics. Despite the resulting degradation of forest structure, selectively logged forests still harbor a substantial amount of biodiversity leading to suggestions that their protection is the next best alternative to conserving primary, old-growth forests. Restoring carbon stocks under Reducing Emissions from Deforestation and Forest Degradation (REDD+) schemes is a potential method for obtaining funding to protect logged forests, via enrichment planting and liberation cutting of vines. This study investigates the impacts of restoring logged forests in Borneo on avian phylogenetic diversity, the total evolutionary history shared across all species within a community, and on functional diversity, with important implications for the protection of evolutionarily unique species and the provision of many ecosystem services. Overall and understorey avifaunal communities were studied using point count and mist netting surveys, respectively. Restoration caused a significant loss in phylogenetic diversity and MPD (mean pairwise distance) leaving an overall bird community of less total evolutionary history and more closely related species compared to unlogged forests, while the understorey bird community had MNTD (mean nearest taxon distance) that returned toward the lower levels found in a primary forest, indicating more closely related species pairs. The overall bird community experienced a significant loss of functional strategies and species with more specialized traits in restored forests compared to that of unlogged forests, which led to functional clustering in the community. Restoration also led to a reduction in functional richness and thus niches occupied in the understorey bird community compared to unlogged forests. While there are additional benefits of restoration for forest regeneration, carbon sequestration, future timber harvests, and potentially reduced threat of forest conversion, this must be weighed against the apparent loss of phylogenetic and functional diversity from unlogged forest levels, making the biodiversity-friendliness of carbon sequestration schemes questionable under future REDD+ agreements. To reduce perverse biodiversity outcomes, it is important to focus restoration only on the most degraded areas or at reduced intensity where breaks between regimes are incorporated.

Effects of land‐use change on community diversity and composition are highly variable among functional groups

“…For example, declines in avian PD (Frishkoff et al. , Cosset and Edwards ) following land‐use change may indirectly disrupt seed dispersal or pollination services.…”

“…It would also suggest high potential for the disruption of the many fundamental ecological interactions that occur between taxonomic groups (e.g., predation, parasitism, pollination), with potential implications for ecosystem functionality. For example, declines in avian PD (Frishkoff et al 2014, Cosset andEdwards 2017) following land-use change may indirectly disrupt seed dispersal or pollination services.…”

Bird Functional Traits Respond to Forest Structure in Riparian Areas Undergoing Active Restoration

“…These species occur exclusively or preferentially in the forest interior, suggesting that their performance is directly related to tree size and density [4]. However, studies evaluating the responses of bird assemblages to forest restoration generally compare areas in restored vs remnant reference forests [28,29], classify areas in age classes [26,30], or use time since restoration as a continuous predictor variable [31,32]. Although these studies recognize the importance of vegetation structure on bird assemblages, few studies explicitly used the development of forest structure as a predictor variable.…”

“…For example, Santos-Júnior et al [28] found that the composition of bird functional groups in restored sites (<10 years) was similar to that of nearby small forest reference remnants but differed from that of a large forest reference site, likely due to greater environmental complexity and differential resource availability. Cosset and Edwards [29] found that the restoration of logged tropical forests had negative effects on both phylogenetic and functional diversity of birds due to the reduction of environmental complexity resulting from vegetation management. Intermediate stages of forest succession include birds from both open and forested sites, with dominance of generalist species [34].…”

“…Moreover, the recovery of taxonomic diversity does not necessarily imply in the recovery of important ecosystem functions, since taxonomic indicators consider all species as equivalent despite their differences in ecological traits [36]. The assessment of functional diversity and recovery of functional groups is fundamental to evaluate ecosystem restoration, since they provide direct links to ecosystem processes [29,37].…”