Forest gaps: a blessing in disguise? A review on gap dynamics, human interpolations and interventions

This review paper aims to highlight the variance between forest gap characteristics and gap-phase regeneration in natural and anthoropgenic-induced forest gaps. It also evaluates whether or not deforestation on natural tropical forest provides an opportunity for generating viable flora composition that would have better adaptability to the continually changing environment. By comparing the difference and a range of other aspects of the two disturbance regimes, it is evident that anthropogenic disturbances may pose an opportunity for good results in the gap-phase regeneration process, provided the extent and severity of induced disturbances mimic natural gap systems in term of damages initiated and size.Numerous literature have been able to differentiate and to some extent quantify the above terms and associate them discretely with the two disturbance regimes, but also considering that there is some overlaps in characteristics between them. It has been concluded in the review that natural gaps stand a better chance of recovering than anthropogenically induced gaps. However, the latter can do equally well if assisted by human ingenuity, but this is yet to be the case in a global sense

Structural recovery of logged forests in the Solomon Islands: implications for conservation and management

Much of the lowland tropical forests in the Solomon Islands have been heavily logged. However, little is known about the recovery status of these forests. We examined factors that influenced the recovery of forest structural attributes within 50 years after selective logging on Kolombangara Island in the western Solomon Islands. Twelve study sites—six logged and six unlogged—were identified across the Island, with two logged sites in each of three recovery-time classes: 10, 30, and 50 years after logging. Within each study site, 12 0.1-ha plots were randomly established, and a series of forest attributes measured in each plot. Our results revealed that local logging intensity and soil attributes have stronger influence on forest-structural recovery than do site attributes such as local topography or tree architecture. Furthermore, half a century of regeneration following logging is insufficient to permit full recovery of forest structure. We conclude that logged forests on Kolombangara and possibly across the Solomon Islands may not fully recover structurally before the next logging cycle, in the absence of a policy on re-entry harvesting. The development of such a policy coupled with robust forest-management measures is pivotal to facilitating sustainable logging while supporting biodiversity conservation in the Solomon Islands. This may be the last best hope for saving lowland forests and their biodiversity on this unique tropical archipelago

Dynamics of logging in Solomon Islands: the need for restoration and conservation alternatives

Forests of Asia-Pacific islands have undergone degradation by some of the worst-known selective logging practices in the tropics. It is unclear whether severely damaged forests can return to a pre-logging state via natural regeneration, or whether active restoration is required. In this review, we highlight how the socioeconomic dynamics in the Solomon Islands promote excessive logging, resulting in highly degraded forests. We detail seven key elements currently promoting excessive logging in this region: (i) economic interests, (ii) corruption, (iii) poor employment conditions in the logging sector, (iv) high forest accessibility, (v) resource limitations for forest monitoring, (vi) contention over logging benefits, and (vii) a paucity of information for policy development. Though research on the regeneration capacity of logged forests in the Solomon Islands remains extremely limited, we suggest that some logged forests in the country may require active restoration—especially those that have been most heavily damaged. Our argument is based on previous tree planting initiatives in logged forest in the 1970s and 1980s. We propose three broad restoration techniques—enrichment planting, direct seeding, and the use of artificial perches—as viable options to help restore logged forests in the Solomon Islands. Lastly, we recommend the conservation-concession model to aid forest restoration, given its recent success in the region

The PREDICTS database: a global database of how local terrestrial biodiversity responds to human impacts

Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species’ threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project – and avert – future declines. We describe and assess a new database of more than 1.6 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries. The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups – including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans. The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses. The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems – www.predicts.org.uk). We make site-level summary data available alongside this article. The full database will be publicly available in 2015

Regeneration and recovery dynamics of logged forests in the Solomon Islands

Logging is among the major drivers of deforestation and forest degradation in tropical landscapes globally. Its enduring persistence over the past century was driven by the high demand for tropical wood. Tropical forests in the Solomon Islands have been heavily logged over the last century, but very little is known about the recovery dynamics and ecology of logged forests in this region. Furthermore, it is still unknown whether these forests can return to a pre-cut state via natural regeneration processes. In this thesis, the effects of industrial selective logging on forest floristics, functions and structure are assessed in the Solomon Islands. Furthermore, factors influencing the recovery of these attributes and their implications in forest management and conservation are considered. This thesis initially assesses the rich plant biodiversity in Oceania, in Chapter 2. Results from this study suggest that highly varied landscapes in Papua New Guinea contain high plant endemism and beta diversity via intense segregation and establishment of locally varied vegetation communities. Therefore, to effectively conserve biodiversity in such forests, protection must include landscapes that best represent the full range of topographic and edaphic variability throughout the island to account for locally endemic species restricted to specific ecological niches. Chapter 3 reviews the differences between forest-gap characteristics and gap-phase regeneration in natural and anthropogenically created forest gaps in tropical forests. It also evaluates whether or not forest degradation can provide an opportunity for generating floral compositions in rainforests that might be better adapted to continually changing environmental conditions. A review of the dynamics of logging in the Solomon Islands in chapter 4 highlights how the socioeconomic dynamics in this small developing nation promoted excessive logging, resulting in highly degraded forests. The key elements discussed here are the roles of (i) economic interests, (ii) corruption, (iii) poor employment conditions in the logging sector, (iv) high forest accessibility, (v) resource limitations for forest monitoring, (vi) disputes over logging benefits, and (vii) a paucity of information for policy development. The review also suggests that some logged forests in the Solomon Islands may require active restoration—especially those that have been most heavily damaged. Chapter 5 compares the taxonomic diversity and composition of trees between unlogged forest and sites that were logged 10, 30 and 50 years previously to evaluate the floristic dynamics of these forests following timber harvesting. The results reveal that distance to logging roads and to unlogged forest influenced postlogging recovery, emphasising the importance of edge effects in influencing forest composition. At least in the first 50 years after logging, tree-community composition did not appear to converge over time toward that in unlogged forests. Although species assemblages in previously logged forests generally tend to shift over time from light demanding-pioneers to old-growth species, a long-lived pioneer Campnosperma brevipetiolata dominated the forest even 50 years after logging. It was suggested that the persistence of C. brevipetiolata may have hindered the recovery of tree communities in logged forests. The removal and harvesting of such persistent, long-lived pioneer trees via careful silviculture techniques could potentially help to accelerate recovery of heavily logged forests. Chapter 6 explores the influence of light on the occurrence of understory plant functional traits and diversity in logged forests. Plant functional types–growth form, chlorotype and leaf area were used to predict the development of post-logging understory plant communities as such functional types show strong links with disturbance history and capture interspecific variation in strategies that drive plant performance. The response of the plant-trait elements of each plant functional types to changing light levels was determined across post-logging recovery times of 10, 30 and 50 years. The highly varied associations between the influence of light and the occurrence of each plant-trait element across recovery times revealed in the results suggest that plant-trait elements are closely linked to a range of environmental response strategies. Functional diversity can fully recover to pre-cut levels if logged forests are given ample time to regenerate, suggesting that the functional diversity of forests in logged Oceanic forests can be highly resilient under effective management regimes. Factors influencing the recovery of tree biomass, wood density and understory tree-specific leaf area (SLA) in logged forests were investigated in Chapter 7. Harvest intensity, tree abundance and liana abundance influenced tree biomass and wood density, whereas elevation and ground litter affected understory tree SLA during post-logging recovery. Tree biomass and wood density did not recover to pre-cut levels after 50 years of post-logging regeneration whereas SLA values were similar among logged-forest time classes and unlogged forests. The full recovery of tree biomass and wood density within 50 years of logging is unlikely in the Solomon Islands. Improving the recovery of wood functional traits in logged forests in this region requires the development and implementation of policies that regulate initial harvest intensity and re-entry harvesting in post-logged forests. Chapter 8 examines factors that influenced the recovery of several forest 'keystone structures' during 50 years of post-logging regeneration in the rainforests of Kolombangara Island. The results reveal that half a century of post-logging regeneration has been insufficient for full structural recovery of logged forests on Kolombangara. The results also suggest that proxies of logging, soil and tree attributes were more important than topographical factors in influencing the recovery of keystone structures over time. Based on these results, it was concluded that logging practices in the Solomon Islands must be regulated by more rigorous and effective management policies in order to facilitate full structural recovery of forests. Finally, Chapter 9 presents a 'one–stop shop' for forest-restoration practitioners. This chapter discusses forest-restoration approaches that have been successfully implemented in tropical forests, and recommends an integrative approach whereby forest-restoration techniques are amalgamated for potentially better outcomes in heavily logged forests. Because of the high intensity of logging on Kolombangara, natural regeneration alone is inadequate to permit full recovery of forests to pre-cut levels within 50 years since logging. The findings presented in this thesis can be used for both precautionary and remedial approaches to manage logged forests in the Solomon Islands. Nevertheless, much more information is required in terms of research and policy development to ensure that these and other logged forests in Oceania are appropriately managed to balance important economic and conservation outcomes

Forest structure, plant diversity and local endemism in a highly varied New Guinea landscape

The Island of New Guinea is renowned for its high biodiversity, which arises in part from its complex geology and topographical variability. The island is, however, relatively understudied. We surveyed forest plant communities in the poorly studied Naoro-Brown catchment of the West Koiari region of Papua New Guinea. We identified four forest types—riverine successional forest, lower montane forest, hill forest, and riverine mixed forest—along a 13-km transect, and examined forest structure (tree height, stand density, and biomass) and tree species diversity (species richness, Shannon-Wiener diversity index, and composition) in these forest types. We also assessed the effect of local topography on floristic patterns. Forest structure and species diversity varied greatly among the forest types, with topography strongly affecting species assemblages. These results suggest that highly varied landscapes may contain high beta diversity via intense segregation and establishment of varied vegetation communities. Beta diversity in New Guinea may be higher than expected as such highly varied landscapes are common, yet poorly studied. To effectively conserve biodiversity in New Guinea's forests, protection must include forested landscapes that best represent the topographical variability throughout the island to account for locally endemic species restricted to specific ecological niches

Understory plant species and functional diversity in the degraded wet tropical forests of Kolombangara Island, Solomon Islands

Anthropogenic activities have resulted in extensive deforestation and forest degradation on many tropical oceanic islands. For instance, some islands in the Solomon archipelago have as little as 10% of primary forests remaining with few of these remnants protected from future land use change. We examine the plant species and functional diversity (excluding adult canopy trees) of 48 sites from four forest land use types (two types of primary forest, secondary forest and abandoned tree plantations) and two common human-maintained land use types (coconut plantations and grazed pastures) across three elevation bands on Kolombangara Island, Solomon Islands. In total, we surveyed 384 species from 86 families of which only 6.5% were non-native. Species richness was lowest in coconut plantations and grazed pastures and declined with increasing elevation across all land use types. Functional diversity was similar between primary and secondary forest (high richness, high evenness and unaltered dispersion) and lowest in coconut plantations and grazed pastures. Our results suggest that species and functional richness have had divergent responses to land use change in forest land uses indicative of a loss of functional redundancy. Despite structural and compositional similarities among primary forests and degraded forest land uses, full recovery of secondary and commercial plantations has not been achieved. We suggest that conservation of Kolombangara’s forest understory flora will require reserves across the island’s elevation gradient and may require active restoration in the future, particularly if degrading activities continue at the current rate

Factors influencing tree diversity and compositional change across logged forests in the Solomon Islands

Tropical forests in the Solomon Islands have been heavily logged in the last century. However, little is known about forest recovery dynamics across this region. Extrapolating findings from logged forests in tropical mainlands or large continental landbridge islands to isolated archipelagos such as the Solomons is inappropriate because succession and diversification patterns and processes differ between the former and latter. We compared the taxonomic diversity and composition of trees between unlogged forest and sites that were logged 10, 30 and 50 years previously to provide an indication of the potential dynamics of these forests following timber harvesting. The distance to logging roads and to unlogged forest influenced post-logging recovery, emphasising the importance of edge effects in previously logged forests. At least in the first 50 years after logging, tree-community composition did not appear to converge toward that in unlogged forests over time. Although species assemblages in logged forests generally tend to shift from light demanding-pioneers to old-growth species over time, a long-lived pioneer Campnosperma brevipetiolata dominated the forest even 50 years after logging. We suggest that recovery of the tree community in logged forests has been hindered by the persistence of C. brevipetiolata, and suggest that it could be thinned via careful silviculture techniques to enhance growth of mature-phase forest species. Removal of such persistent, long-lived pioneer trees could potentially help to accelerate recovery of heavily logged forests