An examination of scale of assessment,logging and ENSO-induced fires on butterfly diversity in Borneo

The impact of disturbance on species diversity may be related to the spatial scales over which it occurs. Here I assess the impact of logging and ENSO (El Niño Southern Oscillation) -induced burning and forest isolation on the species richness (477 species out of more than 28,000 individuals) and community composition of butterflies and butterfly guilds using small (0.9 ha) plots nested within large (450 ha) landscapes. The landscapes were located in three habitat classes: (1) continuous, unburned forest; (2) unburned isolates surrounded by burned forest; and (3) burned forest. Plots with different logging histories were sampled within the two unburned habitat classes, allowing for independent assessment of the two disturbance factors (logging and burning). Disturbance within habitat classes (logging) had a very different impact on butterfly diversity than disturbance among habitat classes (due to ENSO-induced burning and isolation). Logging increased species richness, increased evenness, and lowered dominance. Among guilds based on larval food plants, the species richness of tree and herb specialists was higher in logged areas but their abundance was lower. Both generalist species richness and abundance was higher in logged areas. Among habitat classes, species richness was lower in burned forest and isolates than continuous forest but there was no overall difference in evenness or dominance. Among guilds, generalist species richness was significantly lower in burned forest and isolates than continuous forest. Generalist abundance was also very low in the isolates. There was no difference among disturbance classes in herb specialist species richness but abundance was significantly higher in the isolates and burned forest than in continuous forest. Tree specialist species richness was lower in burned forest than continuous forest but did not differ between continuous forest and isolates.The scale of assessment proved important in estimating the impact of disturbance on species richness. Within disturbance classes, the difference in species richness between primary and logged forest was more pronounced at the smaller spatial scale. Among disturbance classes, the difference in species richness between continuous forest and isolates or burned forest was more pronounced at the larger spatial scale. The lower levels of species richness in ENSO-affected areas and at the larger (landscape) spatial scale indicate that future severe ENSO events may prove one of the most serious threats to extant biodiversity.     

Changes in liana community structure and functional traits along a chronosequence of selective logging in a moist semi-deciduous forest in Ghana

ABSTRACT

Background: Lianas are an important component of tropical forests that respond to logging disturbance. Determining liana response to selective logging chronosequence is important for understanding long-term logging effects on lianas and tropical forests.

Aims: Our objective was to quantify the response of liana communities to selective logging chronosequence in a moist semi-deciduous forest in Ghana.

Methods: Liana community characteristics were determined in ten 40 m × 40 m plots randomly and homogenously distributed in each of four selectively logged forest stands that had been logged 2, 14, 40 and 68 years before the surveys and in an old-growth forest stand (ca. >200 years).

Results: Liana species composition differed significantly among the forest stands, as a function of logging time span, while species richness fluctuated along the chronosequence. The abundance of liana communities and of reproductive and climbing guilds was lower in the logged forests than in the old-growth forest. The ratio of liana abundance and basal area to those of trees was similar in the logged forests, but significantly lower than those in the old-growth forest.

Conclusions: Logging impacts on liana community structure and functional traits were largely evident, though no clear chronosequence trends were recorded, except for species composition.     

Butterfly Community Composition Across a Successional Gradient in a Human‐disturbed Afro‐tropical Rain Forest

Knowledge of the recovery of insect communities after forest disturbance in tropical Africa is very limited. Here, fruit‐feeding butterflies in a tropical rain forest at Kibale National Park, Uganda, were used as a model system to uncover how, and how fast, insect communities recover after forest disturbance. We trapped butterflies monthly along a successional gradient for one year. Traps were placed in intact primary forest compartments, heavily logged forest compartments with and without arboricide treatment approximately 43 years ago, and in conifer‐clearcut compartments, ranging from 9 to 19 years of age. The species richness, total abundance, diversity, dominance, and similarity of the community composition of butterflies in the eight compartments were compared with uni‐ and multivariate statistics. A total of 16,728 individuals representing 88 species were trapped during the study. Butterfly species richness, abundance, and diversity did not show an increasing trend along the successional gradient but species richness and abundance peaked at intermediate stages. There was monthly variation in species richness, abundance, diversity and composition. Butterfly community structure differed significantly among the eight successional stages and only a marginal directional change along the successional gradient emerged. The greatest number of indicator species and intact forest interior specialists were found in one of the primary forests. Our results show that forest disturbance has a long‐term impact on the recovery of butterfly species composition, emphasizing the value of intact primary forests for butterfly conservation.     

How forest edge-center transitions in the herb layer interact with beech dominance versus tree diversity

Aims Forest fragmentation and the associated augmentation of forest edge zones are increasing worldwide. Forest edges are characterized by altered plant species richness and community composition. As the tree layer and its species composition has been shown to influence herb layer composition, changes in tree species composition or richness may weaken or strengthen edge effects in forest ecosystems. We studied effects of the edge–center transition, tree species composition and their potential interaction on the understory vegetation in the Hainich National Park, Germany's largest connected deciduous forest, allowing to cover large edge–center transects.Methods We established 12 transects in an area of 75 km 2 of continuous forest, 6 beech-dominated and 6 in multispecies forest stands. Each transect reached from the forest edge up to 500 m into the forest interior. Vegetation relevés were conducted in regular, logarithmic distances along each transect.Important findings Herb species richness was influenced by an interaction of edge effects and tree diversity level. With increasing distance from the forest edge, herb species richness remained constant in multispecies forest stands but rapidly decreased in beech-dominated forest stands. Further, herb richness was higher in the interior of multispecies forest stands. Percent forest specialists increased and percent generalists decreased with distance from the edge and this contrasting pattern was much more pronounced in beech-dominated transects. By using structural equation modeling, we identified litter depth mediated by tree species composition as the most important driver of herb layer plant species richness.     

Does selective logging change ground‐dwelling beetle assemblages in a subtropical broad‐leafed forest of China?

Selective logging with natural regeneration is advocated as a near‐to‐nature strategy and has been implemented in many forested systems during the last decades. However, the efficiency of such practices for the maintenance of forest species are poorly understood. We compared the species richness, abundance and composition of ground‐dwelling beetles between selectively logged and unlogged forests to evaluate the possible effects of selective logging in a subtropical broad‐leafed forest in southeastern China. Using pitfall traps, beetles were sampled in two naturally regenerating stands after clearcuts (ca. 50 years old, stem‐exclusion stage: selectively logged 20 years ago) and two mature stands (> 80 years old, understory re‐initiation stage: selectively logged 50 years ago) during 2009 and 2010. Overall, selective logging had no significant effects on total beetle richness and abundance, but saproxylic species group and some abundant forest species significantly decreased in abundance in selectively logged plots compared with unlogged plots in mature stands. Beetle assemblages showed significant differences between selectively logged and unlogged plots in mature stands. Some environmental characteristics associated with selective logging (e.g., logging strategy, stand age, and cover of shrub and moss layers) were the most important variables explaining beetle assemblage structure. Our results conclude that selective logging has no significant impacts on overall richness and abundance of ground‐dwelling beetles. However, the negative effects of selective logging on saproxylic species group and some unlogged forest specialists highlight the need for large intact forested areas for sustaining the existence of forest specialist beetles.     

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

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 slow-growing 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’.     

Differential diameter-size effects of forest management on tree species richness and community structure: implications for conservation

In this paper we tested the hypothesis that logging effects in the adult tree community reverberate upon the regeneration contingent. We examined the differences on the tree community between forest reserves and 10 year-old logged areas in the Yucatan Peninsula. We used a paired design in three independent sites to estimate the effects of logging on tree species richness, diversity, composition and structure. Analyses were conducted differentiating individuals of four diameter-size classes: 1–5, 5–10, 10–25, and >25 cm DBH. We found out that there were differential effects by size. Species richness in the smaller and larger diameter-size classes was significantly lower in logged areas. Floristic composition was also different between logged and unlogged areas, with a trend towards more secondary forest associated species and less primary forest associated species in logged areas, and a higher density of species represented by a single individual in unlogged reserves. In terms of structure, trees DBH <10 cm, lianas, and re-sprouting stumps were more abundant in logged areas. Our findings suggest that 10 years after logging, harvested areas show alterations in structure, and potentially a reduction in species richness. We suggest that to make timber extraction and forest conservation compatible at this site, it is necessary to gain a better understanding of the ecology and regeneration requirements of the less abundant species, and to assess whether current logging practices might hinder their permanence in the study area.     

Macromoth community structure along a 95-year post-harvest chronosequence in managed forests of northwest Washington State (U.S.A.), with comparison to old growth forest communities

1. The effects of timber harvest in the moist coniferous forests of western North America are not well documented for ecologically important arthropods such as moths.
2. We assessed the response of macromoth community structure (abundance, sample size-corrected estimates of species richness and diversity, and overall community composition) to time since deforestation at 20 previously logged sites (1–95 years post-harvest), and compared the macromoth communities at these stands to four old growth stands.
3. As stand age increased following timber harvest, the number of macromoths captured in ultraviolet light traps increased and the relative abundance of dietary generalists declined, but sample size-corrected estimates of species richness and diversity did not vary. Macromoth community composition of the youngest stands (<10 years post-harvest) differed markedly from each other but converged soon thereafter.
4. Macromoth communities at old growth sites featured higher capture rates, lower dominance by dietary generalists, and higher sample size-corrected estimates of species richness and diversity than at previously logged sites. Community composition profiles for old growth sites differed from all previously logged sites, but the differences were subtle except in comparison to the youngest logged sites. None of the 188 species we sampled were old growth specialists.
5. Our results reveal dramatic initial impacts of deforestation on macromoth communities in moist coniferous forests of western North America. Such effects are largely reversed within two decades post-harvest but some effects persist for at least 95-years following logging.

     

Selection harvest in temperate deciduous forests: impact on herb layer richness and composition

Herb layer richness and composition of four forest types and three different management treatments were investigated in 16 deciduous forest stands of northern Germany. Specifically, we compared the species richness and composition occurring in mature forest stands that were single-tree and group selection harvested to those in unmanaged reference stands. Mean species richness of all herb layer species increased significantly with increasing harvest severity. When analyzing plant groups separately, it became obvious that this overall pattern was not consistent. While a negative relationship was detected between vernal herb richness and harvest severity, group selection harvest significantly increased species richness of summer herbaceous forest species and generalists. Woody species richness was not related to harvest severity. Community composition of the spring aspect was not significantly affected by selection harvest, whereas herb layer species composition in the summer aspect differed significantly among the three harvest treatments. A dominance of highly competitive shrub and generalist species was confined to some parts of the most intensively harvested stands. Overall, our results indicate that the herb layer community was not severely adversely affected by selection harvest at the intensities used in the studied stands. It is suggested that selection harvest systems may be feasible tools with which to conserve local forest vascular plant diversity and at the same time to meet the demand for timber products. However, information about forest history and the implementation of the selection harvest system are basic requirements when interpreting the results of studies on understorey response to selection harvest.     

Effects of Logging on the Diversity of Lianas in a Lowland Tropical Rain Forest in Hainan Island, South China

Lianas are an integral part of tropical forest ecosystems, which usually respond strongly to severe disturbances, such as logging. To compare the effect of different logging systems on the lianas diversity in tropical rain forest, we recorded all lianas and trees ≥1 cm dbh in two 40-year-old forest sites after clear cutting (CC) and selective cutting (SC) as well as in an old-growth (OG) lowland tropical rain forest on Hainan Island in south China. Results showed that OG contained fewer liana stems and lower species richness (stems: 261, richness: 42 in 1 ha) than CC (606, 52) and SC (727, 50). However, OG had the highest Fisher's α diversity index (17.3) and species richness per stem (0.184). Species composition and dbh class distribution of lianas varied significantly with different logging systems. The mean liana dbh in OG (22.1 cm) were higher than those in CC (7.0 cm) and SC (10.4 cm). Stem twining was the most frequent climbing mechanism represented in the forest, as shown by the greatest species richness, abundance, basal area, and host tree number with this mechanism. The percent of host tree stems ≥4 cm dbh hosting at least one liana individual in SC (39%) was higher than CC (23%) and OG (19.5%). Large host trees (dbh≥60 cm) were more likely to be infested by lianas in SC and OG. Our study demonstrated that logging disturbance could significantly change the composition and structure of liana communities in the lowland tropical rain forest of south China.
     

Effects of Selection Logging on Birds in Northern Belize1

We compared bird diversity and frequency in selection logged and unlogged forest to determine the effects of recent selection logging on avian biodiversity in a subtropical, moist evergreen forest. We used a combination of mist netting and fixed-radius point counts to assess bird communities in February and March 1993 in northwestern Belize. Vegetation structure and composition was similar in logged and unlogged forest. The 66 most common species occurred with statistically similar frequency in logged and unlogged forest although 13 species were two times more frequent in intact forest. Numbers of total bird species were similar between logging gaps and the logged forest matrix, and between the logged forest matrix and unlogged forests. A comparison of numbers of species in 26 guilds based on migration strategy, diet, foraging substrate, and height strata also showed them to be similar regardless of logging history. Our results differed from previous studies that reported lower bird species richness and abundance of individual species in logged tropical forests than in unlogged forest. The differences might be explained by the lower logging intensity and/or greater levels of natural disturbance in our study area compared to previous studies.     

Changes in tree and liana communities along a successional gradient in a tropical dry forest in south-eastern Brazil

We investigated changes in species composition and structure of tree and liana communities along a successional gradient in a seasonally dry tropical forest. There was a progressive increase in tree richness and all tree structural traits from early to late stages, as well as marked changes in tree species composition and dominance. This pattern is probably related to pasture management practices such as ploughing, which remove tree roots and preclude regeneration by resprouting. On the other hand, liana density decreased from intermediate to late stages, showing a negative correlation with tree density. The higher liana abundance in intermediate stage is probably due to a balanced availability of support and light availability, since these variables may show opposite trends during forest growth. Predicted succession models may represent extremes in a continuum of possible successional pathways strongly influenced by land use history, climate, soil type, and by the outcomes of tree–liana interactions.     

Responses of an avian community to rain forest degradation

Cumulative impacts of logging and road building in a previously undisturbed tract of tropical rain forest in French Guiana were assessed by random sampling of the bird community and 1-km² plot counts of diurnal raptors. Similar surveys were carried out during road construction and 15 years later within 5km of the road and were also compared with the undisturbed bird community of a nearby primary forest. The main disturbance was the change in forest structure brought about by logging and secondarily the road opening, the roadside second growth and the depletion of large vertebrates by hunting pressure. The responses of different bird guilds were highly divergent according to their natural habitat requirements, their diet and their vulnerability to hunting. They resulted in a moderate decrease in overall species richness and equitability. All species pooled, the abundance of 118 species was lowered, that of 45 species did not change appreciably and 89 were favored or even appeared. The guilds most affected were those with large body sizes, from terrestrial foragers to canopy frugivores, mostly by hunting, and the open understorey specialists, notably large insectivores and mixed flock members, because of changes in forest structure after logging. The guilds favored by logging and road opening were many of the hummingbirds, upper canopy frugivores and omnivores, and gap, edge or low secondary growth specialists. Recommendations to minimize the negative consequences of human exploitation in rain forests include reducing the width of deforested roadsides to no more than 10–15m on either side, implementing much more careful logging practices and strongly limiting hunting pressure in newly opened areas.     

Burning and logging differentially affect endemic vs. widely distributed butterfly species in Borneo

We assess the differential impact of logging and ENSO (El Niño Southern Oscillation)-induced disturbance on the relative butterfly abundance and species richness of range-restricted and widespread species within the island of Borneo. Relative abundance and species richness were assessed using rarefaction and species accumulation curves in unburned isolates surrounded by burned forest, the burned forest itself, and continuous forest unaffected by ENSO-induced disturbance in addition to logged and unlogged landscapes in unburned forest. The relative abundance of endemics was significantly higher in unlogged forest than logged forest and significantly higher in unburned forest than burned forest. Rarefied species richness of range categories was similar (Bornean endemics) or higher (other categories) in selectively logged than unlogged forest. In contrast, rarefied species richness of range-restricted species was highest in continuous forest, intermediate in unburned isolates, and lowest in burned forest. Only two individuals of a single Bornean endemic species were found in all the burned forest. Although species richness was higher in all range categories in continuous forest than in unburned isolates and in burned forest, the difference was most pronounced for range-restricted species. Logging and ENSO-induced fires thus have contrasting effects on range-restricted species. While both increase the relative abundance of widely distributed species at the expense of range-restricted species, only ENSO-induced disturbance lowers the rarefied number of restricted range species. Our research highlights the threat that severe ENSO events pose to geographically restricted classes of biodiversity.     

Disturbance, selective logging and bird diversity: a Neotropical forest study

The composition and structure of bird communities, and the damage to forest structure were surveyed in northern French Guiana (northeastern Amazonia) one year and ten years after selective logging and compared with the situation in a similar undisturbed primary forest. A point-count method was used in which 937 0.25ha sample plots were censused for 20 minutes each, and their vegetation structure was measured. On average, 38% of the forest undergrowth was destroyed, then invaded by dense regrowth, and up to 63% of the canopy was substantially opened as a result of selective logging. Hunting pressure also increased due to access roads opened for logging. Among the 256 species recorded, overall bird species richness and abundance were depressed by 27–34% in the logged areas compared to primary forest. The most vulnerable guilds, which decreased by 37–98% in abundance, were mature forest understorey species, especially terrestrial ones and mixed flocks of insectivores. Hummingbirds, small gaps, vine tangles and canopy species did not decrease, nor increase significantly after logging. Only species naturally associated with dense second growth, forest edges and large gaps actually increased. Habitat specialization was the major determinant of vulnerability to logging, and, to a lesser degree, size (large) and diet (insectivorous), but foraging behaviour and rarity had little effect. Bird sensitivity to changes in logged forest structure may involve physiological intolerance, reduced food categories, increased exposure to predators, too dense understorey for their specific foraging behaviour and/or avoidance of gaps. Suggested improvements of current forest management and logging techniques for the maintenance of a higher proportion of the original biodiversity include minimizing logging damages, long rotations (>50 years) between cuts, and keeping unlogged forest patches within logging concessions.     

Recovery of bird communities after selective logging and clear-cutting in Kibale National Park,Uganda

In the face of the continuing destruction of tropical rainforests, a major challenge is to understand the consequences of these habitat changes for biodiversity and the time scale at which biodiversity can recover after such disturbances. In this study, we assessed the patterns in communities of birds among forests of varying age consisting of clear-cuts of former coniferous plantations, selectively logged compartments and primary forests in Kibale National Park, Uganda. Birds were surveyed by 10-minute point counts at 174 randomly located points in nine forest areas during September–October 2011. A total of 2 688 birds representing 115 species were recorded. The species density, diversity and dominance of all birds, and dominance of forest specialists showed no differences between forest areas, whereas the species density and diversity of forest specialists differed significantly between forest areas. The composition of communities of all birds and of forest specialists varied significantly among the forest areas. Our results show that even after 19 and 43 years, respectively, communities of birds in clear-cuts of former coniferous plantations and selectively logged forests have not fully recovered from the disturbances of logging, highlighting the need to preserve primary forests for conservation of birds.     

Don’t miss the forest for the trees! Evidence for vertical differences in the response of plant diversity to disturbance in a tropical rain forest

Ecological studies in tropical rain forests traditionally focus on trees above a threshold diameter at breast height (dbh), since ignoring plant species of the other structural compartments is believed to be an acceptable tradeoff between exhaustiveness and effectiveness. However, the consequences of missing species below a threshold dbh value have been largely neglected so far. We evaluated whether the response of species diversity of ≥10-cm dbh trees was similar to the response of other structural ensembles (namely treelets, saplings, and terricolous herbs) in a lowland tropical rain forest, to three disturbance regimes: natural gap dynamics (control), and selective logging with and without additional thinning. We studied forest vegetation composition and diversity in a 20-yr replicated field experiment comprising nine 1 ha permanent plots established in a semi-deciduous rain forest of the Congo Basin and equally distributed among the three treatments. Once corrected by stem density, species richness was similar between logged (20 years since logging) and untouched old-growth forest stands with respect of trees, but higher with respect of treelets. As disturbance intensity increased, species richness increased within sapling layers but decreased within herb layers, while species spatial turnover (beta diversity) increased in both cases. Regarding the parameters of the partitioned rarefaction curves and relative abundance distribution curves, no correlation was found between trees and any of the other structural compartments. Whilst tree and treelet species composition was similar among treatments, the understories still reflected past disturbance intensity, with a strong response of the sapling and herb layers. These results show that ecological studies based solely on tree layers (dbh ≥ 10 cm) are misleading because their response to disturbance cannot be used as a surrogate for the response of other structural ensembles. Long-lasting effects of anthropogenic disturbance on the sapling bank and the herb layer may durably influence the long-term forest dynamics. Since overstory but not understory plant communities have recovered from human disturbances 20 years after silvicultural operations, African tropical rain forest ecosystems may not be as resilient to selective logging as previously thought.     

Functional composition and phenology of fruit-feeding butterflies in a fragmented landscape: variation of seasonality between habitat specialists

For butterflies, tolerance to the matrix may be an important criterion of habitat occurrence in fragmented landscapes. Here we examine the relative effects of habitat fragmentation and the surrounding agricultural matrix on the functional composition of fruit-feeding butterflies of the Atlantic rain forest in southeastern Brazil. Generalized linear models were used to detect the effects of landscape metrics on butterfly richness and abundance of the total assemblage and functional groups. Circular statistics were used to analyze the patterns of monthly abundance of the total assemblage and functional groups in the forest remnants and the surrounding matrices. In total, 650 butterflies representing 57 species were captured; species composition differed significantly between the forest fragments and the surrounding matrices. We recorded 22 forest specialists, 18 matrix specialists, 11 common species with matrix preference and six common species with forest preference. Forest connectivity favored the richness of forest specialists, while habitat fragmentation enhances the richness and abundance of matrix-tolerant species. Circular analysis revealed that forest specialists were more abundant in the rainy season while matrix-tolerant species proliferated in the dry season. Although maintaining connectivity of forest fragments may increase the mobility and dispersion of forest species, our results showed that landscape fragmentation modify butterfly assemblage by promoting an increase of matrix tolerant species with detriment of forest specialists.     

The avifauna 23 years after logging in Kibale National park, Uganda

The bird fauna of logged and unlogged forest in Kibale National Park, western Uganda were studied and comparisons made. Species diversity and richness were higher in the logged areas. A single species, the Yellow-whiskered Greenbul Andropadus latirostris dominated in the logged compartment. However, the majority of individual birds found in the logged forest were generalist or forest-edge species. Over 84% of the forest interior specialist species that occurred in primary forest had recolonized or persisted in the logged forest; however, there were seven out of 48 understorey forest specialists that had not done so. Although there was moderate species overlap between the two habitats, the logged forest compartment had not fully recovered from logging after 23 years.