Avian Use of Habitat Configurations Created by Forest Cutting in Southeastern Wyoming

Urban forest fragmentation can highly influence pollinator-plant interactions in close contrasting habitats of a local herb, Ajuga decumbens (Labiatae)

Abstract. Sulistyawati E, Tihurua EF. 2019. Analysis of the condition of forest interior and edge in Mount Papandayan, West Java, Indonesia based on floristic composition and structural characteristics of tree community. Biodiversitas 20: 900-906. Forest fragmentation creates forest edges that possess different biotic characteristic in comparison to its interior. Those differences may include difference in vegetation structure and composition, and ecological processes in the ecosystem. This study aims to compare the condition between forest interior and forest edge in Mount Papandayan and provide assessment of the overall condition of the forest based on its floristic and structural characteristics. We conducted vegetation analysis of tree in which six plots, each of 0.1 ha, were established in the forest interior and forest edge. Based on the results, species richness and diversity of tree were higher in the forest interior than the forest edge. Based on the importance value index, the proportion of co-dominant species in forest edge sites were higher than in the forest interior sites. In addition, tree density, regeneration potential, total basal area, wood density average, and biomass were higher in the forest interior than in the forest edge. Overall, Mount Papandayan suffers moderate disturbance, which follows through the intermediate disturbance hypothesis and this can be seen from its relatively high diversity index of tree yet it has moderate wood density average.

Summary We tested the hypothesis that different life‐history stages of the same plant species show different responses to forest edge and interior environments. We investigated the effects of forest edges on growth, survival and density of seedlings, juveniles and adults of an endemic New Zealand mistletoe, Alepis flavida, over a 5‐year period. Rates of establishment and growth were significantly higher for seedlings in forest interior than on forest edges but both juveniles and adults grew significantly faster on forest edges. Mortality rates were greater for juveniles than for adults, but there was no significant difference between forest edge and interior. Densities of seedlings and the larger size class of juvenile plants were significantly greater in the forest interior than on forest edges, whereas densities of the larger size class of adults were significantly greater on edges. Changes in densities over 5 years showed that larger juveniles increased in density only in the forest interior, whereas larger adults increased in density only on forest edges. Thus, seedlings of A. flavida have strong advantages in the forest interior, whereas juveniles and adults grow faster on forest edges. This study emphasizes the need to examine multiple life‐history stages in studies of edge effects.

Habitat fragmentation has a marked impact on the functional composition of tropical forest tree assemblages, and such change is likely to cascade through other trophic levels. Here, we investigate how habitat fragmentation affects extrafloral nectary (EFN)‐bearing plants and ant functional groups known to attend EFNs in a fragmented landscape of the Atlantic Forest. Extrafloral nectary‐bearing trees were identified in 50 0.1‐ha plots located in forest fragments, edge and interior patches. Ants were surveyed in 30 1‐m2litter samples in each of 17 forest fragments and in forest interior. Extrafloral nectary‐bearing plants accounted for 19.9% of individuals and 10.5% of species and included both pioneer and shade‐tolerant species similarly rich in the three habitat types. However, shade‐tolerant individuals accounted for >80% of EFN‐bearing plants in forest interior, compared with 2% in forest edge and 29% in fragments. Forest edge and fragment plots had a third fewer EFN‐bearing individuals and species compared with forest interior. This appeared to have important implications for local ant communities as the density of EFN‐bearing trees was the most important variable explaining the species richness of arboreal dominant ants. Our results show that plant loser–winner replacements promoted by forest fragmentation can cascade through higher trophic levels, with implications for forest dynamics and biodiversity conservation.

Abstract: We evaluated the preferred home ranges of three saproxylic beetle taxa along transects from the open field into the forest interior, and from the forest floor up to the canopy. By means of trap sets on metal scaffolds, vertical and horizontal strata were sampled across two types of forest edges: soft‐edge ecotones with a gradual transition from the field into the forest and hard edges with an abrupt transition. The forest edges consisted of different strata such as herbaceous fringe, shrub belt, unmanaged forest and managed forest. The thermophilic buprestids were mainly caught in the open land (herbaceous fringe and agricultural land) and in the upper forest mantle. In general, the cerambycids were most abundant in the open land and the lower forest mantle, but a few species favoured the forest interior. The bark beetles (Scolytinae) were equally distributed in all habitats. These distribution patterns of the taxa were observed in terms of both species numbers and abundances. Each species with at least five collected specimens was assigned to one of the three habitat types: open land, forest mantle and forest interior. Of 74 ranked species, only 16% were prevalent in the forest interior and are thus considered to be true forest species. The other 84% of the species were attributed to open land or the forest mantle and are, therefore, forest edge species. Soft forest edges generally supported a higher species richness than hard edges, particularly as regards Cerambycidae and Scolytinae. In terms of Shannon diversity, soft edges tended to be more diverse in buprestids and cerambycids. Overall, the forest interior showed the least species richness and diversity. Therefore, for the conservation of saproxylic beetles, not only the amount and quality of dead wood is important, but also the presence and design of forest boundary structures.

Structural breakdown of specialized plant-herbivore interaction networks in tropical forest edges

Altered microbial communities and nitrogen availability in temperate forest edges

Landscapes composed of small rural properties may support highly heterogeneous habitat, because they often support distinct types of land uses adjacent to surrounding forest fragments. Many butterfly species may benefit from this kind of landscape, as very distinct microhabitats can be found in a very restricted spatial scale. To better understand how different microhabitats are related to fragmentation in rural landscapes the present study collected the butterfly fauna in 18 sampling point sites, representing distinct types of forest edges and forest interiors. Although closely located, these sites showed no spatial autocorrelation. Instead, a major distinction in species richness and composition was found among forest interior and edge habitats while no significant difference was found in species composition among distinct edge habitats. Therefore, the high segregation of butterfly assemblages found in a very restricted geographic scale suggests the presence of two different groups of butterflies that respond independently to forest fragmentation, the forest interior assemblages and forest edge assemblages. This distinction of butterfly assemblages related to forest interior and forest edges were already reported, but our results highlights that these differences are found mostly due to species turnover between those habitats. In other words, both microhabitat types present a high number of specialized species compared to a smaller fraction of generalist species that may occurs in both microhabitats. Althoug, in the case of Atlantic Forest the species of special conservation concern are those true specialized in forest interior habitats and not those specialized in forest edges, the present study corroborates the importance of sampling different microhabitats when studying fragmentation processes, both inside and outside of fragments. Although forest edges may present different kinds of habitat types, species present along border tend to be as heterogeneous as species present in different locations inside the forest. This information should be considered in sampling designs of biodiversity essays that focus on a more consistent representation of local diversity.

AimForests are highly fragmented across Western Europe, making forest edges important features in many agricultural landscapes. Forest edges are subject to strong abiotic gradients altering the forest environment and resulting in strong biotic gradients. This has the potential to change the forest's capacity to provide multiple ecosystem services such as nutrient cycling, carbon sequestration and natural pest control. Soil organisms play a key role in this perspective; however, these taxa are rarely considered in forest edge research.LocationA latitudinal gradient of 2,000 km across Western Europe.MethodsWe sampled six dominant taxa of litter‐dwelling macro‐arthropods (carabid beetles, spiders, harvestmen, centipedes, millipedes and woodlice) in forest edges and interiors of 192 forest fragments in 12 agricultural landscapes. We related their abundance and community composition to distance from the edge and the interaction with forest age, edge orientation and edge contrast (contrast between land use types at either side of the edge).ResultsThree out of six macro‐arthropod taxa have higher activity‐density in forest edges compared to forest interiors. The abundance patterns along forest edge‐to‐interior gradients interacted with forest age. Forest age and edge orientation also influenced within‐fragment compositional variation along the forest edge‐to‐interior gradient. Edge contrast influenced abundance gradients of generalist predators. In general, older forest fragments, south‐oriented edges and edges along structurally more continuous land use (lower contrast between forest and adjacent land use) resulted in stronger edge‐to‐interior gradients while recent forests, north‐oriented edges and sharp land use edges induced similarity between forest edge and interior along the forest edge‐to‐interior gradients in terms of species activity‐density and composition.Main conclusionsEdge effects on litter‐dwelling macro‐arthropods are anticipated to feedback on important ecosystem services such as nutrient cycling, carbon sequestration and natural pest control from small forest fragments.

Tree diversity is increasingly acknowledged as an important driver of insect herbivory. However, there is still a debate about the direction of associational effects that can range from associational resistance (i.e., less damage in mixed stands than in monocultures) to the opposite, associational susceptibility. Discrepancies among published studies may be due to the overlooked effect of spatially dependent processes such as tree location within forests. We addressed this issue by measuring crown defoliation and leaf damage made by different guilds of insect herbivores on oaks growing among conspecific versus heterospecific neighbors at forest edges versus interior, in two closed sites in SW France forests. Overall, oaks were significantly less defoliated among heterospecific neighbors (i.e., associational resistance), at both forest edge and interior. At the leaf level, guild diversity and leaf miner herbivory significantly increased with tree diversity regardless of oak location within stands. Other guilds showed no clear response to tree diversity or oak location. We showed that herbivore response to tree diversity varied among insect feeding guilds but not between forest edges and interior, with inconsistent patterns between sites. Importantly, we show that oaks were more defoliated in pure oak plots than in mixed plots at both edge and forest interior and that, on average, defoliation decreased with increasing tree diversity from one to seven species. We conclude that edge conditions could be interacting with tree diversity to regulate insect defoliation, but future investigations are needed to integrate them into the management of temperate forests, notably by better understanding the role of the landscape context.

When a forest is fragmented, this increases the amount of forest edge relative to the interior. Edge effects can lead to loss of animal and plant species and decreased plant biomass near forest edges. We examined the influence of an anthropogenic forest edge comprising cattle pasture, coconut plantations, and human settlement on the mantled howler (Alouatta palliata), white-faced capuchin (Cebus capucinus), Central American spider monkey (Ateles geoffroyi), and plant populations at La Suerte Biological Research Station (LSBRS), Costa Rica. We predicted that there would be lower monkey encounter rate, mean tree species richness, and diameter at breast height (DBH) in forest edge versus interior, and that monkeys would show species-specific responses to edge based on diet, body size, and canopy height preferences. Specifically, we predicted that howler monkeys would show positive or neutral edge effects due to their flexible folivorous diet, large body size, and preference for high canopy, capuchins would show positive edge effects due to their diverse diet, small body size, and preference for low to middle canopy, and spider monkeys would show negative edge effects due their reliance on ripe fruit, large body size, and preference for high upper canopy. We conducted population and vegetation surveys along edge and interior transects at LSBRS. Contrary to predictions, total monkey encounter rate did not vary between the forest edge and forest interior. Furthermore, all three species showed neutral edge effects with no significant differences in encounter rate between forest edge and interior. Interior transects had significantly higher mean tree species richness than edge transects, and interior trees had greater DBH than edge trees, although this difference was not significant. These results suggest that forest edges negatively impact plant populations at La Suerte but that the monkeys are able to withstand these differences in vegetation.

To examine the hypothesis that the soil microbial community in a nitrogen (N) limited forest responds to moderately elevated N deposition (< 10 kg ha−1 yr−1), correlations between N deposition and soil microbial properties were analyzed in a cool temperate forest surrounded by normally fertilized pasture grasslands in northern Japan. Three experimental plots were established in forest edges adjacent to the grasslands, and the other three plots were in forest interiors at least 700 m away from the grasslands. N deposition in each plot was measured from May to November 2018. In August 2018, we collected litter and surface soil samples from all plots to measure net N mineralization and nitrification rates as indicators of microbial activity, and microbial biomass and various gene abundances (i.e., bacterial 16S rRNA gene, fungal ITS region, and bacterial and archaeal amoA genes) as indicators of microbial abundance. N deposition in forest edges was 1.4-fold greater than that in forest interiors, whereas maximum N deposition was 3.7 kg ha−1. N deposition was significantly correlated with net N mineralization and nitrification rates and 16S rRNA and bacterial amoA gene abundances. Microbial community structures analyzed for bacterial 16S rRNA gene and fungal ITS region amplicons were different between litter and soil samples but were similar between the forest edge and interior, although this analysis was made only for single pair of the two plots in the forest edge and interior. N deposition was also correlated with the soil C/N ratio and nitrate and ammonium contents. Thus, it was suggested that some soil microbial activities and abundances in an N limited forest likely responded to moderately elevated N deposition. These findings provide primary information on soil microbial response to moderately elevated N deposition.

Knowledge on the distribution of mosquito communities over time and across human‐modified landscapes is important in determining the risk for vector‐borne disease. The diversity of mosquitoes along a rainy season and edge effects were evaluated in a riparian forest in the Cerrado biome, Southeastern Brazil. Mosquito communities were sampled with Shannon traps in three distinct habitats (forest interior, forest edge and pasture) throughout an entire rainy season, comprising five sampling months (December 2015 to April 2016). A total of 13 549 mosquitoes belonging to 54 species were sampled. Mosquito species richness and abundance were greater in February, which coincided with the middle of the rainy season and just after the months with greater rainfall. Mosquito species richness did not differ among habitats for any particular month. In February, month when 74% of individuals were recorded, mosquito abundance was lower in the pasture compared with the forest edge and interior, which did not differ statistically from each other. Four of the six most abundant mosquito species (which account for 93.5% of the sampled individuals) had more individuals collected in the forest edge, and 28 species were more abundant at the edge compared with 15 species in the forest interior. Months with high rainfall probably allowed the availability and maintenance of high‐water level in breeding sites leading to a further increase in mosquito populations. While the pasture did not seem to have the ideal abiotic conditions and/or resources (e.g. food and breeding sites) for mosquito species, edge effects appear to favour mosquito populations. Therefore, the risk of mosquito‐borne diseases is expected to be greater in the middle of the rain season at the riparian forest‐pasture edge, when and where a greater number of disease‐vectoring species are present.

Many studies have compared songbird nesting success between forest edge and interior, but few have addressed potential factors underlying variation in nest predation pressure in relation to edge. We examined the relative abundance and species richness of songbird nest predators and the abundance of Brown-headed Cowbirds (Molothrus ater) in forest edge and interior within a fragmented, agricultural landscape in central Missouri, USA. Avian predators and cowbirds were more abundant in forest edges. There were no differences in small- or medium-sized mammalian predator abundance between edge and interior. Almost twice as many snakes were captured in edge as in interior. Predator species richness was significantly higher in forest edge. Forest vegetation structure was very similar between edge and interior, suggesting that differences in predator abundance and species richness were not driven by variation in habitat structure. Nest predator distribution in relation to habitat edge may therefore depend on factors at larger spatial scales, such as landscape context. We suggest that in areas fragmented by agriculture, nest predator assemblages in forest edges may differ from those in forest interior. Edges may attract a greater number of predator species, and some nest predators may be more abundant near the edges of forest patches, although the trend does not apply across all predator taxa. Generalizations about nest predators and edges should thus be made with caution, and conservation plans should consider the composition of local nest predator assemblages in order to predict potential impacts on nesting birds in edge habitat.

Little is known about how climatic variability affects fragmented forests and their abrupt edges. We contrasted effects of the 1997 El Niño drought between fragmented and continuous forests in central Amazonia, using long-term data on tree mortality. For 23 permanent 1-ha plots, annualized mortality rates of trees ≥ 10 cm diameter at breast height (dbh) were compared among a ‘baseline’ interval of 5-17 y before the drought, a 12-16-month interval during the drought, and a 12-13-month interval after the drought, using repeated-measures ANOVA. We also examined the size distributions of dead trees for each interval. During the drought, average annual tree mortality rose significantly in both forest edges (from 2.44% to 2.93%) and interiors (from 1.13% to 1.91%), and the magnitude of this increase did not differ significantly between edges and interiors. After the drought, tree mortality declined in all plots, but most dramatically on edges. Mortality rates were more variable over time on edges than interiors, and there was no evidence of time lags in mortality. In forest interiors, the size distributions of trees that died did not differ significantly among the three intervals. On edges, however, relatively fewer small (10-15 cm dbh) and more medium-sized (20-30 cm dbh) trees died in the post-drought interval, compared to other intervals. Moreover, forest edges lost a significantly higher proportion of large (≥ 60 cm dbh) trees than did forest interiors. These results suggest that droughts have relatively complex effects on fragmented Amazonian forests. Drought effects in our forest fragments probably were reduced by prior floristic and structural changes near edges and by adjoining regrowth forest that partially buffered edge vegetation from desiccating conditions.