Distances To Forest Edge Research Articles

Edge effects on ant diversity and functional composition in a forest fragment in the Central Amazon

The process of human-induced forest fragmentation increases the degree of isolation and causes biodiversity loss. Abrupt changes occur mainly near the edge of the fragment, where the average temperature is relatively higher and the humidity is lower. However, some natural environmental characteristics, such as higher air moisture in riparian areas, may buffer or minimize the edge effects. Here, we studied how the edge effect may affect ant species diversity and functional composition on valleys dissected by small streams (mesic areas). We categorized ant assemblages into the functional groups based on foraging, nesting habits, natural history information, and phylogeny. Ants were sampled using pitfalls and the Winkler extractor in ten riparian plots in a fragment of the Central Amazon. We individually fit the ant species richness, occurrence, and composition against two edge measures: forest edge distance and road-building distance. We recorded 99 species/morphospecies. Forest edge distance and road-building distance did not influence the occurrence and number of ant species per plot but were related to ant species composition. Moreover, there was not a clear pattern between functional groups distribution, except by leaf-cutters and generalist omnivorous species. Our results suggest a limited effect of forest edge distance and road-building distance on ant diversity

Edge effects of oil palm plantations on tropical anuran communities in Borneo

The expansion of industrial agriculture (oil palm) has significantly reduced lowland tropical diversity through direct loss or alteration of habitat, leading to habitat fragmentation and edge effects. Edge effects can have serious impacts on species diversity and community dynamics. To assess the effect of oil palm plantation edges on anuran communities in Sabah, Malaysian Borneo, we surveyed anuran species and measured structural habitat and landscape parameters at 74 sites spread across forest and plantation habitats along the Kinabatangan River. We then evaluated how anuran species richness and assemblage composition varied in relation to these environmental parameters. Relative species richness was higher at forest sites, compared to oil palm plantation sites. Plantation sites were dominated by wide-ranging terrestrial species, and assemblage composition varied mostly in relation to standing surface water. Forest habitats supported both more endemic and arboreal species. Variability on anuran assemblage composition in forest habitats was greatest in relation to distance to forest edge followed by canopy density, which was also partially correlated with forest edge distance. Moreover, anuran species richness in forest habitats declined as proximity to the forest-plantation interface increased, and as canopy density decreased. Our study provides further evidence that oil palm plantations provide little conservation benefit to anurans. Furthermore, oil palm plantations appear to have adverse pervasive impacts on amphibian diversity considerable distances into adjacent forest areas. These findings suggest that in order for small patches or narrow corridors of retained forest in landscapes managed for oil palm to maintain biodiversity values in the long term, their sizes and widths need to adequately account for the considerable influence of edge effects.

Are Scots pine forest edges particularly prone to drought-induced mortality?

Climate change is expected to exacerbate the frequency of drought-induced tree mortality world-wide. To better predict the associated change of species composition and forest dynamics on various scales and develop adequate adaptation strategies, more information on the mechanisms driving the often observed patchiness of tree die-back is needed. Although forest-edge effects may play an important role within the given context, only few corresponding studies exist. Here, we investigate the regional die-back of Scots pine in Franconia, Germany, after a hot and dry summer in 2015, thereby emphasizing possible differences in mortality between forest edge and interior. By means of dendroecological investigations and close-range remote sensing, we assess long-term growth performance and current tree vitality along five different forest-edge distance gradients. Our results clearly indicate a differing growth performance between edge and interior trees, associated with a higher vulnerability to drought, increased mortality rates, and lower tree vitality at the forest edge. Prior long-lasting growth decline of dead trees compared to live trees suggests depletion of carbon reserves in course of a long-term drought persisting since the 1990s to be the cause of regional Scots pine die-back. These findings highlight the forest edge as a potential focal point of forest management adaptation strategies in the context of drought-induced mortality.

Nest-site microhabitat association of red-billed leiothrix in subtropical fragmented forest in central China: evidence for a reverse edge effect on nest predation risk?

ABSTRACTPrevious studies of nest-site selection on a fine scale may reveal limiting resources within habitat types. The red-billed leiothrix (Leiothrix lutea Scopoli, 1786) is a common bird species that lives in the subtropical forests of Asia. Despite many reports of this species from introduced populations, little information has been obtained from its native range. From 2011 to 2013, we studied nest-site selection of red-billed leiothrix at micro-scales in Daweishan Nature Reserve, Hunan Province, central China. A total of 363 nests were found in five vegetation types. We measured the habitat variables and constructed nest-site selection models for nests found in the forest and scrub-grassland. Among the 18 variables measured in the forest, six variables were selected to construct the nest-site selection model: distance to forest edge (DTE), distance to water (DTW), vegetation comprehensive coverage, tree coverage, bamboo coverage and shrub height. According to Akaike’s information criterion, the best model consisted of five of these variables (excluding vegetation comprehensive coverage), and distance to forest edge, distance to water, tree coverage and bamboo coverage had negative effects on nest-site selection. In scrub-grassland, the DTE, DTW, and bush coverage (BUC) were selected from the 13 variables measured, and, accordingly, the best model consisted of DTE and BUC. Model averaging suggested that BUC had a positive effect on nest-site selection. In contrast, DTE has a reverse effect. In addition, DTE differed significantly between successful and failed nests in forest and scrub-grassland. More successful nests were found near the forest edge. Taken together, these findings emphasise the power of fine-scale habitat selection models in identifying relevant habitat variables with a significant effect on preferred habitat and eventually, breeding success.

Edge effect on epiphyllous bryophytes in Taita Hills fragmented afromontane forests

We investigated forest edge effects on the composition, abundance and species richness of epiphyllous (leaf-inhabiting) bryophytes in tropical cloud-forest fragments in the Taita Hills (Eastern Arc Mountains, Kenya). Six sample plots each of 0.04 ha (20 × 20 m) were established along a disturbance gradient extending in 200 m from the forest edge at three sites. Four leaves were collected from each phorophyte species and the diversity of epiphyllous bryophytes examined. Relative humidity and temperature readings were recorded using time-calibrated data loggers and a digital hygrometer. The epiphyllous species composition among localities and forest-edge distance classes were analysed using multivariate procedures. Overall, 1387 leaves distributed across 489 phorophytes were studied, and 95 species of bryophyte epiphylls were found in the 18 0.04-ha plots selected. The richness and distribution of epiphyllous bryophyte species did not change with the forest-edge distance, but rather depended on phorophyte species composition and (micro-) environmental variables such as sunlight exposure and spatial and dimensional canopy structure. The differences in epiphyll diversity among forest fragments were thus influenced by site-specific characteristics. Our findings suggest that management policies addressed to preserve ancient uncut stands that exhibit as much original phorophyte diversity as possible, need to be urgently achieved to protect epiphyll communities in African tropical cloud forests.

Forest regeneration dynamics following bark beetle outbreak in Norway spruce stands: Influence of meso-relief, forest edge distance and deer browsing

Management of Norway spruce monocultures in Europe is becoming increasingly difficult due to frequent natural disturbances. Their transformation could be especially challenging if several disturbances interact. In 2003 a spruce bark beetle outbreak damaged large tracts of spruce bottomland successional forest in southeast Slovenia where overabundant ungulate populations are present. In openings (5.4–7.5ha in size) in four salvaged forest compartments, we studied the effects of meso-relief, forest edge, seed trees and fencing on vegetation succession and tree regeneration. In 2005 and 2013 we sampled seedling density on 240 plots according to height class and species. In the second inventory we also assessed distance to seed trees and on a subsample of the plots the coverage of vascular plants. The results indicated sufficient natural regeneration and niche partitioning among species groups, with Norway spruce seedlings being more successful at stand edges, pioneers and anemochorous broadleaves in gap centres, and zoochorous broadleaves on plateaus as opposed to sinkholes. Seedling density of all anemochorous broadleaves was higher closer to seed trees. Spruce seedling abundance was negatively associated with the cover of herbaceous vegetation and that of pioneer trees with shrubs. Fencing resulted in significantly greater density, height and coverage of seedlings as well as a higher share of broadleaves. While bark beetle outbreak triggered regeneration of broadleaves, overbrowsing acted in the opposite direction by facilitating spruce. Thus, to accelerate successional development and to prevent a spruce dominated alternative ecosystem state, a significant reduction in deer abundance is needed. To safeguard seed sources, promote seed dispersal by encouraging perches and shelters, and preserve potential habitats, some damaged trees should be retained during salvaging operations.

Distribution of frogs in riparian areas of an urban forest fragment in Central Amazonia

This study aimed to evaluate how environmental variables (width of valley, stream size, forest edge distance, and leaf-litter depth) affect the abundance and richness of species of frog species in riparian areas of an urban forest fragment in Central Amazonia. The study was conducted at the campus of the Universidade Federal do Amazonas, Manaus, Brazil, between May 2008 and April 2009, when three nocturnal and diurnal samples were taken from ten plots. A total of 17 species belonging to seven families were registered. The number of species recorded per plot varied from seven to 14. We detected a relationship between the edge distance and richness: the plots with lower richness were located near the fragment border. The variables had no significant effect on abundance of each species.

Patterns of throughfall deposition along a transect in forest edges of silver birch and Corsican pine

In two adjacent forest stands in Flanders, one dominated by Corsican pine ( Pinus nigra subsp. laricio Maire) and another dominated by silver birch ( Betula pendula Roth), throughfall deposition was monitored along a transect perpendicular to the forest edge exposed to the prevailing wind direction. Throughfall deposition of Na+, K+, Ca2+, Mg2+, NH4+, NO3–, Cl–, and SO42–was examined on forest edge patterns expressed in the depth of influence of the edge effect (forest edge distance) and the level of enhancement at the edge (forest edge enhancement). In addition, an integrated forest edge enhancement factor was computed that incorporates these two parameters. Our results show that the edge effects on throughfall deposition of Na+, Cl–, the sum of so-called base cations, the sum of potentially acidifying ions, and the sum of inorganic nitrogen (NH4+ + NO3–) are more pronounced in the pine stand. The edge zone of the pine stand receives as a result of the edge effect 9.4 times more extra potentially acidifying ions and 12.7 times more extra inorganic nitrogen than the birch stand. We conclude that an appropriate design or conversion of the edge structure, from high-density Corsican pine plantations into lower density deciduous forests, can reduce the input of acidifying and eutrophying pollutants in the forest edge.