Do Thinning and Burning Sites Revegetated after Bauxite Mining Improve Habitat for Terrestrial Vertebrates?

Thinning and burning forests established on revegetated mine pits in jarrah (Eucalyptus marginata) forests of south‐west Australia is being considered as a management option to accelerate succession in sites with excessive tree densities. To assess the impact of thinning and burning on reptiles and small mammals, we installed trapping grids in eight thinned and burned sites, each paired with untreated controls. Of the eight pairs, four were in rehabilitated sites (planted with nonlocal species) and four were in restored sites (seeded with local species). Thinning and burning had no significant impact on the small mammal community, although Cercatetus concinnus was more abundant in rehabilitated sites. In contrast, thinning and burning significantly increased reptile abundance and species richness, with two species (Morethia obscura and Menetia greyii) only recorded in thinned and burned sites. We concluded that thinning and burning was a successful management option in revegetated mine pits in jarrah forests, particularly because reptile communities created by thinning and burning were more similar to those in unmined forest. Although published studies for comparison are few, we expect thinning and burning to have generally positive effects on reptile communities in forest ecosystems where fire is an important disturbance agent. Our study emphasizes the importance of monitoring revegetated areas over time periods sufficient to detect deviations from desired successional trajectories, so that management options, such as thinning and burning, can be implemented if required.     

Long-Term Trends in Faunal Recolonization After Bauxite Mining in the Jarrah Forest of Southwestern Australia

Abstract Fauna serve a key role in many forest ecological processes. Despite this, few studies have considered long‐term faunal recolonization after mining and rehabilitation of forest ecosystems. In the jarrah forest of southwestern Australia, permanent fauna monitoring sites have been established in bauxite mined areas rehabilitated in 1990 and in a range of representative unmined forest control sites. At each site mammals, birds, reptiles, and ants were surveyed in 1992, 1995, and 1998. The aims of the monitoring were to develop a better understanding of faunal recolonization trends, to produce recommendations for promoting fauna return, and to consider which techniques and fauna groups are best suited for monitoring recolonization. The results showed that successional trends varied between fauna groups. Generalist foraging mammals recolonized rapidly, whereas small predators took longer. Feral mice were initially abundant and then declined. Birds gradually recolonized, and after 8 years bird communities were very similar to those in unmined forest sites. Reptile species took longer, and after 8 years numbers of species remained lower than in unmined forests. Species richness and diversity of ants in 8‐year‐old rehabilitation were comparable with those of unmined forest in some rehabilitated sites but were lower in others. The composition of ant communities was still different from that of unmined sites. Ant species that only use disturbed forest declined rapidly in abundance as rehabilitation aged. The results suggest that although the rates of faunal recolonization will vary, with time most or all mammal, bird, reptile, and ant species should inhabit rehabilitated bauxite mines. The densities of many are likely to be similar to those in unmined forest, but for others it is too early to know whether this will be the case. Techniques for promoting fauna return are discussed. This study demonstrates that no single fauna group is suitable for use as an overall “indicator” of faunal recolonization; different fauna species and groups reflect different aspects of faunal succession.     

Microhabitat Preference of Egernia napoleonis in Undisturbed Jarrah Forest,and Availability and Introduction of Microhabitats to Encourage Colonization of Restored Forest

An animal's microhabitat requirements can impact its ability to colonize restored areas, particularly species requiring slow developing microhabitats, such as logs and woody debris piles. Introduction of these microhabitats may be required to facilitate colonization by some species. Restored bauxite mine‐pits in the Jarrah (Eucalyptus marginata) forest of south‐western Australia contain introduced log piles at densities of 1 ha^?1. However, these have not facilitated colonization by Napoleon's skink (Egernia napoleonis), which rely on logs for habitat and are largely absent from restored sites. We radio‐tracked 12 skinks in unmined forest to determine their microhabitat preferences and examined differences in vegetation structure, and microhabitat and food availability, between restored and unmined forests to identify reasons for their absence. Restored and unmined forests differed in canopy, mid‐ and understory cover and ground substrates, which were all potential barriers to colonization. Food availability was similar between restored and unmined forest, thus not a barrier to colonization. Skinks primarily utilized long logs, large woody debris piles, and large trees; microhabitats that were scarce or absent in restored sites and, therefore, potential barriers to colonization. Using this information, we introduced small woody debris piles into restored sites in close proximity to unmined areas containing skinks to facilitate skink colonization. This showed early signs of success and suggested that the lack of logs and woody debris were barriers to colonization. However, further monitoring is required to accurately determine the long‐term value of woody debris piles in facilitating skink colonization.     

Forest edges have high conservation value for bird communities in mosaic landscapes

A major conservation challenge in mosaic landscapes is to understand how trait‐specific responses to habitat edges affect bird communities, including potential cascading effects on bird functions providing ecosystem services to forests, such as pest control. Here, we examined how bird species richness, abundance and community composition varied from interior forest habitats and their edges into adjacent open habitats, within a multi‐regional sampling scheme. We further analyzed variations in Conservation Value Index (CVI), Community Specialization Index (CSI) and functional traits across the forest‐edge‐open habitat gradient. Bird species richness, total abundance and CVI were significantly higher at forest edges while CSI peaked at interior open habitats, i.e., furthest from forest edge. In addition, there were important variations in trait‐ and species‐specific responses to forest edges among bird communities. Positive responses to forest edges were found for several forest bird species with unfavorable conservation status. These species were in general insectivores, understorey gleaners, cavity nesters and long‐distance migrants, all traits that displayed higher abundance at forest edges than in forest interiors or adjacent open habitats. Furthermore, consistently with predictions, negative edge effects were recorded in some forest specialist birds and in most open‐habitat birds, showing increasing densities from edges to interior habitats. We thus suggest that increasing landscape‐scale habitat complexity would be beneficial to declining species living in mosaic landscapes combining small woodlands and open habitats. Edge effects between forests and adjacent open habitats may also favor bird functional guilds providing valuable ecosystem services to forests in longstanding fragmented landscapes.     

Home Range Size and Micro‐habitat Density Requirements of Egernia napoleonis: Implications for Restored Jarrah Forest of South Western Australia

Compared to natural forests, coarse woody debris (CWD) is typically scarce in restored forests due to the long time it takes to develop naturally. In post‐mining restored forests in the Jarrah forest of south western Australia, CWD is returned at densities of one log pile per hectare. We tested the adequacy of these densities for meeting the micro‐habitat requirements of Napoleon's skink (Egernia napoleonis), a species rarely found within restored sites. Home range size and overlap, and micro‐habitat densities used by skinks, were measured by radio‐tracking 12 individuals in natural, unmined forest. Napoleon's skinks had small home ranges (0.08 ± 0.02 ha), based on 8 individuals with sufficient fixes. All skinks overlapped in home ranges, with average overlaps of 43.5 ± 8.6%. Ten of the 12 skinks shared micro‐habitats and 4 shared them simultaneously, which indicates some social tolerance. This will influence as to how many micro‐habitats are required. Micro‐habitats were used at high densities: logs at 49.2 ± 8.8 ha^?1 and woody debris piles at 12.4 ± 4.8 ha^?1. Based on these densities, it is recommended that CWD is returned to restored forests at densities of 60 ha^?1, which should provide sufficient micro‐habitats for multiple skinks. Due to the infeasibility of returning such CWD densities across large areas of restored forest, CWD could be preferentially returned as patches, large enough for numerous home ranges, adjacent to unmined forest, or as corridors between unmined forest. These recommendations for returning micro‐habitats should be tested for effectiveness in encouraging recolonization of restored forest by Napoleon's skink and other species.     

Convergence Between Dung Beetle Assemblages of a Post-Mining Vegetational Chronosequence and Unmined Dune Forest

Abstract In Maputaland, South Africa vegetative and microclimatic changes on mined dunes drive the composition of the dung beetle fauna toward convergence with that in natural dune forest on unmined dunes. We assessed the pattern of these changes using a 23‐year vegetational chronosequence on mined dunes, which passes from grassland (approximately 1 year) to open Acacia shrubland thicket to Acacia karroo‐dominated woodland (approximately 9 years). Across this sequence, which represents successional stages in the restoration of dune forest, there was a sequential trend toward convergence in dung beetle species composition in both the entire species complement and, particularly, in shade specialist species. However, species abundance patterns showed a trend toward convergence only in early chronosequence Acacia woodland, followed by a decline in similarity between dung beetle assemblages of older Acacia woodland and unmined natural forest. This trend toward divergence was common both to the entire species complement, which includes widespread taxa, and to species endemic to Maputaland or the east coast. These trends in similarity and dissimilarity between dung beetle assemblages closely parallel the greater physiognomic and microclimatic similarity between early Acacia woodland and natural forest and the relative dissimilarity of older Acacia woodland. In conclusion, although percentage similarities between dung beetle assemblages of approximately 12‐year woodland and natural forests were comparable with those between each natural forest stand, decline in similarity in older woodland stands suggests that lasting convergence in dung beetle species abundance will only be attained once the Acacia woodland is replaced by secondary natural forest.     

Viability of ecological processes in small Afromontane forest patches in South Africa

Abstract The conservation of biodiversity is dependent on protecting ecosystem‐level processes. We investigated the effects of fragment size and habitat edge on the relative functioning of three ecological processes – decomposition, predation and regeneration of trees – in small Afromontane forests in KwaZulu‐Natal, South Africa. Ten sampling stations were placed in each of four forest categories: the interior of three large indigenous forest fragments (100 m from the edge), the edges of these large fragments, 10 small indigenous fragments (<1 ha) and 10 small exotic woodlands (<0.5 ha). Fragment size and edge effects did not affect the abundance of the amphipod Talitriator africana, a litter decomposer, and overall dung beetle abundance and species richness significantly. Bird egg predation was marginally greater at large patch edges compared with the other forest categories, while seed predation did not differ among forest categories. Tree seedling assemblage composition did not differ significantly among large patch interiors and edges, and small indigenous fragments. Sapling and canopy assemblage composition each differed significantly among these three indigenous forest categories. Thus, while tree recruitment was not negatively affected by patch size or distance from the edge, conditions in small fragments and at edges appear to affect the composition of advanced tree regeneration. These ecological processes in Afromontane forests appear to be resilient to fragmentation effects. We speculate that this is because the organisms in these forests have evolved under fragmented conditions. Repeated extreme changes in climate and vegetation over the Pleistocene have acted as significant distribution and ecological extinction filters on these southern hemisphere forest biota, resulting in fauna and flora that are potentially resilient to contemporary fragmentation effects. We argue that because small patches and habitat edges appear to be ecologically viable they should be included in future conservation decisions.     

Predation on artificial avian nests is higher in forests bordering small anthropogenic openings

Habitat edges alter the diversity of avian communities and are often associated with higher rates of nest predation. However, most previous studies on habitat edges have been conducted along long linear corridors or at the transition between large field and forest patches in agricultural systems. Less is known about predation rates when the habitat edge is the result of a small interior forest opening. We assessed predation rates on artificial nests mimicking ground and shrub nesters in Northern Michigan forests perforated by small clearings used previously for oil and gas extraction. Nests were placed at varying distances from the edges of these clearings, and in similar spatial arrangements within unfragmented interior forest plots. Predation rates increased in forests near edges, but significant impacts were limited to shrub nests. Markings on predated clay eggs indicated that the type of predation also differed. Scratch marks were the most prevalent egg indentation, but eggs with poked holes were twice as common near the forest edge. The increase in the number of poked eggs suggests that a higher density of avian predators occurred in forests near an edge. Predation rates at forest edges did not vary by distance from the forest edge. Surveys of the avian community revealed differences between edge and interior forests: American Crows Corvus brachyrhynchos and Blue Jays Cyanocitta cristata, two species known to predate bird nests, were more common near edges. Our results suggest that small forest openings alter the avian community and may adversely impact reproductive output in some species. If the alteration of these processes results in population‐level impacts, small forest perforations should be avoided when possible and reforestation of abandoned well‐pads should be encouraged.     

Consequences of forest fragmentation in an understory plant community: extensive range expansion of native dwarf bamboo

Understory bamboo species are important and influential components of temperate forests in at least several parts of the world. Here we report a study testing the effect of forest fragmentation on the dynamics of the dwarf bamboo Sasa chartacea and on forest herb communities in the Tokachi plain of Hokkaido, Japan. We studied 16 forest fragments of different sizes and small plots established in these fragments to examine the relationship between the abundance of S. chartacea, landscape and environmental conditions, and forest herb communities. Sasa chartacea was more abundant near forest edges and in smaller fragments, suggesting that the species has expanded its local range and increased its abundance in response to forest fragmentation. Edge‐related changes in light and soil moisture might have facilitated this range expansion. The species richness of forest herbs was strongly negatively related to the density of S. chartacea. Because much larger variation in species richness was explained by S. chartacea density than distance to the nearest forest edge, the expansion of S. chartacea has likely excluded other understory species by competition. In addition, the density of S. chartacea significantly explained variation in the species composition of forest herbs across plots. Taken together, our results emphasize the key roles of dwarf bamboos in changing plant communities following forest fragmentation.     

Reptile and Amphibian Responses to Restoration of Fire‐Maintained Pine Woodlands

Fire‐maintained woodlands and savannas are important ecosystems for vertebrates in many regions of the world. These ecosystems are being restored by forest managers, but little information exists on herpetofaunal responses to this restoration in areas dominated by shortleaf pine (Pinus echinata). We compared habitat characteristics and herpetofaunal communities in restored pine woodlands to relatively unmanaged, second‐growth forests in the Ouachita Mountains of western Arkansas, USA. We found woodland restoration with periodic burning affected species differently; some species benefited, some species appeared negatively affected, but most species did not respond clearly either way. Overall reptile captures were significantly (p = 0.041) greater in pine‐woodlands than in unrestored forest; one species of snake and three species of lizards were captured more often in woodlands than unrestored forests. Among anurans, we found no significant difference in captures between woodlands and unrestored forests for any species. Among salamanders, we captured western slimy salamanders (Plethodon albagula) almost exclusively in unrestored forest, but captures of other species did not differ between the two treatments. Historically, the Ouachita region likely consisted of a mosaic that included both fire‐maintained habitats (woodlands, savannas, and prairies) and areas of denser forest on mesic sites that were less likely to burn. Consequently, landscapes that retain both open woodlands and denser, less‐intensely burned forest (in the form of unharvested greenbelts or separate stands) would likely promote and maintain a greater diversity of herpetofauna.     

Edge-related changes in tree communities in the understory of mesic temperate forest fragments of northern Japan

We have assessed the effects of habitat fragmentation on understory tree communities in mesic temperate forests of the Tokachi plain of northern Japan. Tree community composition was analyzed across 13 forest fragments of various sizes ranging from 0.30 to 8.51 ha. The community composition varied along the edge-to-interior gradient: there was a lower abundance of shade-tolerant shrubs in forest edges than in forest interiors, while saplings of dominant canopy trees and pioneer trees were more abundant near the edges. The edge influence extended approximately 56 m into the forest interiors. Even the interior area of small fragments were likely to be affected not only by the nearest edge but also by more distant edges. Consequently, most areas in fragments smaller than 2 ha were covered by these “edge-type” communities. These results indicate that it is of primary importance to conserve and restore forests with an area at least larger than several hectares to sustain forest-interior tree communities.     

Edge effects on palm diversity in rain forest fragments in western Ecuador

At the edges of tropical rain forest fragments, altered abiotic and biotic conditions influence the structure and dynamics of plant communities. In Neotropical rain forests, palms (Arecaceae) are important floristic and ecological elements. Palms’ responses to edge effects appear to be idiosyncratic and to depend on the level of disturbance at edges. This paper explores how variation in forest structure at the edges of two old-growth forest fragments in a tropical rain forest in western Ecuador affects palms of different species, life-forms, and size classes. We investigate (1) how edge effects influence the relative proportion of palm adults and juveniles, (2) how distance from the forest edge affects palm density and species richness, (3) how altered forest structure along edges affects palm density. We found that at edges (1) palm communities had a lower proportion of adults relative to juvenile individuals compared to continuous forests, (2) the density of two species of palms and the overall species richness of the palm community tended to decrease toward the edges within forest fragments, and, (3) altered forest structure decreased the density of adult palms. Hence, edge effects on palms were controlled by the degree of modification of the forest structure, and by species responses to edge-related disturbance.     

Road edge effect on the abundance of the lizard <Emphasis Type="Italic">Gallotia galloti</Emphasis> (Sauria: Lacertidae) in two Canary Islands forests

Transportation infrastructure is a main cause of environmental change in forest landscapes worldwide. In the Canary Islands, a dense road system fragment the native Canarian pine and laurel forests causing potential changes in population densities of endemic lacertid lizards (genus Gallotia). Our aim was to assess road edge effects on relative abundance patterns of the endemic Gallotia galloti in both forests. We also explored the species–habitat relationships in this road-fragmentation context. We found that lizard relative density in relation to road edges differed between forests. Lizards were more abundant along edges and leeward interior, but virtually absent from the interior of the windward laurel forest. In the pine forest, lizards were present at three distances from edge, with a net decrease in abundance from edge to interior. These patterns may be explained partly by differences in vegetation structure regarding road proximity in each forest that potentially affect the helio- and thigmothermic character of G. galloti, and thus its habitat use. A general suggestion of this study is that road margins create corridors that may be used by native lizards for dispersal through inhospitable forest matrix. The high road density in Tenerife may have negative implications for the conservation of the genetic variability of G. galloti. At the island scale, increased communication between lizard populations through road corridors might increase homogenization of the gene pool. Ecological processes in which this lizard plays important roles may also experience changes along road edges.     

Edge disturbance drives liana abundance increase and alteration of liana–host tree interactions in tropical forest fragments

Closed‐canopy forests are being rapidly fragmented across much of the tropical world. Determining the impacts of fragmentation on ecological processes enables better forest management and improves species‐conservation outcomes. Lianas are an integral part of tropical forests but can have detrimental and potentially complex interactions with their host trees. These effects can include reduced tree growth and fecundity, elevated tree mortality, alterations in tree‐species composition, degradation of forest succession, and a substantial decline in forest carbon storage. We examined the individual impacts of fragmentation and edge effects (0–100‐m transect from edge to forest interior) on the liana community and liana–host tree interactions in rainforests of the Atherton Tableland in north Queensland, Australia. We compared the liana and tree community, the traits of liana‐infested trees, and determinants of the rates of tree infestation within five forest fragments (23–58 ha in area) and five nearby intact‐forest sites. Fragmented forests experienced considerable disturbance‐induced degradation at their edges, resulting in a significant increase in liana abundance. This effect penetrated to significantly greater depths in forest fragments than in intact forests. The composition of the liana community in terms of climbing guilds was significantly different between fragmented and intact forests, likely because forest edges had more small‐sized trees favoring particular liana guilds which preferentially use these for climbing trellises. Sites that had higher liana abundances also exhibited higher infestation rates of trees, as did sites with the largest lianas. However, large lianas were associated with low‐disturbance forest sites. Our study shows that edge disturbance of forest fragments significantly altered the abundance and community composition of lianas and their ecological relationships with trees, with liana impacts on trees being elevated in fragments relative to intact forests. Consequently, effective control of lianas in forest fragments requires management practices which directly focus on minimizing forest edge disturbance.     

Natural vegetation cover in the landscape and edge effects: differential responses of insect orders in a fragmented forest

Human activities have led to global simplification of ecosystems, among which Neotropical dry forests are some of the most threatened. Habitat loss as well as edge effects may affect insect communities. Here, we analyzed insects sampled with pan traps in 9 landscapes (at 5 scales, in 100–500 m diameter circles) comprising cultivated fields and Chaco Serrano forests, at overall community and taxonomic order level. In total 7043 specimens and 456 species of hexapods were captured, with abundance and richness being directly related to forest cover at 500 m and higher at edges in comparison with forest interior. Community composition also varied with forest cover and edge/interior location. Different responses were detected among the 8 dominant orders. Collembola, Hemiptera, and Orthoptera richness and/or abundance were positively related to forest cover at the larger scale, while Thysanoptera abundance increased with forest cover only at the edge. Hymenoptera abundance and richness were negatively related to forest cover at 100 m. Coleoptera, Diptera, and Hymenoptera were more diverse and abundant at the forest edge. The generally negative influence of forest loss on insect communities could have functional consequences for both natural and cultivated systems, and highlights the relevance of forest conservation. Higher diversity at the edges could result from the simultaneous presence of forest and matrix species, although “resource mapping” might be involved for orders that were richer and more abundant at edges. Adjacent crops could benefit from forest proximity since natural enemies and pollinators are well represented in the orders showing positive edge effects.     

Edge effects on epiphytic communities in a Mediterranean Quercus pyrenaica forest

Question: What are the edge effect responses of epiphytic lichen communities in Mediterranean Quercus pyrenaica forest? Location: Central Spain. Methods: We established ten transects perpendicular to a road dissecting a well conserved remnant of Q. pyrenaica forest into two sections. Transects extended from the forest/road edge to 100 m into the forest. Data were collected from seven plots in each transect at different distances from the edge. Variables were grouped into stand scale variables (distance to edge, number of trees per plot, mean diameter per plot, irradiance) and tree scale variables (diameter and height of sampled trees, aspect of the sampled square and relative height of the square). We used General Mixed Linear Models and constrained ordination techniques to test the hypothesis that the spatio‐temporal heterogeneity of light and water controls the occurrence of lichens and bryophytes along the edge‐interior gradient in the Q. pyrenaica forest. Results: Microclimatic parameters vary in a non‐linear way; edge and interior stands showed the most divergent and extreme values. Although the micro‐environment within Mediterranean forests is heterogeneous, interior conditions are apparently suitable for the performance of some specific forest epiphytes. Consequently, species richness does not show significant differences along the gradient. Total epiphytic cover increases towards the forest interior, but distance to the edge together with other predictors at the tree scale (aspect and height of the square) are the most relevant predictors for the composition and structure of these communities. Conclusions: Composition and structure of epiphytic communities in a Mediterranean semi‐deciduous forest are affected by the edge between the forest and the road constructed. Since some extremely rare lichens only occur at interior stands, the conservation of these threatened elements requires urgent conservation measures because well preserved and unmanaged forests in the Mediterranean region are very rare.     

Distributions of lizard species across edges delimiting open‐forest and sand‐mined areas

Abstract The distributions of lizards across habitat edges delimiting open‐forest and regenerating sand‐mined areas as a function of distance from the edge were studied at Tomago, New South Wales, Australia. Pitfall‐trapping was used to survey lizards across the northern edges of four forest fragments, to determine if lizards displayed characteristic responses across the edge, and whether these could be explained by the different habitat conditions. At each site, 11 equally spaced drift fences (each parallel to the edge) were arranged in a transect running perpendicular to the edge, and stretching 50 m into each habitat type. Captures of Amphibolurus muricatus (Agamidae) decreased substantially across the edge from the mine‐path to the forest so that it was identified as a mine‐path specialist lizard species. Captures of two skink species decreased across the mine‐path before reaching the edge, and were not caught (Ctenotus taeniolatus) or were seldom caught (Ctenotus robustus) in the forest, so they were identified as mine‐path specialist, edge avoiding, lizard species. Captures of Lampropholis delicata (Scincidae) increased across edges into the forest, consistent with the expectation for a forest specialist. Regression analyses indicated the responses to edges of three lizard species (A. muricatus, C. robustus and C. taeniolatus) were negatively correlated with canopy cover (probably due to its influence on temperature, as captures of A. muricatus and C. robustus were also correlated positively with mean daily temperature). In addition, the response of C. robustus correlated negatively with a vegetation factor (dense, even vegetation in the first 50 cm from ground level). The response of L. delicata correlated positively with understorey height. We have identified edge response strategies for four species of lizards across edges delimiting temperate open‐forest and mined areas, and identified habitat and microclimate variables that may have driven these responses.     

Seed rain across fire-created edges in a neotropical rainforest

Human-induced wildfires are increasing in frequency in tropical forests, and their deleterious consequences for biodiversity include decreases in seed rain, which may be affected directly by fire or indirectly by the creation of edges between forest and non-forest environments. Understanding seed rain is key to assess the potential for natural regeneration in plant communities. We assessed the impact of fire and fire-created edges on seed rain species richness, abundance, size, weight, and dispersal syndromes in Atlantic Forest remnants in Bahia, Brazil. We assessed seed rain at monthly intervals for an entire year along seven 300 m-long transects placed perpendicular to the edge. We installed seed traps at the edge and at 20, 40, 60, 80, 100, and 150 m into the burnt area and into the forest from forest edge. We recorded a total of 9050 seeds belonging to 250 morphospecies. We did not observe edge influence; however, we detected a lower abundance and proportion of animal-dispersed seeds in the burnt than in the unburnt areas. The seed abundance in the burnt areas was lower and seeds were smaller and lighter than those in the unburnt area. Seed rain in the burnt area was not greater near to the forest than far from it. The abundance and richness of seed rain was positively correlated with tree density. Our findings highlight the lack of seed rain in burnt areas and differences in community composition between the burnt and unburnt areas. Collectively, these results indicate negative consequences on natural regeneration, which can lead to permanent secondarization of the vegetation and challenges for early regeneration of burnt areas, which will initially have impoverished forests due to low seed richness.

     

Contrasting Demographic Structure of Short‐ and Long‐lived Pioneer Tree Species on Amazonian Forest Edges

Although tropical forests have been rapidly converted into human‐modified landscapes, tree species response to forest edges remains poorly examined. In this study, we addressed four pioneer tree species to document demographic shifts experienced by this key ecological group and make inferences about pioneer response to forest edges. All individuals with dbh ≥ 1 cm of two short‐lived (Bellucia grossularioides and Cecropia sciadophylla) and two long‐lived species (Goupia glabra and Laetia procera) were sampled in 20 1‐ha forest edge plots and 20 1‐ha forest interior plots in Oiapoque and Manaus, Northeast and Central Amazon, respectively. As expected, pioneer stem density with dbh ≥ 1 cm increased by around 10–17‐fold along forest edges regardless of species, lifespan, and study site. Edge populations of long‐lived pioneers presented 84–94 percent of their individuals in sapling/subadult size classes, whereas edge populations of short‐lived pioneers showed 56–97 percent of their individuals in adult size classes. These demographic biases were associated with negative and positive net adult recruitment of long‐ and short‐lived pioneers, respectively. Our population‐level analyses support three general statements: (1) native pioneer tree species proliferate along forest edges (i.e., increased density), at least in terms of non‐reproductive individuals; (2) pioneer response to edge establishment is not homogeneous as species differ in terms of demographic structure and net adult recruitment; and (3) some pioneer species, particularly long‐lived ones, may experience population decline due to adult sensitivity to edge‐affected habitats.