Impact of commercial forest management on geophilous carabid beetles (Coleoptera: Carabidae) in tall,wet Eucalyptus obliqua forest in southern Tasmania

Abstract The impact of silvicultural practices (clearfelling, slash burning and sowing) on carabid beetle communities in tall wet Eucalyptus obliqua forests in southern Tasmania was examined using traplines of pitfalls in a chronosequence of regenerating coupes. Total species richness (n= 18) was modest compared to other temperate forests and was not systematically changed by forest management, although it was considerably lower in 20 year old regrowth than in younger regrowth or old-growth controls, possibly due to habitat simplification. The Shannon-Weiner Index was at a minimum in intermediate aged regeneration. TWINSPAN analysis assisted recognition of beetle communities typical of broad stages in the forest succession, with a major dichotomy between most old-growth sites plus young sites and intermediate plus advanced regeneration sites. Vector fitting of environmental variables in an ordination of the sites by non-metric multidimensional scaling revealed a significant influence for the age of regeneration and litter depth, but not bare ground percentage or soil pH. Survival of carabids in the habitat mosaic created by commercial forestry activity is likely to depend on both reinvasion from edges and survival of individuals in the fire-protected refuges that exist within the coupes. Pioneer species were winged, small in size, and non-endemic whereas the opposite was true of the fauna in the older sites. Carabids in eucalypt forests have good potential as indicators but their seasonality in occurrence demands that sampling be extended over most of the year.     

Effects of Clearfell Harvesting on Lucanid Beetles (Coleoptera: Lucanidae) in Wet and Dry Sclerophyll Forests in Tasmania

The effects of commercial forestry harvest and regeneration practices (clearfelling and slash-burning) on the lucanid fauna of the wet sclerophyll forests of southern Tasmania and the dry sclerophyll forests of eastern Tasmania were examined using pitfall catches. Lucanids are saproxylic beetles, dependent on dead, moribund and decaying wood. Samples taken from old-growth forest and from a chronosequence of sites regenerating after logging, in each forest type, were used to compare the species richness and abundance of the lucanid assemblages. In both forest types, species richness and abundance was highest in the youngest regeneration sites (1–3 year), reflecting the species richness of the original and adjacent unlogged forest, lowest in the older (20–25 year) sites, and variable in the old-growth sites. TWINSPAN cluster analysis showed no clear distinction between regeneration and old-growth forest. The post-harvest slash and stump residue provided an important refugium and initial habitat, but our research indicates that some species may not maintain populations in the long term. Our results suggest that most species of lucanids will find a continuous supply of suitable habitat only in old-growth forests; and such species may become less common as clearfell harvesting leads to a replacement of heterogeneous old-growth forest with single-aged monospecific stands. Continuity of supply of wood in all decay stages, the maintenance of sufficient source areas, and biological connectivity between old-growth stands to enable dispersal, are all likely to be essential to maintain lucanid beetle community integrity. If similar principles apply to other saproxylic species of invertebrate, then clearfelling and slash-burning may cause a gradual extinction of an important element of the forest biota.     

西双版纳热带森林土壤种子库与地上植被的关系

通过实验研究探讨了西双版纳几类热带森林的土壤种子库与地上植被的关系．结果表明,在森林演替的初期,土壤种子库与地上植被共有的种类和种子储量较多,随着林龄的增大,外来种子的比例逐渐增加,到季节雨林阶段,土壤种子库中的种子大部分为来自群落外的先锋种类．这些种子在郁闭的林冠下很难萌发,一旦森林受到干扰出现林窗或空旷地,这些潜在的种源将迅速萌发,参与植被的恢复或演替     

Exotic Guavas are Foci of Forest Regeneration in Kenyan Farmland

Fruiting trees in degraded areas are attractive for frugivorous birds and may become centers of regeneration. However, a number of tree species in degraded areas are exotic species. Thus, the question arises whether these exotic species can also act as foci for forest regeneration. In the farmland adjacent to Kakamega Forest, Kenya, we investigated the frugivore assemblage in, and seed rain and seedling establishment under, 29 fruiting exotic guava trees ( Psidium guajava ) at different distances to the forest. The results show that 40 frugivorous bird species visited guava trees. All of the seed and 82 percent of the seedling species found under the treecrowns were animal dispersed, 58 and 57 percent of them late-successional species, respectively. Path analysis revealed that the abundance of frugivorous birds, seeds, and seedlings did not decrease up to a distance of 2 km from the forest. Surprisingly, the abundance of frugivorous shrubland birds, animal-dispersed seeds, and late-successional seeds showed an increase with increasing distance from forest. Even though they are exotics, fruiting guava trees may have a positive effect on forest regeneration and might prove valuable for management plans concerning forest restoration.     

Mechanisms of plant regeneration during succession after shifting cultivation in eastern Amazonia

The role of seed bank, seed rain, and regeneration from seedlings and sprouts after swidden agriculture was compared in 5-, 10- and 20-year-old secondary forest and in a primary forest in Bragantina, Pará, Brazil. The seed bank (0–5 cm soil depth) was largest in the 5-year-old forest (1190 ± 284 seeds m⁻²) and decreased nearly ten-fold with age to 137 ± 19 seeds m⁻² in the primary forest. The highest seed rain was in the 5-year-old forest (883 ± 230 seeds m⁻² year⁻¹) and the least in the primary forest (220 ± 80 seeds m⁻² year⁻¹). Large plants (≥5 cm dbh) had more individuals and species that regenerated from sprouts than from seeds and the most abundant tree species in the secondary forest stands of all ages appear to be maintained by sprouting. The smaller individuals (≥1 m tall, <5 cm dbh) in the 5-year-old forest were mainly from sprouts, but those in the older secondary forests originated mainly from seeds. These results show that at the beginning of succession, although many species can be introduced to swidden fallow from seed bank and seed rain, it is the sprout that is the main source of recruits of primary forest species in secondary forests in Bragantina.     

Non-native plantation forests as alternative habitat for native forest beetles in a heavily modified landscape

The once extensive native forests of New Zealand’s central North Island are heavily fragmented, and the scattered remnants are now surrounded by a matrix of exotic pastoral grasslands and Pinus radiata plantation forests. The importance of these exotic habitats for native biodiversity is poorly understood. This study examines the utilisation of exotic plantation forests by native beetles in a heavily modified landscape. The diversity of selected beetle taxa was compared at multiple distances across edge gradients between each of the six possible combinations of adjacent pastoral, plantation, clearfell and native forest land-use types. Estimated species richness (Michaelis–Menten) was greater in production habitats than native forest; however this was largely due to the absence of exotic species in native forest. Beetle relative abundance was highest in clearfell-harvested areas, mainly due to colonisation by open-habitat, disturbance-adapted species. More importantly, though, of all the non-native habitats sampled, beetle species composition in mature P. radiata was most similar to native forest. Understanding the influence of key environmental factors and stand level management is important for enhancing biodiversity values within the landscape. Native habitat proximity was the most significant environmental correlate of beetle community composition, highlighting the importance of retaining native remnants within plantation landscapes. The proportion of exotic beetles was consistently low in mature plantation stands, however it increased in pasture sites at increasing distances from native forest. These results suggest that exotic plantation forests may provide important alternative habitat for native forest beetles in landscapes with a low proportion of native forest cover.     

Red spruce forest regeneration dynamics across a gradient from Acadian forest to old field in Greenwich,Prince Edward Island National Park,Canada

Red spruce forests have declined considerably throughout their range in the past decades. As agricultural fields are abandoned and land becomes available for reforestation, the possibility arises for red spruce forests to expand onto them. This study addresses the potential for red spruce forests to expand onto adjacent old fields in Greenwich, Prince Edward Island National Park, Canada. We examined red spruce distribution and abundance, plant species diversity and changes in community composition along a gradient from the interior of red spruce forests out towards the centre of adjacent old fields. Examining the patterns of red spruce distribution and abundance revealed that, where cultivation and logging have been abandoned recently in the fields and forests, regeneration is limited to the forest stands, but in the sites with older fields and forests, regeneration extends into and is more vigorous in the fields. Although species diversity varied from forest to field only for the tree and shrub layers, important changes occurred in the ground species composition. There is no evidence yet that the herbaceous species present in the forest stands will colonise the old fields. The results suggest that both environmental differences among sites and length of time since the fields were abandoned explain red spruce regeneration patterns. In order to more accurately assess the potential for red spruce regeneration in old fields, long-term monitoring of the production, dispersal and viability of red spruce seeds from adjacent forests and of the constraints to seedling establishment and survival in old fields will be needed.     

Alternative pathways of liana communities in the forests of northwestern Argentina

Liana dynamics in secondary and mature forests are well known in tropical areas dominated by native tree species. Outside the tropics and in secondary forests invaded by exotic species, knowledge is scarce. In this study, we compare liana communities between secondary and mature forests dominated by native species in a subtropical montane area of Sierra de San Javier, Tucuman, Argentina. Additionally, we evaluate changes of liana communities in secondary forests with increasing densities of Ligustrum lucidum and Morus alba, two of the most invasive exotic trees of the area. We surveyed liana species richness and density in three 30-year secondary patches, four 60-year secondary patches, and four mature patches dominated by native tree species, to analyze changes in liana communities with forest age. Within each patch, we sampled 10–25 20 × 20 m quadrats. Additionally, we surveyed liana density and species richness in secondary forest patches with different densities of L. lucidum and M. alba. In native-dominated forests, liana species richness increased and showed a tendency of increasing basal area from 30-year secondary forests to mature forests. Liana density was highly variable, and most of the species were shared between native-dominated secondary and mature forests. Liana density and species richness decreased with L. lucidum density, whereas in secondary forests highly dominated by M. alba, lianas increased in density. Overall, lianas followed different pathways influenced by native forest succession and exotic tree invasions.     

A comparison of litter beetle assemblages (Coleoptera) in mature and recently clearfelled Eucalyptus obliqua forest

Abstract  This study compares litter-dwelling beetles in mature wet eucalypt forest with those in young forest regenerated following clearfelling. The aims of the study were to determine the extent to which these forest ages support differing litter beetle assemblages, and to identify species characteristic of each age. Beetles were collected with pitfall traps in a spatially replicated study design to avoid confounding forest age and site differences. Three transects of traps were located in each of mature and young forest stands at four study sites. Beetle abundance was greatest in young forest, and young and mature forest supported distinctly different beetle assemblages. Of 37 commonly collected species, an indicator species analysis found 9 species characteristic of young logging regeneration, and 7 species characteristic of mature unlogged forest. These species could be useful in other Tasmanian studies concerning forest management impacts. Only two significant indicator species were carabids, suggesting that focusing only on carabids as indicators of forest management may be undesirable.     

Comparison of Restored and Mature Bottomland Hardwood Forests of Southwestern Kentucky

We evaluated 50-year-old bottomland forests in southwestern Kentucky restored from agriculture by planting and natural regeneration in terms of their development toward mature forests. We described and compared the structure and composition of the plant communities of three stands of each type (planted, naturally regenerated, and mature). Increment cores were analyzed to reconstruct developmental trends. Future trends were predicted from analyses of the midstory and understory composition. Both planting and natural regeneration adequately replaced the structural attributes of the historical bottomland forest. The existing structural differences are expected to diminish over time. Neither regeneration method replaced the wildlife value of the mature bottomland forests due to insufficient establishment and subsequent ingrowth of heavy mast species (particularly oaks and hickories). There was evidence that the understory species compositions of the restored forest types were similar to that of the mature stand type. All forests, including the mature stands, appeared to be succeeding from hydric to mesic species compositions as a result of human-altered hydrology and natural floodplain processes. We speculate that the historical bottomland species composition will probably not persist on any of the study sites in the long term.     

Extraction of non-timber forest products in the forests of Biligiri Rangan Hills,India. 2. Impact of NTFP extraction on regeneration,population structure,and species composition

Sustainable extraction of non-timber forest products (NTFPs) has recently gained considerable attention as a means to enhance rural incomes and conserve tropical forests. However, there is little information on the amounts of products collected per unit area and the impact of extraction on forest structure and composition. In this paper we estimate the quantities of selected products gathered by the Soligas, the indigenous people in the Biligiri Rangaswamy Temple (BRT) sanctuary in Karnataka, India, and examine the effect of extraction on forest structure and composition. Two sites, distant (DS) and proximal (PS), were identified based on the proximity to a Soliga settlement. The frequency of different size classes indicates that regeneration overall is poor in the area. The two sites show differences in species richness, basal area, and tree mortality. Furthermore, non-timber forest product species show a greater deficit of small size classes than the timber forest species, suggesting that regeneration is affected by collection of seeds and fruits from non-timber forest product species. Regeneration, however, may also be affected by other anthropogenic pressures such as fire, grazing and competition with weeds.     

The effect of seeds of exotic species transported via horse dung on vegetation along trail corridors

It has been suggested that exotic species will colonize within forests more frequently by the continual introduction of seeds through horse dung deposited along trails. Whether or not these exotic species have the ability to spread into and establish in the forest interior has been disputed. To address this, horse dung and soil samples were collected from trails during Autumn 1994 and Summer 1995 from three areas in southern Illinois, USA open to recreational horse travel. In addition, deer dung samples were collected from each of the study areas. Vegetation data were collected from each of the trail systems as well as from a trail along which horse travel was prohibited. The density of vascular plants in 0.25 m² quadrats placed at varying distances from the trail center to 5 m into the forest interior were recorded. Finally, dung samples were placed in situ along horse trails at one site to examine seedling germination in natural conditions. While 23 exotic species germinated from samples of horse dung placed out in a greenhouse, only one of these exotic species was also found in trail plots (Kummerowia striata). Similarly, while there were empirically more exotic species found along the trails allowing horse travel than there were on the trail lacking horse travel, the relative importance of those species was negligible along both trails. These results suggest that the emigration of exotic species via horse dung does not pose an immediate threat to the plant communities adjacent to trails in these forest systems. Nevertheless, the large number of exotic species in horse dung reflects the constant threat to any system from these species. Care must be taken, when allowing horseback use in areas, to anticipate invasion by exotic species from horse dung     

Impacts of Selective Logging and Agricultural Clearing on Forest Structure, Floristic Composition and Diversity, and Timber Tree Regeneration in the Ituri Forest, Democratic Republic of Congo

Mature tropical forests at agricultural frontiers are of global conservation concern as the leading edge of global deforestation. In the Ituri Forest of DRC, as in other tropical forest areas, road creation associated with selective logging results in spontaneous human colonization, leading to the clearing of mature forest for agricultural purposes. Following 1-3 years of cultivation, farmlands are left fallow for periods that may exceed 20 years, resulting in extensive secondary forest areas impacted by both selective logging and swidden agriculture. In this study, we assessed forest structure, tree species composition and diversity and the regeneration of timber trees in secondary forest stands (5-10 and ~40 years old), selectively logged forest stands, and undisturbed forests at two sites in the Ituri region. Stem density was lower in old secondary forests (~40 years old) than in either young secondary or mature forests. Overall tree diversity did not significantly differ between forest types, but the diversity of trees ≥10 cm dbh was substantially lower in young secondary forest stands than in old secondary or mature forests. The species composition of secondary forests differed from that of mature forests, with the dominant Caesalpinoid legume species of mature forests poorly represented in secondary forests. However, in spite of prior logging, the regeneration of high value timber trees such as African mahoganies (Khaya anthotheca and Entandrophragma spp.) was at least 10 times greater in young secondary forests than in mature forests. We argue that, if properly managed and protected, secondary forests, even those impacted by both selective logging and small-scale shifting agriculture, may have high potential conservation and economic value.     

Are streamside buffers edge-affected habitat for ground-dwelling forest beetle assemblages?

Reservation of forest in riparian buffers is common practice in commercial forestry areas worldwide, potentially providing valuable habitat for biodiversity dependent on mature forest. However, the habitat value of narrow reserve corridors can be compromised by edge effects. We investigated the habitat value of streamside buffers in wet eucalypt forest for ground-dwelling beetles in Tasmania, Australia. Beetles were collected with pitfall traps in five replicates of four habitats: unlogged corridors of mature forest in streamside reserves (buffers) with clearfelling-derived logging regeneration either side; continuous mature upslope forest; continuous mature riparian forest; and <20-year-old upslope clearfelling-derived logging regeneration. Streamside reserve widths on each side of the stream were on average 40 ± 6 m (±95% CI) from reserve edge to stream. Beetle assemblages in logging regeneration differed substantially from those in the unlogged habitats, including the streamside reserves. Streamside reserve assemblages nevertheless differed from those of the continuous unlogged areas. Assemblage composition in streamside reserves was most similar to that in continuous mature riparian forest, although beetle diversity was higher in the reserves. Our results suggest that although streamside reserves provide habitat for the majority of commonly collected beetle species occurring in continuous mature forest, wider reserve corridors in the wet eucalypt forests of Tasmania may be required to provide habitat that is not edge-affected.     

Soil seed banks in dry Afromontane forests of Ethiopia

Abstract. The soil seed bank was investigated in four dry Afromontane forests of Ethiopia. At least 167 plant species were identified in the 0–9 cm soil layer with total densities ranging between 12 300 and 24 000 seeds/m². Herbs were represented with the largest numbers of species and seeds in the seed bank, while the contribution of tree species was generally low. The overall vertical distribution of seeds was similar at all sites with the highest densities occurring in the upper three cm of soil and gradually decreasing densities with increasing depth. Relatively high densities also occurred in the litter layer. There were large differences in depth distribution between species, suggesting differences in seed longevity. A large number of species in dry Afromontane forests evidently store quantities of seeds in the soil and this is in contrast to the situation in most tropical rain forests, dry lowland forests and savannas, where both the number of seeds and the number of species are relatively small. It is possible that the strongly seasonal and unpredictable climate of this region may have selected for high levels of dormancy, and that herb regeneration is associated with small scale disturbance. The fact that most of the dominant tree species do not accumulate seeds in the soil suggests that their regeneration from seed would be unlikely if mature individuals disappeared. Most tree species have relatively large seeds and poor long-distance dispersal; this implies that restoration of Afromontane forests after destruction would be difficult. Since there is a diverse seed bank of the ground flora, this component of the vegetation would have a better chance of reestablishing. However, because most cleared forest land is used for agricultural crop production, it is probable that the seed bank will be depleted in only a few years. Therefore, the future of the Afromontane forest flora seems to depend on the successful conservation of the few fragments of remaining natural forest.     

Impacts of logging on density-dependent predation of dipterocarp seeds in a South East Asian rainforest

Much of the forest remaining in South East Asia has been selectively logged. The processes promoting species coexistence may be the key to the recovery and maintenance of diversity in these forests. One such process is the Janzen-Connell mechanism, where specialized natural enemies such as seed predators maintain diversity by inhibiting regeneration near conspecifics. In Neotropical forests, anthropogenic disturbance can disrupt the Janzen-Connell mechanism, but similar data are unavailable for South East Asia. We investigated the effects of conspecific density (two spatial scales) and distance from fruiting trees on seed and seedling survival of the canopy tree Parashorea malaanonan in unlogged and logged forests in Sabah, Malaysia. The production of mature seeds was higher in unlogged forest, perhaps because high adult densities facilitate pollination or satiate pre-dispersal predators. In both forest types, post-dispersal survival was reduced by small-scale (1 m(2)) conspecific density, but not by proximity to the nearest fruiting tree. Large-scale conspecific density (seeds per fruiting tree) reduced predation, probably by satiating predators. Higher seed production in unlogged forest, in combination with slightly higher survival, meant that recruitment was almost entirely limited to unlogged forest. Thus, while logging might not affect the Janzen-Connell mechanism at this site, it may influence the recruitment of particular species.     

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.     

Is <Emphasis Type="Italic">Pinus radiata</Emphasis> invading the native vegetation in central Chile? Demographic responses in a fragmented forest

Forest fragmentation facilitates the invasion of exotic species. This threat may be especially severe if forest fragments are surrounded by plantations of exotic species like Pinus radiata, an aggressive colonizer and shade-intolerant tree that has invaded successfully several native ecosystems of the southern hemisphere. In this study, we experimentally tested if the conditions of a successful seedling establishment P. radiata are fulfilled at the Coastal Maulino forest, an endemic fragmented forest of central Chile. Results demonstrated that seeds are dispersed into the native forests, however seedling establishment occurs only at the edges. We conclude that this exotic species is not invading native forests up to date. However, we suggest to conduct evaluations of seed rain and seedling establishment in the long term, in order to monitor the fate of this exotic species in fragmented native forest of Central Chile.     

Restoration of semi-natural forest after clearcutting of conifer plantations in Japan

We reviewed recent studies on the restoration of semi-natural forests after clearcutting of conifer plantations with specific reference to the importance of setting restoration goals, general and specific factors influencing restoration, and the prediction and judgment of successful restoration. For the restoration of semi-natural forests following the clearcutting of conifer plantations, recovery levels and appropriate restoration methods cannot be considered separately from the aims of restoration to provide ecosystem services. Restoration needs to be based on the setting of goals that correspond to the type and degree of ecosystem services targeted. When we aim to restore vegetation dominated by late-seral canopy trees within as short a period after the clearcutting of conifer plantations as possible, advanced regeneration in the pre-logged plantation is the most important and reliable source of post-logging regeneration, just as it is in the recovery of disturbed non-plantation forests. Advanced regeneration is not always present in plantations. Seedling establishment by seed rain from adjacent natural forest patches after a disturbance can contribute to late-seral or canopy species; however, the range of the edge effect is generally short, and the degree of the edge effect depends on the natural forest type and is more pronounced in deciduous forests, such as those in cool-temperate climates, or in forests with a complex forest structure. Thus, advanced regeneration is a better predictor of short-term forest recovery than measures based on seed rain from adjacent seed sources. However, restoration achieved only through advanced regeneration can simplify the species composition, and the recolonization processes of gradual species accession from seeds should be considered in the long-term context of restoration.     

Postdispersal seed predation and seed viability in forest soils: implications for the regeneration of tree species in Ethiopian church forests

Almost all dry Afromontane forests of Northern Ethiopia have been converted to agricultural, grazing or scrub lands except for small fragments left around churches (‘Church forests’). Species regeneration in these forests is limited. We investigated (i) how intense postdispersal seed predation was in church forest, and if this seed predation varied with species and/or habitat, and (ii) for how long tree seeds maintained their viability while buried in forest soil. In the seed predation experiment, we monitored seeds of six tree species in four habitats for a period of 14 weeks (the peak seeding season). In the seed viability experiment, we assessed seed viability of five species in four habitats after being buried 6, 12, or 18 months. Ninety‐two percent of the tree seeds were predated within 3.5 months. Predation was mainly dependent on species whereas habitat had a weaker effect. Seed viability decreased sharply with burial time in soil for all species except for Juniperus. To minimize seed availability limitation for regeneration of such species in the forest, the standing vegetation needs to be persistently managed and conserved for a continuous seed rain supply. Additional seed sowing, and seed and seedling protection (by e.g. animal exclosures) may increase successful regeneration of important species in these forests.