Recovery of conservation values in Central African rain forest after logging and shifting cultivation

Secondary forests in Central Africa are increasing in importance for biodiversity conservation as old growth forests outside the few protected areas are disappearing rapidly. We examined vegetation recovery in a lowland rain forest area in Cameroon based on a detailed botanical survey of old growth forest and different-aged logging gaps (5–27 years) and shifting cultivation fields (10–60 years). Our analysis focuses on the long-term recovery of botanical conservation values by analysing trends in vegetation structure, species composition, species diversity and levels of endemism and rarity. In the total survey (4.25 ha), we recorded 834 species of which 23% were endemic to the Lower Guinea forest region. The proportion of endemic species was high in shrubs and low in herbs. Geographic range and (local) rarity were not significantly associated. The proportion of rare species (relative frequency <10%) was high in woody climbers and low in trees. In logging gaps, recovery of all vegetation characteristics was relatively quick (5–14 years). Recovery in shifting cultivation sites took longer (30–60 years). Endemic species were found to be highly sensitive to shifting cultivation practices and even after 50–60 years the level of endemism was still significantly lower compared to old growth forest. The proportion of rare species was not significantly different between disturbed sites and old growth forest. We conclude that secondary forests can contribute to biodiversity conservation, e.g. as buffer zones around protected areas. However, this contribution should be assessed differently between land use types and widespread versus endemic species.     

Tropical seasonal forests in monsson Asia: With emphasis on continental southeast Asia

This paper is intended to provide a brief review of the tropical seasonal forest, one type of the tropical moist forests in monsoon Asia. It will also focus on and summarise issues of current concern in relation to their depletion and global environmental issues. Tropical moist forests occur in the rainy tropical and monsoon tropical climate types. The tropical moist evergreen forest or the tropical rain forest, which account for two-thirds of the tropical moist forests are rich in biodiversity and contain valuable tropical hardwood. The tropical moist deciduous forest or the tropical seasonal forest which lie along the fringes of tropical rain forest, are less complex than the tropical rain forest and have more distinct wet and dry periods. Broadleaved deciduous trees of the genera Tectona, Shorea, and Dipterocarpus are predominantly in this forest type. Currently estimates have found that more than 17 million hectares of forest mainly tropical moist forests are being lost each year. There is a widespread recognition that agriculture and the burning of tropical moist forests contribute to global warming but to a much lesser extent than the combustion of fossil fuels and industrial activities in the developed world.     

Edge effects and tropical forest canopy invertebrates

The term edge effect can be used to encompass a wide range of both biotic and abiotic trends associated with boundaries between adjacent habitat types, whether these be natural or anthropogenic. Edge effects have been shown to represent significant forces affecting both faunal and floral assemblages in fragmented ecosystems. Specific studies of faunal assemblages associated with habitat edges have revealed trends at all levels of biological organisation from individuals to communities.Studies of edge effects on invertebrates in tropical forests have been relatively scarce. In this paper we review the nature and organisation of edge effects, focusing upon the processes which may lead to detrimental consequences for both forest canopy invertebrates and the forests themselves. We present as a case study data illustrating the very large amount of variance (over 50%) in community structure that is predicted simply by abiotic (microclimatic) variables in both a tropical and a temperate forest edge. We summarise major features of edge effects amongst forest invertebrates, stress the inter-relatedness of edge and canopy biology, and present an agenda for study of the canopy as an edge.     

Managing genetic variation in tropical trees: linking knowledge with action in agroforestry ecosystems for improved conservation and enhanced livelihoods

Tree species in agroforestry ecosystems contribute to the livelihoods of rural communities and play an important role in the conservation of biodiversity. Unless agroforestry landscapes are productive, however, farmers will not maintain or enhance the range and quality of tree species in them, and both income opportunities and biodiversity will be lost. Productivity depends on both tree species diversity and genetic (intra-specific) variation, but research on the latter has until recently not received the recognition it deserves. Worse, when knowledge on tree genetic variation in agroforestry systems has become available, it has not generally been linked in any systematic way with management, indicating a disjunction between research and field-level practice. In this essay, we attempt to bridge this gap by considering three questions: why is genetic diversity important in tree species? What is our current state of knowledge about intra-specific variation in trees in agroforestry systems? And, finally, what practical interventions are possible to support the conservation of this diversity in agricultural landscapes, while enhancing farmers’ livelihoods? A wide genetic base in agroforestry trees is essential to prevent inbreeding depression and allow adaptation to changing environmental conditions and to altering markets for tree products. Recent evidence shows, however, that many species are subject to poor germplasm collection practice, occur at low densities in farmland, and are found in highly aggregated distributions, all of which observations raise concerns about productivity and sustainability. A range of germplasm-access based interventions is necessary to improve current management, including the enhancement of community seed- and seedling-exchange networks, and the development of locally based tree domestication activities. Equally necessary, but more difficult to address, is the development of markets that support genetic diversity in tropical tree species; we discuss approaches by which this may be undertaken.     

Growth and mortality of trees in Amazonian tropical rain forest in Ecuador

Abstract. Structural changes are analysed in four samples representing 4 ha, two line transects and two hectare plots, of Amazonian tropical lowland rain forest in northern Ecuador. Only trees with a DBH ≥ 10 cm were included. A sample of floodplain forest in Añangu represents the largest turnover found in tropical forests (stand half-life = 23 yr). The line transect and hectare plot both of tierra firme forest in Añangu have the same turnover (37 yr) and were balanced for death and in-growth of both individuals and wood (basal area). The 1-ha tierra firme sample in Cuyabeno had a turnover of 67 yr and was in a growing phase. The floodplain line transect in Añangu was in a phase of structural breakdown. However, the floodplain line transect had the largest growth of basal area per tree (23.4 cm²/yr). The tierra firme samples had a growth of 9.6, 10.1, and 13.6 cm²/yr. Most of the dead trees fell with some uprooting in three of the four samples. However, no significant difference in the distribution of mode of death was found between the four samples. Death was independent of topography and the dead trees were randomly distributed. As the trees grow up they occupy more space and larger trees (DBH ≥ 15 cm) become more uniformly distributed, whereas smaller trees (DBH ≤ 15 cm) were randomly distributed. Our study confirms that plots of 1 ha are not sufficient to include representative samples of different stages of forest structure.     

Habitat preferences of oak-feeding xylophagous beetles in a temperate woodland: implications for forest history and management

Oaks host the richest fauna of saproxylic insect in Europe. We studied habitat preferences of two beetle families, Buprestidae and Cerambycidae, by rearing the beetles from standardised oak timber baits. Species density was higher in the understorey than in the canopy; and in sun-exposed baits if within the understorey. Insolation was the most important factor affecting the composition of reared assemblages (explaining ca. 30% of variation in the data), followed by vertical stratum (ca. 10%). Local dead wood volume had no effect. The high preference for sun-exposed wood located near the ground suggests that: (i) open-canopy woodlands had to be rather common in temperate Europe; (ii) oak-utilising xylophages would benefit from restoration of management practices such as coppicing or woodland pasture; (iii) the policy of increasing dead wood volume in commercial forests is principally correct, but its success will depend on dead wood location within the forests.     

Sustainable use of tropical forests by reduced-impact logging in Deramakot Forest Reserve,Sabah, Malaysia

In pursuance of economic growth and development, logging has exhausted the natural timber resource in the tropical rainforest of Sabah, Malaysia. Realizing the forest depletion, the Sabah Forestry Department, with technical support from the German Agency for Technical Cooperation, begun developing a management system with the intent of managing all commercial forest reserves in a way that mimics natural processes for sustainable production of low volume, high quality, and high priced timber products in 1989. As dictated by a forest management plan based on forest zoning, about 51,000 ha of the entire area is set aside for log production and 4,000 ha for conservation in Deramakot Forest Reserve, Sabah, Malaysia. This Forest Management Plan has served as the blueprint for operational work and biodiversity conservation in Deramakot to the present. A strict protection area is set aside for biodiversity conservation within the reserve. A reduced-impact logging system is being employed for harvesting with minimal impacts on the physical environment. Deramakot Forest Reserve was certified as “well managed” by an international certification body, the Forest Stewardship Council, in 1997 and is the first natural forest reserve in Southeast Asia managed in accordance with sustainable forestry principles. In addition to providing a "green premium," certification provides easier market access, evidence of legality, multi-stakeholder participation, conservation of biodiversity and best forest management practices, particularly reduced-impact logging techniques. Deramakot Forest Reserve is the flagship of the Sabah Forestry Department and serves as a symbol of what can be achieved with political support and institutional commitment.     

Patterns and trends in tropical forest cover

Abstract

In the 2005 edition of the Global Forest Resources Assessment of the Food and Agriculture Organization of the United Nations, a moderate negative trend was reported regarding the change of tropical forests: the net annual change was estimated at ?11.8 million ha for the period 2000–2005, while the rate was ?11.65 for the previous decade. Tropical Asia showed the highest rate and most negative trend, passing from ?0.8% to ?0.96% per year. The remote sensing survey done for previous Forest Resource Assessment editions covering the period 1980–2000 revealed distinct change processes in the three tropical regions. Survey results indicated that socio‐economic and cultural aspects that characterise and differentiate the geographic regions determine the nature of the change processes and underlying cause–effect mechanisms, while the ecological setting determines the intensity of change and reveals its environmental implications. A comparison of deforestation processes of the two decades indicated an on‐going process of “radicalisation” of the dynamics determined by an increasing frequency of high‐gradient changes (e.g. total clearing rather than fragmentation and degradation) and by a shift of deforestation fronts towards wetter zones, with a consequent higher per‐hectare carbon emission associated with deforested areas.     

Spatio-temporal patterns of tree community dynamics in a tropical forest fragment in South-east Brazil

The tree community (dbh > 5 cm) of a fragment of tropical montane semi-deciduous forest in South-east Brazil was repeatedly surveyed over a 19-year period in order to assess spatial and temporal patterns of dynamics. The surveys took place in 1987, 1992, 1996, 2001, and 2006 in a grid of 126 20 × 20 m permanent plots covering almost the entire fragment (5.8 ha). Overall patterns indicated that a self-thinning process has taken place in the fragment since 1992. Community dynamics varied in space and time, with most dynamics highly spatially clustered. With exception of mortality rates, there were no changes in the spatial patterns of community dynamics through time. No relation between edges and dynamics variables was found. Most species with increasing density and basal area were shade-bearers, while most decreasing species were canopy light demanders and pioneers.     

Tree species diversity in small, tropical riparian forest fragments in Belize, Central America

Tree species diversity was measured in a network of very small galleryforests within the Mountain Pine Ridge savanna in Belize. Research focussed onforest patches smaller than 1 ha in size (micro-forests) and linearstrips of trees along creeks lacking interior core zones with low understoreylight levels (tree thickets). Twenty-five micro-forests and 51 tree thicketsites were sampled throughout the savanna. A total of 144 morphospecies 5cm dbh (106 in micro-forests and 117 in tree thickets) werefound, which represents 1/5 of the approximately 700 native tree species in Belize.Most (85.3%) of the species encountered are typically found in tropical rainforests and few are restricted to savanna or riparian environments. Speciesaccumulated at a much faster rate in micro-forests than in tree thickets. Onlyone species, the palm Acoelorraphe wrightii, was extremelyabundant, accounting for almost 30% of all stems. Many of the species werepresent in very low densities: 19% of all species found in micro-forests and 42%of those found in tree thickets had on average one or fewer stems per hectare. Alarge proportion of species were also found infrequently across the landscape,being present in only 36% of micro-forests and at 52% of tree thicket sites. Theresults indicate that networks of very small forest patches can contain highnumbers of species and could therefore contribute to the maintenance of regionalbiodiversity.     

Unfavorable successional pathways and the conservation value of logged tropical forest

Conservation agencies are increasingly advocating that the survival of many tropical forest species may depend on disturbed forests and are directing scarce conservation resources to managing logged forests. This requires critical evaluation. In this 10-year study, we quantify tree community dynamics in three selectively logged areas harvested at different intensities and compare their recovery to two unlogged areas in Kibale National Park, Uganda. Over the 10 years, 527 of the original 4840 tagged trees (10cm DBH) died; while the mortality rate was highest in the heavily logged area, it was only significantly greater than one of the unlogged sites. The density of new trees varied significantly among areas being highest in the lightly logged area, but the density of new recruits in the heavily logged area did not differ from the unlogged areas. Overall, the more heavily logged areas had higher growth rates than the unlogged or lightly logged areas. However, there was no difference among areas in the magnitude of the change in basal area; and in both 1990 (20+ years post-harvest) and 2000 the basal area in the heavily logged area was significantly less than the unlogged areas. In general, findings from the heavily logged area suggest that the expectation that in logged areas a number of processes of forest regeneration will be accelerated relative to unlogged forest was not met. Thus, 30+ years after logging evidence suggests that forest recovery will be slower than expected. We also present evidence to suggest that the climate in the region is changing, which may account for changes in the population dynamics of certain species in the unlogged forests.     

The Atlantic forest in the Volta Velha Reserve: a tropical rain forest site outside the tropics

With its very broad latitudinal extension (from 5° to 30°S), Brazil's Atlantic Rain Forest includes sites that wouldnot be classified as tropical by commonly used climatic classificationsystems. This situation particularly holds for the sites nearthe southern limits of this ecosystem. The goal of this study was to assess forest floristic composition, physiognomic aspects (deciduousspecies, leaf types, leaf area index) and reproductive biology (monoecious/dioeciousspecies, pollination syndromes and dispersal syndromes) of the Atlantic forest in the Volta VelhaReserve, southern Brazil (26°04 S, 48°38 W Gr). The research focuses on theaffinities of this site, which lies outside generally accepted boundaries for tropical forest. Theresults demonstrate that Volta Velha has a typically tropical floristic composition, apparentlymaintained by local climatic conditions. The differences between the characteristics of the VoltaVelha forest and those of other tropical stands are within the range of differences observed amongclassically defined tropical sites.     

Frugivorous butterfly species in tropical forest fragments: correlates of vulnerability to extinction

Insects exhibit a variety of population-level responses to forest fragmentation, ranging from population increase to extinction. However, the biological attributes that underlie differences in extinction vulnerability among insects have been little-studied. Using the frugivorous butterfly community of tropical dry forest in Venezuela, we studied body size, population density and colonization ability as attributes that might underlie the range of responses of insects to forest fragmentation. The study was carried out in a set of forest fragments in the reservoir Lago Guri, formed by the damming of the Caroni River in eastern Venezuela. Results show that larger butterfly species were more vulnerable to extinction from habitat fragments than smaller ones. Rarer species were not more vulnerable to extinction, showing that rarity may not be an important correlate of vulnerability to extinction amongst insects. Contrary to expectation, faster-flying species were more and not less vulnerable to extinction from small habitat fragments. We speculate on the possible reasons for the observed patterns in extinction vulnerability using additional observations on behavioural patterns and larval host plant distributions of some of the butterfly species.     

Woody vegetation structure of xeric forest stands under different edaphic site conditions and disturbance histories in the Biosphere Reserve 'Parque Costero del Sur', Argentina

We studied stand structures and soil properties in an old-growth forest and two 30-yr-old second-growth stands. In the old-growth forest, the total density and basal area average 1566 trees > 1.25 m height ha^-1 and 46.73 m² ha^-1. The dominant trees are Scutia buxifolia and Celtis tala. Using multivariate techniques we distinguished three stands: PS1, dominated by S. buxifolia, is 1000 m far from the river. Its soil is shallow and loamy. PS2 and PS3, co-dominated by S. buxifolia and C. tala, are over 1200 m distant from the river. There the soil is deeper and has thicker texture and higher phosphorus and calcium concentrations than the near-the-river forest soil. Scutia buxifolia shows reverse J-shaped size-distributions and has morphological features of stress-tolerant species. Celtis tala shows oscillating decay size-curves that suggest recruitment pulses related to small gaps and it has morphological features of competitive species. Celtis tala was selectively cut in the past in the second-growth stands SNRD and SRD. The stand SNRD, 1000 m far from the river, is dominated by S. buxifolia. The second species is Schinus polygamus which presents the bell-shaped size-structure of the pioneer species. SNRD does not differ from its old-growth counterpart PS1 in total tree density, basal area and tree branching. The stand SRD, over 1200 m distant from the river, is co-dominated by S. buxifolia and by C. tala trees regenerated from stumps. SRD does not differ from its old-growth counterparts PS2 and PS3 in total tree density and basal area. As to tree branching, it does not differ from PS3, but differs from PS2. All the stands are being invaded by the exotic tree Ligustrum lucidum.The differences between the old-growth stands seem to be related to the gradients of soil texture and nutrient concentrations raising edaphic stress towards the river. In SNRD, the stress, the stress-tolerance of S. buxifolia, and the aptitude of S. polygamus to recruit in disturbed habitats seem to have prevented the post-logging recruitment of C. tala. In SRD, C. tala regenerated possibly due to a better competitive performance in a more favorable site. Under protection the second-growth stands recovered the old-growth quantitative features. We recommend the restoration of the qualitative features and the control of L. lucidum.     

Shrew species diversity and abundance in Ziama Biosphere Reserve, Guinea: comparison among primary forest, degraded forest and restoration plots

The aim of our study was to compare the shrew community diversity and structure in gradients of tropical forest degradation and restoration. Four plots within each of six habitats of the Ziama Biosphere Reserve were surveyed, including primary forest, secondary forest, cultivated fields, recently (less than 3 years) abandoned fields, young (10–12 years) forest restoration plots, and old (34 years) restoration plots. From August to November 2003, we pitfall-trapped 2,509 shrews representing 11 species. Shrew species richness and composition was similar in the six habitat surveyed, while shrew species abundance varied between habitats. Canopy height and cover, density of stems and trees and understorey density were shown to constitute important parameters influencing the abundance of several shrew species. After clear-cutting, restoration of key attributes of the forest vegetation structure was possible in 10–34 years, either by natural regeneration or by planting of seedlings. The relative abundance of most shrew species was similar between restoring forest (i.e., young restoration plots or fallows) and primary forest. Considering the advantages and disadvantages of these two methods of forest restoration, one of the most suitable management practices to restore forest while preserving shrew biodiversity could be to perform an alternation of native seedling plantation lines and fallows.     

Diversity of dung and carrion beetles in a disturbed Mexican tropical montane cloud forest and on shade coffee plantations

This paper analyzes the diversity of dung and carrion beetles (Scarabaeinae and Silphidae) in four human-induced habitats of a disturbed tropical montane cloud forest: polyspecific shade coffee plantations, monospecific shade coffee plantations, tropical montane cloud forest fragments, and clear cuts. The four habitats had similar richness, species composition, and assemblage structure of dung and carrion beetles. Differences were found in abundance and biomass levels for the four dominant species in the landscape. Dung beetles were more abundant than carrion beetles, but the biomass was higher for the latter. Carrion beetles were seasonal, while dung beetles were clearly not. When forest fragments and shade coffee plantations were compared to other similar habitats in the region, the same general pattern was observed. However, forests with high disturbance and monospecific shade coffee plantations had lower species richness than forests with low and medium disturbance and polyspecific shade coffee plantations. Thus shade coffee plantations maintain connectivity between patches of cloud forest in a landscape that is strongly affected by human activities. Protecting landscape diversity appears to ensure high species richness.