Forest and Nature Conservation

Dry tropical forests provide a wide range of forest products that directly support the livelihoods of people. These forests are the most threatened and least protected forests due to expansion of agriculture and pasture lands, unregulated grazing, forest fire, unregulated collection of wood and other forest products. Dry forests of Ethiopia are heavily affected by such human induced factors. The iconic Boswellia papyrifera (Del.) Hochst is a dominant tree species of this forest and the principal source of the globally traded frank-incense. The species lacks regeneration in all forests evaluated so far. Frankincense forests in relatively wetter dry land areas with little or no human related disturbance are not evaluated so far. Here we quantified the regeneration status of the frankincense tree in such areas and evaluated these forests in comparison to non-regenerating frankincense forests elsewhere. We surveyed two-ha plots in each of five districts in Benishangul Gumuz Region, Western Ethiopia. The frankincense tree populations showed two different regeneration patterns: inverse J-shaped and bell-shaped pattern. The presence of regenerating populations in three of our study areas is in sharp contrast to all earlier studies on this species. The healthy regeneration might be related with the availability of more favourable conditions such as better precipitation, lower levels of anthropogenic disturbances and younger ages of the three woodlands. These unique, regenerating frankincense tree populations need recognition and should be delineated as priority areas for conservation, which includes their role as source of genetic material. Better attention of conservation practitioners, policy makers and frankincense companies may help this species to survive and therewith its emblematic frankincense.

The application of biomass models for quantifying forests’ above-ground biomass is essential for sustainable forest management. However, lack of knowledge in modelig biomass of individual tree growth hinders the sustainable management of Dry Afromontane forests. In this study, models to estimate above-ground biomass were developed for Rhus ruspolii, Ekebergia capensis, and Nuxia congesta. To develop the models, a total of 45 trees from different diameter classes were selected, felled, and divided into different biomass compartments. For the model’s development, diameter at breast height (DBH), total height (TH), diameter at stump height (DSH), and wood density (WD) were used as independent variables. Models’ performances were evaluated using RSE, adjusted coefficient of determination, and AIC. Also, model validations were done by using rRMSE, mean absolute deviation, bias, and coefficient of variation. Models 5 (Adj-R2 = 0.92), 6 (Adj-R2 = 0.97), and 8 (Adj-R22 = 0.82) were the best...

A key problem for conservation is the coincidence of regions of high biodiversity with regions of high human impact. Twenty-five of the most threatened centers of plant diversity were identified by Myers et al., and these" hotspots" play a crucial role in international conservation strategies. The primary goal of the hotspots is to cover the most threatened centers of plant diversity, but their efficacy has not yet been tested empirically. For sub-Saharan Africa, our study evaluates the hotspots postulated by Myers and compares them ...

Plant species diversity is surveyed in the southern part of the Taı¨National Park (TNP), Coˆte d'Ivoire. This park is the largest remaining tract of pristine forest in the West African rainforest biodiversity hotspot. Plant assemblages and environment factors were surveyed in 39 temporary 625-m 2 plots within three areas. The species list was completed thanks to itinerant prospections. TWINSPAN classification and detrended correspondence analysis were applied to the 39 releve´s. We recorded a total of 916 plant species, including 169 West African endemics, that rises the floristic richness of TNP in 1233 species. Most plant species recorded were Guineo-Congolian species (90.9%) among which 8% were 'Sassandrian species', i.e. endemics of the extreme southwest Coˆte d'Ivoire. Eight of these endemics were exclusive of the southern part of TNP. The forest is very species-rich, particularly in Rubiaceae, Leguminosae and Euphorbiaceae. Most of the sampled species (59.5%) were erect phanerophytes with a dbh £ 10 cm. We distinguished 7 plant community types, mainly determined by geomorphology and disturbance history. Lowland forests were typical dense evergreen forests with different degrees of maturity related to historical human impact. Inselbergs and swampy depressions provide an original azonal vegetation. We conclude that the southern part of TNP contributes significantly to the regional biodiversity hotspot since it includes the last remnants of primary evergreen rainforest and contains species assemblages from both higher rainfall biomes on moist soils derived from schist parent material and lower rainfall biomes on inselberg slopes and top. As anthropogenic disturbance clearly reduces biodiversity, these last remnants should be integrally protected.

Regional variation in the characteristics of gaps larger than I 0 m 2 was determined for three forest sites on different soils, along a climatic and vegetation gradient in the tropical moist forest of Tat National Park, Ivory Coast. The total inventoried area was 71 ha. The three sites were strikingly similar with regard to gap density, gap size distribution, and total gap area. Average gap density was 2.1 gaps ha_,, of which 0.7 gaps ha ·• were estimated to have been created during the last year. Average gap size was 41 m 2 (55 m' for newly formed gaps). Total gap area was on average 0.8 percent of the total inventoried area, versus 0.4 percent for the gaps formed during last year.

Results of silvicultural experiments in Surinam, carried out since 1965, have shown that volume increment of marketable timber species can be effectively stimulated by treatments such as liberation and re®nement. Such re®nement might, for example, initially reduce the basal area of non-marketable species from ca. 20 to 6 m 2 /ha and the total basal area to some 10 m 2 /ha. The effects of these treatments, however, generally last for limited periods of <10 years. Even in a forest management set-up with relatively short felling cycles of 20±30 years, treatment has to be repeated to be fully effective. In three experiments, including a large-scale ®eld trial, the treatment stimulated increment and recruitment but both slowed down markedly with time. Mortality is variable, but has a tendency to increase with stronger interferences. The large-scale ®eld trial, which had received a single initial treatment, has grown enough volume for a second harvest of 20±30 m 3 /ha after 20 years. Increment and ®nal stand structure would have been much improved with three treatments during the cycle as originally planned. # 1999 Elsevier Science B.V. All rights reserved.

The spatial distribution of canopy gaps was analysed on three sites (total 71 ha) in the tropical moist forest of Tal National Park, Ivory Coast. Pattern analysis revealed a clustered distribution of gaps for two of the three sites. Catena dependent gap formation processes might explain local differences in the occurrence and distribution of gaps. Gap densities, sizes and percentage forest area in gap phase are higher on the upper and middle slope than on the crest or lower slope. As a consequence, regeneration of gap dependent tree species might be directed to the catena positions with the highest disturbance regime. The spatial distribution of gap dependent species can be clumped, not only due to the regeneration within gaps, but also due to the clustered nature of gap distribution on its own.

The occurrence and abundance of 12 canopy tree species from the moist tropical forests of West Africa have been studied in relation to a climatic gradient. We focused on environmental factors related to water availability: annual amount of rainfall, the length of the dry season, and cumulative water deficit. Species occurrence and abundance data are used for 39 forest sites in Liberia and southwest Cote d'Ivoire. Species responses are modelled using a set of five increasingly complex models, ranging from a no-trend model to a skewed bell-shaped response curve.

A comparison is made between acidification and the climate change problems. The common cause and the variety of effects with an impact on many different ecosystems and aspects of society are discussed. A number of specific aspects of environmental pollution research are highlighted. For the Dutch Climate Change Program 1995-2000, a more system-oriented approach in stead of an effectoriented approach is chosen. Research should determine the degrees of freedom the society has to manage these different systems.

Which areas need most urgently conservation effort? How can we make a worldwide priority list of biodiversity hotspots the most threatened? How much detail do we need in plant distribution data, e.g. for Africa, to answer these questions reliably? Conservation gap analysis is in fashion in America since a couple of decades. Using geographic information systems, the distribution of threatened species is crossed with the protected area network with the purpose of planning additional conservation effort in areas that need it most. Conservation gaps are detected: areas providing habitat for species underrepresented in the protected areas. For a presentation at the 5th World Parks Congress (Durban, September 2003), we developed an alternative strategy for assessing the representativeness of the world’s protected area system (i.e. the extent to which this system includes samples of all elements of biodiversity). Information on the distribution of biodiversity is often mapped at a very coa...

The Tropenbos Cote d&#39;Ivoire Programme provides scientific support to the Autonomous Project for the Conservation of Ta&quot;i National Park (PACPNT). Within this framework, three sectors in the South of the Park, south of Hana River near Guiroutou, Dogbo and Djapadji, were botanically surveyed between March 1998 and January 1999. On 39 sample plots of 35 by 35 m (13, 15 and 11 per sector), and along transects, 1242 herbarium voucher specimens have been collected, belonging to 413 species. On each sample plot, the two upper mineral soil layers and the organic soil layer have been sampled at three places along the slope within the plot, and have been analysed. Four catenas have been described, one per sector plus one for Mount Nienokoue, using information of three soil pits per catena. A SPOT satellite image from 1998 has been treated to map the zones with degraded forest vegetation. · • 930 plant species have been identified on the sample plots and along the transects. Combined w...