Tree regeneration characteristics in limestone forests of the Cat Ba National Park, Vietnam

Background The ability of overstory tree species to regenerate successfully is important for the preservation of tree species diversity and its associated flora and fauna. This study investigated forest regeneration dynamics in the Cat Ba National Park, a biodiversity hotspot in Vietnam. Data was collected from 90 sample plots (500 m2) and 450 sub-sample plots (25 m2) in regional limestone forests. We evaluated the regeneration status of tree species by developing five ratios relating overstory and regeneration richness and diversity. By examining the effect of environmental factors on these ratios, we aimed to identify the main drivers for maintaining tree species diversity or for potential diversity gaps between the regeneration and the overstory layer. Our results can help to increase the understanding of regeneration patterns in tropical forests of Southeast Asia and to develop successful conservation strategies. Results We found 97 tree species in the regeneration layer compared to 136 species in the overstory layer. The average regeneration density was 3764 ± 1601 per ha. Around 70% of the overstory tree species generated offspring. According to the International Union for Conservation of Nature’s Red List, only 36% of threatened tree species were found in the regeneration layer. A principal component analysis provided evidence that the regeneration of tree species was slightly negatively correlated to terrain factors (percentage of rock surface, slope) and soil properties (cation exchange capacity, pH, humus content, soil moisture, soil depth). Contrary to our expectations, traces of human impact and the prevailing light conditions (total site factor, gap fraction, openness, indirect site factor, direct site factor) had no influence on regeneration density and composition, probably due to the small gradient in light availability. Conclusion We conclude that the tree species richness in Cat Ba National Park appears to be declining at present. We suggest similar investigations in other biodiversity hotspots to learn whether the observed trend is a global phenomenon. In any case, a conservation strategy for the threatened tree species in the Cat Ba National Park needs to be developed if tree species diversity is to be maintained.

Pre-Sowing Treatments Accelerate Germination Percent for Restoration of Fourteen Threatened Tree Species in Bangladesh

Ecologically valuable native tree species are becoming threatened due to deforestation, forest fragmentation and preference of fast-growing exotics than the native ones in plantation. One of the main reasons for the preference of exotic species than the native ones is its higher rate of germination and rapid growth. The effect of different pre-sowing treatments was studied on fourteen threatened tree species of Bangladesh to find out the appropriate treatments for speed up germination rate and initial seedling growth. These species are ecologically valuable multipurpose indigenous trees of Bangladesh. Methanol extract of Castanopsis indica leaves could decrease the tumor Ehrlich Ascites Carcinoma volume and weight. Lophopetalum wightianum is a globally threatened tree species. Hard coated seeds of Canarium resiniferum, Castanopsis indica, Protium serratum, Quercus acuminata and Vitex peduncularis were treated with sand paper, nicking, normal water, hot water, H2SO4 and HCl. Soft coated seeds of Brownlowia elata, Dichopsis polyantha, Firmiana colorata, Lophopetalum wightianum, Pterospermum acerifolium, Pterospermum semisagittatum, Pterygota alata, Schleichera oleosa and Sterculia villosa were sown in polybags, propagator house and nursery bed in normal, flat and 45o angle positions. Among all hard-coated seeds, Castanopsis indica showed significantly higher germination percentage (67%) after seeds treated with sandpaper in comparison to control (25%). Soft-coated seeds of Lophopetalum wightianum showed significantly higher germination percentage (90%) among all studied species when sown in propagator house, whereas in natural condition it provides only 26% germination rate. This paper will help to restore ecologically valuable threatened species.

Phytotherapy and Polycyclic Logging: Implication on Genetic Multiplicity and Diversity of African Mahogany in Tropical Rainforest

There are over 8,000 globally threatened tree species. For each species, there is a different story behind why they are threatened and what values we stand to lose if we do not find the means to save them. Mahogany, a member of Meliaceae, is a small genus with six species. Its straight, fine and even grain, consistency in density and hardness makes it a high valued wood for construction purposes. The bitter bark is widely used in traditional medicine in Africa. The high demand for bark has also led to the total stripping of some trees, complete felling of larger trees to get the bark from the entire length of the tree and bark removal from juvenile trees. These species are now threatened with extinction due to selective and polycyclic logging, and also excessive bark removal. The natural regeneration of mahogany is poor, and mahogany shoot borer Hypsipyla robusta (Moore) attacks prevent the success of plantations within the native area in West Africa. In developing countries, most of the Khaya species exists in the wild state; therefore, the regeneration and long-term conservation are at the mercy of the vagaries of nature and the profit driven herb collectors and timber merchants. It becomes urgently necessary by government of developing countries to place ban on further harvesting of mahogany species to allow the remaining few trees of mahogany in the forest to recuperate and produce substantial seeds for regeneration.