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.

Tree species diversity in Kalidhar forest of western Shiwaliks, Jammu, JK (UT)

The present study was conducted in Kalidhar forest of western Shiwaliks, Jammu, JK (UT), to assess the tree diversity and undertake phytosociological analysis in three major land use (LU) classes i.e. Forest, Agriculture and Scrub area. A total of 70, 50 and 50 sample plots of 0.1 ha were laid respectively in forests, scrub and agriculture LU classes. The study revealed that in forests possess a total 39 tree species belonging to 19 families and 31 genera, whereas, in scrub and agriculture lands a total of 9 tree species (8 families and 9 genera) and 60 tree species (26 families and 46 genera) were recorded respectively. Mallotus philippensis was the most dense tree species with 2.85 individuals per ha in forests followed by Pinus roxburghii 2.06 per hectare. In scrub and agriculture land Acacia modesta and Grewia optiva were found the densest species respectively. The value of Importance value index (IVI) was found highest for Pinus roxburhii (44.63) in forests, whereas, respective values were recorded highest for Syzygium cumini (82.64) and Grewia optiva (29.0) in scrub and agriculture lands. Flacourtia indica and Pinus roxburghii showed random distribution in forest and Syzygium cumini was also found to have random distribution in the scrub lands. Contiguous distribution was found for all tree species encountered in agriculture (LU) class. The diversity values of Shannon Wiener and Simpson indices showed highest tree diversity in agriculture lands with the values of 3.19 and 0.07 respectively followed by that in forests (2.47 and 0.14). Tree species richness was found high in agriculture area with Margalef’s (59.86) and Menhinick’s (1.80).

Tree Species Diversity and Abundance of Akure Forest Reserve, Ondo State, Nigeria

This study was carried out to examine the tree species diversity and abundance in a natural forest ecosystem in the Southwestern region of Nigeria. Data were collected from a four equal size sampling plot of 50×50m in a permanent sample plot section of Akure Forest Reserve. All living trees with DBH ≥ 10cm were measured and identified. A total of 956 trees were encountered. These trees were from 42 genera and 20 families. Celtis zenkeri belonging to the family of Ulmaceae was the species with the highest population distribution while Sterculiaceae was the dominant family in the study area. The Shannon-Wiener Diversity Index (Hˈ) of 3.196 and species evenness of 0.84 were obtained from the study area. The high values of diversity indices obtained indicated that the forest is rich in biodiversity and hence should be protected from any forms of disturbance to enhance sustainability as well as protect the rare species in it from going into extinction.

Forest health study in efforts to preserve community forest agroforestry patterns in Kubu Batu Village, Gedong Tataan District, Pesawaran Regency, Lampung Province

The agroforestry pattern community forest in Kubu Batu Village, Gedong Tataan District, Pesawaran Regency, Lampung Province has essential values for the community, both economically, ecologically, and socially. Therefore, to ensure the sustainability of the community forest, a forest health assessment is carried out. Forest health assessment is one of the criteria for achieving community forest sustainability. This study aims to determine the condition (status) and ecological factors that affect the health level of community forests using agroforestry patterns in Kubu Batu Village, Gedong Tataan District, Pesawaran Regency, Lampung Province. The research methods used are the Forest Health Monitoring method to measure forest health with the Forest Health Assessment Information System (SIPUT) and sperm rank correlation to determine the relationship between ecological factors and the health level community forests using agroforestry patterns. The results showed the condition (status) of community forest health in agroforestry patterns with good categories in cluster plots 2, 4, 5, and 6, moderate categories in cluster plots 1 and 7, and bad categories in cluster plots 3. Strongly positive/unidirectional agroforestry patterns are the crown condition and tree species diversity. This condition illustrates that it preserves community forests using agroforestry patterns in Kubu Batu Village is necessary to focus tree species diversity attention on tree crown parameters. Thus, the health status of community forest agroforestry patterns in Kubu Batu Village is good. This proves that the people there have made efforts to maintain the sustainability of their community forests.

Aboveground Biomass of Living Trees Depends on Topographic Conditions and Tree Diversity in Temperate Montane Forests from the Slătioara-Rarău Area (Romania)

The study zone includes one of the largest montane old-growth forests in Europe (Slatioara UNESCO site), and understanding the structure and functioning of sill intact forests in Europe is essential for grounding management strategies for secondary forests. For this reason, we set out to analyze the dependencies between aboveground biomass (AgB), tree species and size diversity and terrain morphology, as well as the relationship between biomass and diversity, since neither of these issues have been sufficiently explored. We found that tree species diversity decreases with increased solar radiation and elevation. Tree size heterogeneity reaches its highest mean values at elevations between 1001 and 1100 m, on slopes between 50 and 60 degrees. AgB is differentiated with elevation; the highest mean AgB (293 tonnes per hectare) is recorded at elevations between 801 and 900 m, while it decreases to 79 tonnes per hectare at more than 1500 m a.s.l. It is also influenced by tree species diversity and tree size heterogeneity, with the highest AgB reached in the most complex forest ecosystems in terms of structural diversity. We showed that intact temperate montane forests develop maximum biomass for optimum species diversity and highest size heterogeneity; all three are modulated mainly by elevation.

A Combination of Biotic and Abiotic Factors and Diversity Determine Productivity in Natural Deciduous Forests

The relative importance of different biotic and abiotic variables for estimating forest productivity remains unclear for many forest ecosystems around the world, and it is hypothesized that forest productivity could also be estimated by local biodiversity factors. Using a large dataset from 258 forest monitoring permanent sample plots distributed across uneven-aged and mixed forests in northern Iran, we tested the relationship between tree species diversity and forest productivity and examined whether several factors (solar radiation, topographic wetness index, wind velocity, seasonal air temperature, basal area, tree density, basal area in largest trees) had an effect on productivity. In our study, productivity was defined as the mean annual increment of the stem volume of a forest stand in m3 ha−1 year−1. Plot estimates of tree volume growth were based on averaged plot measurements of volume increment over a 9-year growing period. We investigated relationships between productivity and tree species diversity using parametric models and two artificial neural network models, namely the multilayer perceptron (MLP) and radial basis function networks. The artificial neural network (ANN) of the MLP type had good ability in prediction and estimation of productivity in our forests. With respect to species richness, Model 4, which had 10 inputs, 6 hidden layers and 1 output, had the highest R2 (0.94) and the lowest RMSE (0.75) and was selected as the best species richness predictor model. With respect to forest productivity, MLP Model 2 with 10 inputs, 12 hidden layers and 1 output had R2 and RMSE of 0.34 and 0.42, respectively, representing the best model. Both of these used a logistic function. According to a sensitivity analysis, diversity had significant and positive effects on productivity in species-rich broadleaved forests (approximately 31%), and the effects of biotic and abiotic factors were also important (29% and 40%, respectively). The artificial neural network based on the MLP was found to be superior for modeling productivity–diversity relationships.