Quantifying Arborescent Flora Diversity in a Secondary Forest Ecosystem: A Comprehensive Assessment in Nambalan, Mayantoc, Tarlac, Philippines

Forest plays a crucial role in providing essential ecosystem services, including water supply, climate regulation, and biodiversity conservation. This study aimed to assess the current state of the forest in Barangay Nambalan, Mayantoc, Tarlac. The specific objectives were to identify tree species in the area and determine the tree diversity index, with a focus on endemism and conservation status. Two transect lines, each spanning one kilometer, were established and a total of 10 sampling quadrats were surveyed. Ecological parameters (relative frequency, relative density, relative dominance, and importance value index) and diversity indices (Shannon-Weiner index, Simpson’s index) were computed using the Paleontological Statistic Software Package for Educational Analysis (PAST 4.03). A comprehensive inventory revealed a total of 756 individuals representing 52 species, 46 genera, and 25 families. Among the recorded species, 10 (17.2%) were endemic and 11 (21.6%) were classified as threatened. The Fabaceae (20.8%), Moraceae (14.6%), and Euphorbiaceae (8.3%) were identified as the most abundant families. The computed diversity indices indicated that Barangay Nambalan retains a diverse forest cover;however, species composition was found to be relatively low. Based on the finding, this study recommends the strict enforcement of protective measures and legislation to mitigate further degradation of the remaining forest in Barangay Nambalan.

Large-scale forest inventories of the United States and China reveal positive effects of biodiversity on productivity

Background： With the loss of species worldwide due to anthropogenic factors, especially in forested ecosystems, it has become more urgent than ever to understand the biodiversity-ecosystem functioning relationship （BEFR）. BEFR research in forested ecosystems is very limited and thus studies that incorporate greater geographic coverage and structural complexity are needed. Methods： We compiled ground-measured data from approx, one half million forest inventory sample plots across the contiguous United States, Alaska, and northeastern China to map tree species richness, forest stocking, and productivity at a continental scale. Based on these data, we investigated the relationship between forest productivity and tree species diversity, using a multiple regression analysis and a non-parametric approach to account for spatial autocorrelation. Results： In general, forests in the eastern United States consisted of more tree species than any other regions in the country. The highest forest stocking values over the entire study area were concentrated in the western United States and Central Appalachia. Overall, 96.4 % of sample plots （477,281） showed a significant positive effect of species richness on site productivity, and only 3.6 % （17,349） had an insignificant or negative effect. Conclusions： The large number of ground-measured plots, as well as the magnitude of geographic scale, rendered overwhelming evidence in support of a positive BEFR. This empirical evidence provides insights to forest management and biological conservation across different types of forested ecosystems. Forest timber productivity may be impaired by the loss of species in forests, and biological conservation, due to its potential benefits on maintaining species richness and productivity, can have profound impacts on the functioning and services of forested ecosystems.

Effects of patch size, disturbances on diversity and structural traits of tropical semi-evergreen forest in the lowland Indo Burma hotspot: implication on conservation of the threatened tree species

Information on geographic distribution, population and threat status of most globally red listed species in the Indo Burma zone are inadequate. Given the increase in the prevalence of isolated forest patches in the part of this hotspot, evaluation is necessary on how size of the remnant forest patches and on-going disturbances affects structure and diversity of remaining habitats including the population of some globally threatened tree species. Quantitative vegetation inventory by 500 m long and lO m wide （0.5 ha） line transects were randomly set in nine fragmented tropical semi-evergreen forest patches in Tripura, Northeast India. The studied forests patches grouped into small, medium and large based on their respected sizes. Spatial variability was analysed in woody species diversity and structure along the patch size gradients and their response to both patch size and anthropogenic disturbances. Out of 167 species, 13 identified as red-listed species by IUCN under the present inventory. Most of the diversity and structural parameters showed statistically significant positive response with the forest patch size, except for stand dominance, disturbance, sapling density and number of aggregated distribution pattern decreased when patch size increased. In addition, most of the diversity and structural attributes showed negative response with disturbances. Present baseline data would serve as an effective tool for management and protection of this important forest type. Future habitat restoration programme and strategies for relocation of additional population and re-introduction of those globally threatened trees are recommended.

Species Richness, Diversity and Density of Understory Vegetation along Disturbance Gradients in the Himalayan Conifer Forest

We investigated whether species richness, diversity and density of understory herbaceous plants differed along logging(gap) and grazing(primarily by cattle) disturbance gradients, and sought to identify drivers of richness, diversity and density of understory vegetation of logged sites. A factorial experiment was conducted in the mixed conifer forest of Gidakom in Western Bhutan. Levels of the logging treatment included small(0.15 – 0.24 ha), medium(0.25 – 0.35 ha) and large(0.36 – 1.31 ha) gaps. The grazing treatment included grazed(primarily by cattle) and ungrazed(where herbivores were excluded by a fence) plots nested within each gap. Data were collected from 12 gaps(4 replicates at each level of logging) using the point intercept method. Shannon Weaver Diversity and Margalef's indices were used to estimate species diversity and describe species richness, respectively. Soil samples were analyzed for pH and nutrients. The interaction effect of logging and grazing was significant(p≤0.001) only on species diversity. Relative to ungrazed areas, species diversity was significantly higher(0.01≤p≤0.05) in medium grazed gaps. Under grazed conditions, soil P was negatively correlated with gap size and species diversity. While species diversity was positivelycorrelated(0.01≤p≤0.05) with soil N in grazed plots species richness was positively correlated(0.001≤p≤0.01) with soil N in ungrazed plots. Relative density of Yushania microphylla and Carex nubigena were higher under ungrazed conditions. Our study suggests that the combined effect of cattle grazing and logging results in higher species diversity of understory vegetation in medium and grazed gaps in mixed conifer forests of Bhutan,whereas increase or decrease in relative density of major species is determined primarily by the independent effects of grazing and logging. From management perspective, forest managers must refrain from creating large gaps to avoid loss of nutrients(mainly P and N), which may eventually affect tree regeneration. Managers intending to maintain understory vegetation diversity must consider the combined effects of grazing and logging, ensuring low to moderate grazing pressure.

The rapid climate change-caused dichotomy on subtropical evergreen broad-leaved forest in Yunnan： Reduction in habitat diversity and increase in species diversity

Yunnan's biodiversity is under considerable pressure and subtropical evergreen broad-leaved forests in this area have become increasingly fragmented through agriculture,logging,planting of economic plants,mining activities and changing environment.The aims of the study are to investigate climate changeinduced changes of subtropical evergreen broad-leaved forests in Yunnan and identify areas of current species richness centers for conservation preparation.Stacked species distribution models were created to generate ensemble forecasting of species distributions,alpha diversity and beta diversity for Yunnan's subtropical evergreen broad-leaved forests in both current and future climate scenarios.Under stacked species distribution models in rapid climate changes scenarios,changes of water-energy dynamics may possibly reduce beta diversity and increase alpha diversity.This point provides insight for future conservation of evergreen broad-leaved forest in Yunnan,highlighting the need to fully consider the problem of vegetation homogenization caused by transformation of water-energy dynamics.

Diversity of insect communities with different development phases in natural Populus euphratica forests in Xinjiang

An investigation method with sample plots was used to study insect communities in four different growth phases of natural Populus euphratica forests, which are juvenile, middle aged, over-mature and degraded forests, in Tarim, Xinjiang in July, 2005 and April, 2006. In our studies, 5,116 insect specimens, belonging to 12 orders, 61 families and 141 species, were collected. Lepidoptera and Coleoptera were the dominant orders. In middle-aged forests, species, individual numbers and diversity indices of insect com-munities were higher than those in other woodlands. The species richness and diversity indices were lowest in degraded forests be-cause of extremely scarce vegetation.

Effects of grazing on natural regeneration of tree and herb species of Kheyroud forest in northern Iran

We investigated the effects of grazing on natural regeneration, quantity, and diversity of woody species and dominant herb species in Kheyroud forest in northern Iran. We sampled vegetation in 5m2 plots in custom units, which are demarcated resource areas traditionally used by local livestock producers. The authors quantified number of species, height of seedlings, and diameter of seedlings. Height classes were 0-30 cm, 30-130 cm, and 〉130 cm, and diameter classes were 0-2.5 cm, 2.5-5 cm and 5-7.5 cm. The density of seedlings declined with distance from corral until reaching the custom unit boundary. Most seedlings had diameters of 0-2.5 cm and heights of 0-30 cm. Predominant species, Carpinus betulus and Acer capadocicum, were in plots near the centers of custom units, Fagus orientalis, Acer velutinum, Quercus castanifolia species were dominant in plots near the custom unit boundary. Plant species such as Oplismenus undulatifolius, Euphorbia amygdaloides, Rubusfrutieos and Pteridium aquilinum were dominant in plots nearer to forest corral. Healthy seedlings were more numerous in plots nearest the corral, while defective and deformed seedlings were more abundant away from the corral. We conclude that grazing had negative effects on the quantity and quality of vegetative regeneration. Continuation of overgrazing will not only endanger the sustainability of forest ecosystems, but also will increase the challenge of sustainable forest management.

Demographic variation and habitat specialization of tree species in a diverse tropical forest of Cameroon

Background： Many tree species in tropical forests have distributions tracking local ridge-slope-valley topography. Previous work in a 50-ha plot in Korup National Park, Cameroon, demonstrated that 272 species, or 63% of those tested, were significantly associated with topography. Methods： We used two censuses of 329,000 trees ≥1 cm dbh to examine demographic variation at this site that would account for those observed habitat preferences. We tested two predictions. First, within a given topographic habitat, species specializing on that habitat （＇residents＇） should outperform species that are specialists of other habitats （＇foreigners＇）. Second, across different topographic habitats, species should perform best in the habitat on which they specialize （＇home＇） compared to other habitats （＇away＇）. Species＇ performance was estimated using growth and mortality rates. Results： In hierarchical models with species identity as a random effect, we found no evidence of a demographic advantage to resident species. Indeed, growth rates were most often higher for foreign species. Similarly, comparisons of species on their home vs. away habitats revealed no sign of a performance advantage on the home habitat. Conclusions＂ We reject the hypothesis that species distributions along a ridge-valley catena at Korup are caused by species differences in trees _〉1 cm dbh. Since there must be a demographic cause for habitat specialization, we offer three alternatives. First, the demographic advantage specialists have at home occurs at the reproductive or seedling stage, in sizes smaller than we census in the forest plot. Second, species may have higher performance on their preferred habitat when density is low, but when population builds up, there are negative density-dependent feedbacks that reduce performance. Third, demographic filtering may be produced by extreme environmental conditions that we did not observe during the census interval.