Differences in Tree Species Diversity and Soil Nutrient Status in a Tropical Sacred Forest Ecosystem on Niyamgiri Hill Range,Eastern Ghats,India

We have quantitatively analyzed the tree species diversity with respect to soil nutrient status in three sites of a sacred forest ecosystem of Niyamgiri hill range, Eastern Ghats, India. Extensive field surveys and sampling were conducted in 3 sites of the hill range： Site 1 Pterocarpus dominated forest （PTF） （19°40＇02.2＇＇ N and 83°21＇23.1＇＇ E）, Site 2 Mangifera dominated forest （MAF） （19°40＇02.8＇＇ N and 83°21＇40.8＇＇ E） and Site 3 Mixed forest （MIF） （19°36＇47.1＂ N and 83°21＇02.7＇＇ E）. A total of 28 families, 42 genera, 46 tree species, and 286 individual trees were recorded on an area of0.6 ha. Tree density varied between 470 and 49o individuals ha and average basal area between 3.16 and l0.04 m2 ha-1. Shannon Index （H＇） ranged from 2.34 to 4.53, Simpson＇s Index ranged from 0.07 to o.09, and equitability Index ranged from 0.7 to 1.34. The number of individuals was highest in the girth at breast height （GBH） class of 50-7o cm. The soil nutrient status of the three forest types was related to tree species diversity. The soil pH value of the three sites reflected the slightly acidic nature of the area. Species diversity was positively correlated with organic carbon and phosphorus and negatively with nitrogen, EC and pH. The results of the current study may be helpful to further develop a conservation planfor tree species in tropical sacred forest ecosystems.

Some of the Mechanisms for Coexistence of Tree Species Diversity in Tropical Forests: A Review of Effects of Tree Density Dependence

Tree communities contribute to maintenance of species diversity in tropical forests. Coexistence of many tree species is not without competition. Therefore, coexistence of tree species and size diversities occur sequentially or simultaneously in tropical natural forests. Understanding coexistence and competition mechanisms of tree species requires knowledge of interactions within and between species. However, many conservation efforts and strategies failed due to inability to identify and maintain functional coexistence mechanisms among tree species in the forest. Also, most trees died because of pressure on their habitats and not because of limiting growth resources. Hence, species identity, minimum distance and size of the neighbouring trees which are responsible for coexistence of competing trees in most tropical forests have not been explicitly reviewed. Therefore, this review evaluated some of the density dependent mechanisms for coexistence of tree species alpha diversity in tropical forests. Many interactive mechanisms are responsible for coexistence tree species in tropical forests. Inter- and intra-specific competitions are the most significant and both facilitate positive and negative density dependence. Therefore, switching from negative to positive density dependence may occur in some situations. Positive and negative density effects regulate species abundance and coexistence through conspecific and heterospecific structures. Aggregates of conspecific and heterospecific neighbours constitute forest spatial structure. Negative density interactions are mutually exclusive and basically ranged from effect of species identity of neighbours, distance to neighbours and tree size of the neighbours to reference trees in the community structures. Some mechanisms shorten distances for heterospecific than conspecific interactions. Conspecific structures improved survival and growth of rare tree species. Interactive mechanisms in tree community and population structures facilitate species diversity and size inequality, respectively.

The coordinated impact of forest internal structural complexity and tree species diversity on forest productivity across forest biomes

Forest structural complexity can mediate the light and water distribution within forest canopies,and has a direct impact on forest biodiversity and carbon storage capability.It is believed that increases in forest structural complexity can enhance tree species diversity and forest productivity,but inconsistent relationships among them have been reported.Here,we quantified forest structural complexity in three aspects(i.e.,horizontal,vertical,and internal structural complexity)from unmanned aerial vehicle light detection and ranging data,and investigated their correlations with tree species diversity and forest productivity by incorporating field measurements in three forest biomes with large latitude gradients in China.Our results show that internal structural complexity had a stronger correlation(correlation coefficient=0.85)with tree species richness than horizontal structural complexity(correlation coefficient=-0.16)and vertical structural complexity(correlation coefficient=0.61),and it was the only forest structural complexity attribute having significant correlations with both tree species richness and tree species evenness.A strong scale effect was observed in the correlations among forest structural complexity,tree species diversity,and forest productivity.Moreover,forest internal structural complexity had a tight positive coordinated contribution with tree species diversity to forest productivity through structure equation model analysis,while horizontal and vertical structural complexity attributes have insignificant or weaker coordinated effects than internal structural complexity,which indicated that the neglect of forest internal structural complexity might partially lead to the current inconsistent observations among forest structural complexity,tree species diversity,and forest productivity.The results of this study can provide a new angle to understand the observed inconsistent correlations among forest structural complexity,tree species diversity,and forest productivity.

The effect of microclimate on wood decay is indirectly altered by tree species diversity in a litterbag study

Aims We studied the influence of tree species diversity on the dynamics of coarse wood decomposition in developing forest communities in a natural,topographically heterogeneous landscape.Using the litter bag technique,we investigated how and to which extent canopy tree species richness or the exclusion of mesoinvertebrates and macroinvertebrates affected wood decomposition in the light of natural variations in the microclimate.We compared the relative importance of the two aspects(experimental treatment versus microclimate)on wood decay rates using Schima superba as a standard litter.Methods Coarse woody debris(CWD)was deposited in litter bags with two different mesh sizes in a total of 134 plots along a gradient of canopy tree species richness(0-24 species).Wood decomposition was assessed at two consecutive time points,one and three years after deposition in the field.Local climatic conditions were assessed throughout the duration of the experiment.Microclimatic conditions were assessed both,directly in the field as well as indirectly via correlations with local topography.We used analysis of variance based approaches to assess the relative importance of the treatments(community tree species richness and macro invertebrate exclusion)and microclimatic conditions on wood decay.Important Findings No direct influence of tree species richness on wood decay could be detected.However,the exclusion of macroinvertebrates significantly decreased wood decomposition rates.In addition,microclimatic conditions accounted for a substantial proportion of explained variance in the observed data.Here,wood decomposition was negatively affected by low mean temperatures and high variations in local humidity and temperature.However,tree species richness as well as the respective species composition affected the presence of termites within forest communities.These,in turn,significantly increased the decay of CWD.The strength of both,experimental treatment and microclimate increased with ongoing decomposition.We conclude that,while tree species richness per se has no direct influence on wood decomposition,its influence on the local arthropod decomposer community(especially the presence of termites)does have an effect.

N-fixing tree species promote the chemical stability of soil organic carbon in subtropical plantations through increasing the relative contribution of plant-derived lipids

Biodiversity experiments have shown that soil organic carbon(SOC)is not only a function of plant diversity,but is also closely related to the nitrogen(N)-fixing plants.However,the effect of N-fixing trees on SOC chemical stability is still little known,especially with the compounding effects of tree species diversity.An experimental field manipulation was established in subtropical plantations of southern China to explore the impacts of tree species richness(i.e.,one,two,four and six tree species)and with/without N-fixing trees on SOC chemical stability,as indicated by the ratio of easily oxidized organic carbon to SOC(EOC/SOC).Plant-derived C components in terms of hydrolysable plant lipids and lignin phenols were isolated from soils for evaluating their relative contributions to SOC chemical stability.The results showed that N-fixing tree species rather than tree species richness had a significant effect on EOC/SOC.Hydrolysable plant lipids and lignin phenols were negatively correlated with EOC/SOC,while hydrolysable plant lipids contributed more to EOC/SOC than lignin phenols,especially in the occurrence of N-fixing trees.The presence of N-fixing tree species led to an increase in soil N availability and a decrease in fungal abundance,promoting the selective retention of certain key components of hydrolysable plant lipids,thus enhancing SOC chemical stability.These findings underpin the crucial role of N-fixing trees in shaping SOC chemical stability,and therefore,preferential selection of N-fixing tree species in mixed plantations is an appropriate silvicultural strategy to improve SOC chemical stability in subtropical plantations.

Remote sensing of subtropical tree diversity:The underappreciated roles of the practical definition of forest canopy and phenological variation

Tree species diversity is vital for maintaining ecosystem functions,yet our ability to map the distribution of tree diversity is limited due to difficulties in traditional field-based approaches.Recent developments in spaceborne remote sensing provide unprecedented opportunities to map and monitor tree diversity more efficiently.Here we built partial least squares regression models using the multispectral surface reflectance acquired by Sentinel-2 satellites and the inventory data from 74 subtropical forest plots to predict canopy tree diversity in a national natural reserve in eastern China.In particular,we evaluated the underappreciated roles of the practical definition of forest canopy and phenological variation in predicting tree diversity by testing three different definitions of canopy trees and comparing models built using satellite imagery of different seasons.Our best models explained 42%–63%variations in observed diversities in cross-validation tests,with higher explanation power for diversity indices that are more sensitive to abundant species.The models built using imageries from early spring and late autumn showed consistently better fits than those built using data from other seasons,highlighting the significant role of transitional phenology in remotely sensing plant diversity.Our results suggested that the cumulative diameter(60%–80%)of the biggest trees is a better way to define the canopy layer than using the subjective fixeddiameter-threshold(5–12 cm)or the cumulative basal area(90%–95%)of the biggest trees.Remarkably,these approaches resulted in contrasting diversity maps that call attention to canopy structure in remote sensing of tree diversity.This study demonstrates the potential of mapping and monitoring tree diversity using the Sentinal-2 data in species-rich forests.

Assessment of Tree Diversity and Abundance in Rashad Natural Reserved Forest, South Kordofan, Sudan

This study aims to estimate the tree diversity status of Rashad Forest Reserves in the Rashad locality of the South Kordofan State of Sudan. For data collection, eight sample plots (20 × 20 m) were taken randomly, and parameters were determined: trees species diversity, composition, relative density, dominance, important value index, and species richness in the Rashad forest reserve. The results show that a total of 237 and 56 tree species, including 22 families, have been identified in the study area. Fabaceae family and species numbers have the highest number of 13 species in 8 genera, followed by Combretaceae with 8 species belonging to 3 different genera, Malvaceae with 5 species belonging to 4 different genera, Apocynaceae with 3 species belonging to 3 different genera. The Arecaceae, Burseraceae, Capparaceae, Euphorbiaceae, Meliaceae, and Rubiaceae families each had two species, and all the other 11 families had one species each. Among the 56 different tree species found within the reserve. The results also indicated that Tamarindus indica L. and Ziziphus spina-christi (L.) Desf. had the highest relative density and dominance of 4.64% and 11% respectively. Adansonia digitata L., Grewia villosa Willd, Vepris nobilis (Delile) Mziray had density and dominance of 4.80% and 9%. Followed by Anogeissus leiocarpa (DC.) Guill. & Perr, Adansonia digitata L., Catunaregam nilotica (Stapf) Tirveng. (Syn: Xeromphis nilotica (Stapf) Keay, Vangueria madagascariensis J. F. Gmel. with 3.38% and 8%, respectively. Eleven species recorded the least relative dominance of 0.42%. Shannon-Weiner diversity index (H’) value stood at 3.82. And as diversity indices varied with location depending on the species available within an ecological zone, Rashad forest reserve is blessed with a moderate diversity index.

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.

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.