Using phytocoenological and phytodemographic methods , we studied the quantitative and qualitative characteristics of plant species diversity of tropical natural forest in Bawangling , Hainan Island. The results showed that 1) plant communities of this area had great differences in the composition of dominant speciesand there were low species similarities among the communities ; 2) the mountain rain forest in this area had alarger number of species , a higher level of species evenness and relatively weaker dominance of the species thanthe lowland rain forest ; 3) setting priority according to species rarity , all the plants in this area can be dividedinto three categories according to their positions and distributions in the communities , namely rare and endangered species , characteristic species , and common species , and 4) some suggestions were put forward for theconservation of plant species diversity in this area.

Using phytocoenological and phytodemographic methods , we studied the quantitative and qualitative characteristics of plant species diversity of tropical natural forest in Bawangling , Hainan Island. The results showed that 1) plant communities of this area had great differences in the composition of dominant speciesand there were low species similarities among the communities ; 2) the mountain rain forest in this area had alarger number of species , a higher level of species evenness and relatively weaker dominance of the species thanthe lowland rain forest ; 3) setting priority according to species rarity , all the plants in this area can be dividedinto three categories according to their positions and distributions in the communities , namely rare and endangered species , characteristic species , and common species , and 4) some suggestions were put forward for theconservation of plant species diversity in this area.

Based on field investigation data and employing Levin and niche proportional similarity formulae, this paper calculated the niche breadth, niche proportional similarity, and niche overlap of 13 dominant species of Sophora davidii community in loess gully region. The results showed that the niche breadth of the dominant populations of Sophora davidii community decreased in order of Sophora davidii (0.964), Artemisia giraldii (0.775), Arteniisia gmelinii (0.664), Thenmeda triandra var. japonica (0.508), Polygala tenuifolia (0.485), Setaria viridis (0.399), Cynodon dactylon (0.393), Bothriochloa ischaemum (0.327), Lespedeza davurica (0.321), Stipa bungeana (0.472), Periploca sepium (0.292), Clemnatis fruticosa (0.251), and Cleistogenes squarrosa (0.234). The niche proportional similarity between Sophora davidii and other species was 0.21-0.76, while the niche overlap was not high, which meant that there was no severe competition between them. It could be concluded that Sophora davidii was the dominant population in the community, with most resources utilization and most adaptability to the ecosystem.

Based on field investigation data and employing Levin and niche proportional similarity formulae, this paper calculated the niche breadth, niche proportional similarity, and niche overlap of 13 dominant species of Sophora davidii community in loess gully region. The results showed that the niche breadth of the dominant populations of Sophora davidii community decreased in order of Sophora davidii (0.964), Artemisia giraldii (0.775), Arteniisia gmelinii (0.664), Thenmeda triandra var. japonica (0.508), Polygala tenuifolia (0.485), Setaria viridis (0.399), Cynodon dactylon (0.393), Bothriochloa ischaemum (0.327), Lespedeza davurica (0.321), Stipa bungeana (0.472), Periploca sepium (0.292), Clemnatis fruticosa (0.251), and Cleistogenes squarrosa (0.234). The niche proportional similarity between Sophora davidii and other species was 0.21-0.76, while the niche overlap was not high, which meant that there was no severe competition between them. It could be concluded that Sophora davidii was the dominant population in the community, with most resources utilization and most adaptability to the ecosystem.

A total of one hundred and twelve 10 m×10 m quadrats were set up in ten terrestrial
secondary forest communities of Zhuhai City, Guangdong Province to study the niche breadth and
niche overlap of the dominant plant species. The results indicated that the Shannon-Wiener’s niche
breadth and Levins’s niche breadth of 23 dominant species in the communities were 0.4049—0.7736
and 0.0551—0.3086, respectively. The species with larger niche breadth were Acronychia pedunculata,
Gordonia axillaris, Aporosa dioica, Microdesmis casearifolia, Gironniera subaequalis, and Sterculia lanceolata,
which were the widespread species in natural forests. The niche similarity of dominant species varied
between 0 and 0.3810, and the highest one occurred between A. dioica and Cinnamomum burmanii.
A. pedunculata had different degree niche overlaps with other 22 species, but G. axillaris only had niche
overlaps with a few dominant species. There were no niche overlaps in 20.6% of species-pairs. It was
suggested that some widespread and well-adapted species with larger niche breadth, e . g . , A. pedunculata,
G. axillaris, G. subaequalis and Endospermum chinense, should be selected in prior in the restoration of
natural forests and the reconstruction of plantations.

A total of one hundred and twelve 10 m×10 m quadrats were set up in ten terrestrial
secondary forest communities of Zhuhai City, Guangdong Province to study the niche breadth and
niche overlap of the dominant plant species. The results indicated that the Shannon-Wiener’s niche
breadth and Levins’s niche breadth of 23 dominant species in the communities were 0.4049—0.7736
and 0.0551—0.3086, respectively. The species with larger niche breadth were Acronychia pedunculata,
Gordonia axillaris, Aporosa dioica, Microdesmis casearifolia, Gironniera subaequalis, and Sterculia lanceolata,
which were the widespread species in natural forests. The niche similarity of dominant species varied
between 0 and 0.3810, and the highest one occurred between A. dioica and Cinnamomum burmanii.
A. pedunculata had different degree niche overlaps with other 22 species, but G. axillaris only had niche
overlaps with a few dominant species. There were no niche overlaps in 20.6% of species-pairs. It was
suggested that some widespread and well-adapted species with larger niche breadth, e . g . , A. pedunculata,
G. axillaris, G. subaequalis and Endospermum chinense, should be selected in prior in the restoration of
natural forests and the reconstruction of plantations.

Analyses of species diversity and endemism patterns provide vital inputs for conservation planning. Therefore, it is an important dilemma of biodiversity conservation that in very diverse but poorly studied tropical countries those patterns can hardly be considered. Consequently, there is an urgent need to develop prediction models that make the best use of existing data on species distribution and that can give hints on spatial conservation priorities. This paper presents the results of a pilot study on the diversity of the orchid subtribe Pleurothallidinae (331 mapped species) in the Andean rain forests of Bolivia. Results of a taxon-based mapping methodology, using abiotic (humidity and temperature, the latter indicated by altitude) and historical factors (taken into account as distance from collection localities) that determine species ranges, are compared with outcomes of an inventory-based mapping approach. The patterns of taxon-based diversity and endemism show a strong correlation with the distribution of sample localities. The inventory-based approach is more reliable, but it is interesting to apply both mapping methods in order to make a critical interpretation and comparison that facilitates some valuable conservation recommendations. We end with concrete conclusions for conservation planning and action.

Based on the data collected from the plots investigation along with the implementation Levins, Shannon weiner index and niche overlap formulas in Mt. Qinling Shaanxi, the niche breadth values, niche similarity and niche overlap values of the main tree species were measured in the forestry of Abies chensiensis in this study. The results showed that: with the respective Levins and Shannon weiner index, the results of niche breadths of the main populations were almost the same and the highest value of niche breadth in arbor layer, shrub layer and herb layer were Abies chensiensis, Sinarundinaria nitida and Carex lanceolata, respectively. Abies chensiensis was prone to form mixed forest with populations with high value of niche breadth. In the populations with high value of niche breadth, the niche similarity was generally higher accordingly. Niche overlaps extents of main populations in Abies chensiensis community were correspondingly lower, indicated that the environmental resource could be shared by every population and the community was comparative stable.

Based on the data collected from the plots investigation along with the implementation Levins, Shannon weiner index and niche overlap formulas in Mt. Qinling Shaanxi, the niche breadth values, niche similarity and niche overlap values of the main tree species were measured in the forestry of Abies chensiensis in this study. The results showed that: with the respective Levins and Shannon weiner index, the results of niche breadths of the main populations were almost the same and the highest value of niche breadth in arbor layer, shrub layer and herb layer were Abies chensiensis, Sinarundinaria nitida and Carex lanceolata, respectively. Abies chensiensis was prone to form mixed forest with populations with high value of niche breadth. In the populations with high value of niche breadth, the niche similarity was generally higher accordingly. Niche overlaps extents of main populations in Abies chensiensis community were correspondingly lower, indicated that the environmental resource could be shared by every population and the community was comparative stable.

According to the theory of forest growth cycle, forest communities are dynamic mosaic systems composed of patches in different developmental stages. On basis of the quandrats investigation carried out in a 1 hm² tropical montane rain forest in Bawangling, Hainan Province, the community characteristics of the whole forest stand were analyzed.The population and community features were studied based on the theory of forest cycle. The result showed that the utilization of ecological resources in the horizontal and vertical directions for trees of different life forms were relatively separate. Most shrubs and small statured trees had greater niche breadth values in the horizontal direction, and had less niche breadth values in the vertical direction ,and those for the middle or tall trees were on the contrary. The niche breadth for the rare and low density species were the least in both directions. With the progress of forest cycle, the frequency of different species presented in different patch types changed accordingly. The distribution patterns for most dominant trees and shrubs in the community were clumped, those for the trees having moderate individuals were uniform, and those for the low density species were random. In the process of forest cycle, the individuals owned by each species and the space occupied by each species decreased gradually. The numbers of species in different patch types in the forest cycle decreased with the increase of numbers of individuals. The numbers of species with 1 individuals and 2 individuals were most abundant ,and the numbers of species with more than 3 individuals decreased apparently in the investigated forest. Similarity analysis showed that the dynamic changes of patches in the forest cycle were somewhat continuous and gradual, the similarities between the neighboring stages were greater than those non_neighboring stages in the forest cycle. Calculation of niche breadth for different species on basis of the theory of forest cycle showed that the utilization of ecological resources in different patches by the low density species or those confined only in certain patches were comparatively less, while those species presented in most patches and had moderate numbers of individuals or moderate basal areas had greater utilizations for the ecological resources in the forest cycle.

According to the theory of forest growth cycle, forest communities are dynamic mosaic systems composed of patches in different developmental stages. On basis of the quandrats investigation carried out in a 1 hm² tropical montane rain forest in Bawangling, Hainan Province, the community characteristics of the whole forest stand were analyzed.The population and community features were studied based on the theory of forest cycle. The result showed that the utilization of ecological resources in the horizontal and vertical directions for trees of different life forms were relatively separate. Most shrubs and small statured trees had greater niche breadth values in the horizontal direction, and had less niche breadth values in the vertical direction ,and those for the middle or tall trees were on the contrary. The niche breadth for the rare and low density species were the least in both directions. With the progress of forest cycle, the frequency of different species presented in different patch types changed accordingly. The distribution patterns for most dominant trees and shrubs in the community were clumped, those for the trees having moderate individuals were uniform, and those for the low density species were random. In the process of forest cycle, the individuals owned by each species and the space occupied by each species decreased gradually. The numbers of species in different patch types in the forest cycle decreased with the increase of numbers of individuals. The numbers of species with 1 individuals and 2 individuals were most abundant ,and the numbers of species with more than 3 individuals decreased apparently in the investigated forest. Similarity analysis showed that the dynamic changes of patches in the forest cycle were somewhat continuous and gradual, the similarities between the neighboring stages were greater than those non_neighboring stages in the forest cycle. Calculation of niche breadth for different species on basis of the theory of forest cycle showed that the utilization of ecological resources in different patches by the low density species or those confined only in certain patches were comparatively less, while those species presented in most patches and had moderate numbers of individuals or moderate basal areas had greater utilizations for the ecological resources in the forest cycle.

Based on the data collected from 31 plots and using Levins, Hurlbert and Pianka formulas, this paper calculated and analyzed the niche breadths and overlaps of 24 tree and 29 shrub populations in Quercus aliena var. acuteserrata stands in Mt. Qinling, Shaanxi. The results showed that the Levins and Hurlbert's niche breadths of Quercus aliena var. acuteserrata , Pinus armandi, Toxicodendron vernicifluum, Populus davidiana and Pinus tabulaeformis in arbor layer were 3.695, 1.695, 1.325, 0.840, 0.702 and 0.036, 0.299, 0.568, 1.721, 2.701 respectively, and those of Corrylus heterophylla, Lespedeza formosa and Smilax vaginata in shrub layer were 1.833, 1.466, 0.984 and 0.111, 0.300, 0.594, respectively. In general, the niche overlaps between the species with bigger niche breadth and other species were higher, and those of the species having similar environmental requirements were also higher.

Based on the data collected from 31 plots and using Levins, Hurlbert and Pianka formulas, this paper calculated and analyzed the niche breadths and overlaps of 24 tree and 29 shrub populations in Quercus aliena var. acuteserrata stands in Mt. Qinling, Shaanxi. The results showed that the Levins and Hurlbert's niche breadths of Quercus aliena var. acuteserrata , Pinus armandi, Toxicodendron vernicifluum, Populus davidiana and Pinus tabulaeformis in arbor layer were 3.695, 1.695, 1.325, 0.840, 0.702 and 0.036, 0.299, 0.568, 1.721, 2.701 respectively, and those of Corrylus heterophylla, Lespedeza formosa and Smilax vaginata in shrub layer were 1.833, 1.466, 0.984 and 0.111, 0.300, 0.594, respectively. In general, the niche overlaps between the species with bigger niche breadth and other species were higher, and those of the species having similar environmental requirements were also higher.