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1.
Abies georgei var. smithii is an important plant species in Southeast Tibet, China. It has high ecological value in terms of biodiversity protection, as well as soil and water conservation. We analyzed the spatial pattern and associations of A. georgei var. smithii populations at different growth stages by using Ripley’s L function for point pattern analysis. The diameter structure was a nearly reverse ‘J’ shape. The amount of saplings and medium-sized trees accounts for a large part of the entire population, suggesting a high regeneration rate and an expanding population. In the transition from saplings to medium trees or to large trees, saplings show a significant aggregation distribution at small scales, while medium trees and large trees show a random distribution. There are significant inverse associations between saplings and medium trees and large trees at small scales, while there are no obvious associations between medium trees and large trees. The natural regeneration was affected by interspecific competition, and it was also affected by intraspecific competition. The joint effects of biological characteristics and environmental factors contribute to the spatial distribution pattern and associations of this A. georgei var. smithii population.  相似文献   

2.
We studied distribution and site conditions of epiphytic orchids in a gradient of human interference in Kathmandu valley, central Nepal. The aim was to understand the recent distribution pattern of epiphytic orchids, with respect to (i) the micro-site conditions and (ii) the type and intensity of land use. The occurrence of epiphytic orchids was recorded for a grid with 1.5 km cell size. The cells represent different types and intensities of human impact. Site factors such as bark rugosity, bark pH, diameter at breast height (dbh; 1.3 m) of host trees, exposure to wind and sunlight intensity were recorded. With regard to the species richness and abundance of epiphytic orchids, we compared different human impact categories from very strong human impact (settlement area) to very low human impact (national park). Remote sensing was used for a supervised classification of land cover. Ficus religiosa turned out to be the most important host species for orchids in urban areas, while Schima wallichii and Alnus nepalensis significantly host orchids in the other categories. Both species richness and abundance of epiphytic orchids were significantly higher under very low human impact (forest in national park) and also some remaining patches of primary forest than the other regions. Micro-climate is crucial for orchid populations. Host bark pH, bark rugosity, sunlight intensity and host exposure were significantly different for all human impact categories in order to harbour epiphytic orchid species. Habitats with a mixture of mature trees are suitable and essential for the conservation of viable populations of epiphytic orchids in settled areas. The study reveals that to improve the population size of orchids it is essential for future urban forestry to: (i) Protect old trees as carriers of existing epiphytic orchid diversity, (ii) protect medium old trees to ensure that they may become old trees, (iii) plant new host trees for the future, (iv) plant in groups instead of single isolate trees. Trees should especially be planted in areas where orchids still exist to provide more trees for orchid population enlargement (e.g. along riparian system). Native species should be favoured; the pool of such native host species is wide.  相似文献   

3.
Epiphytic plant species are an important part of biological diversity. It is therefore essential to understand the distribution pattern and the factors influencing such patterns. The present study is aimed at observing the patterns of species richness, abundances and species composition of epiphytic orchids and ferns in two subtropical forests in Nepal. We also studied the relationship of host plants (Schima wallichii and Quercus lanata) and epiphyte species. Data were collected in Naudhara community forest (CF) and the national forest (NF) in Shivapuri Nagarjun National Park. The data were analyzed using univariate and multivariate tests. In total, we recorded 41 species of epiphytes (33 orchid and 8 fern species). Orchid species abundance is significantly higher in CF compared to NF. Orchid species richness and abundance increased with increasing southern aspect whereas it decreased with increasing canopy cover, and fern species richness increased with host bark roughness. Orchid abundance was positively correlated with increasing bark pH, stem size, tree age and tree height and negatively correlated with increasing steepness of the area. Likewise, fern abundances were high in places with high canopy cover, trees that were tall and big, but decreased with increasing altitude and southern aspect. The composition of the orchid and fern species was affected by altitude, aspect, canopy cover, DBH, number of forks and forest management types. We showed that the diversity of orchid and fern epiphytes is influenced by host characteristics as well as host types. The most important pre-requisite for a high epiphyte biodiversity is the presence of old respectively tall trees, independent of the recent protection status. This means: (i) for protection, e.g. in the frame of the national park declaration, such areas should be used which host such old tall trees; and (ii) also in managed forests and even in intensively used landscapes epiphytes can be protected by letting a certain number of trees be and by giving them space to grow old and tall.  相似文献   

4.
Topographic and edaphic variables are the main ecological factor determining species spatial variability on mountainous forests. A field study was performed in central Alborz to investigate how the edaphic and topographic parameters can affect the tree and shrub communities. Initially, 27 forest stands were identified and the homogeneous units were separated regarding physiognomy. In each single homogeneous unit, one random sample plot (1000 m2) and totally 43 plots were established. In each plot, the presence and abundance of all trees and shrubs were recorded and four soil samples were taken from depths of 0-5 and 5-20 cm. Concerning classification results, eight different forest communities were identified. The lowest and highest soil pH values were observed in Malus orientalis and pistacia-Amygdalus communities, respectively. The water saturation percent of pure- and mixed Juniperus excelsa and Rhus coriaria was the highest amongst communities. The clay content was the highest in pure J. excelsa. The 0-5 organic matter and Nitrogen content in mixed J. excelsa were significantly higher than pure J. excelsa and other communities. The CCA (Canonical Correspondence Analysis) results indicated that the altitude, precipitation, pH, EC, SP, clay and CaCO3 are the most important factors determine the distribution of trees and shrub in central Alborz  相似文献   

5.
Natural habitat of Hippophae salicifolia in Central Himalaya is continuously being degraded due to habitat destruction and harvesting.Although logging is prohibited,habitat destruction has increased because of regular road construction,repairing and broadening activities.In addition,Hippophae resources are continuously being harvested by lopping(both partial and complete) for fuelwood,fodder and fruits in higher Himalayan region.This paper presents a detailed analysis of relationship between density,demographic structure,and harvesting of H.salicifolia growing pockets in the five major valleys(Gangotri,Yamunotri,Niti,Mana and Bhyundhar) of Uttarakhand in Central Himalaya,India.A total of 120 quadrats were laid randomly to study population structure,regeneration,sex ratio and lopping using quadrats of 100 m 2(24 in each valley) in Hippophae growing patches.Our study shows that the density,size distribution,and regeneration of Hippophae vary considerably among the major valleys.Trees in the Yamunotri valley have the highest density of large trees but the lowest density of seedlings.In contrast,there are few large trees but many seedlings in the Mana valley.The number and size of lopped trees also varied among the valleys.Lopping was greatest in Bhyundhar(11.4%) and Yamunotri(19.7%) and least in Niti(3.9%).The size of lopped trees differed substantially as well.In Bhyundhar,the largest trees were taken while saplings were taken in Yamunotri.Our study revealed that unsustainable harvesting from plants for fuel,fencing and fruits along with road broadening activities in Central Himalaya are the main cause of habitat destruction.Our research highlights the urgent need for in-situ and ex-situ conservation of Hippophae salicifolia so that it’s potential can be harnessed sustainably by rural hill societies for their socio-economic development.  相似文献   

6.
Biodiversity patterns of free-living marine nematodes were studied using specific,taxonomic and phylogenetic diversity measures in the southern Yellow Sea,China.The results showed that the average of Shannon-Wiener diversity index(H′) in the study area was 3.17.The higher values were distributed in the east part of Shandong coastal waters and north part of Jiangsu coastal waters,while the lower values were distributed in the southern Yellow Sea Cold Water Mass(YSCWM).The average of taxonomic diversity(Δ) was 62.09 in the study region.The higher values were distributed in the transitional areas between the coastal areas and the southern YSCWM,while the lower values were distributed near the north part of Jiangsu coastal waters and the YSCWM.Results of correlation analysis of species diversity and taxonomic diversity showed that some of the two kinds of diversity index were independent,which suggested that combining the two kinds of diversity indices can reflect the ecological characteristics better.A test for 95% probability funnels of average taxonomic distinctness and variation in taxonomic distinctness suggested that Station 8794(in the YSCWM) was outside of the 95% probability funnels,which may be due to the environmental stress.Results of correlation analysis between marine nematodes biodiversity and environmental variables showed that the sediment characteristics(Md? and Silt-clay fraction) and phaeophorbide a(Pha-a) were the most important factors to determine the biodiversity patterns of marine nematodes.  相似文献   

7.
Woody debris (WD) is an important part of natural Pinus tabulaeformis mixed stands, and it affects the forest ecosystem stability and development. The WD spatial patterns are especially important structural characteristics that can provide insights into forest dynamics. In this paper, the WD storage, WD spatial patterns and WD associations among the main species were examined in the natural secondary forest on Loess Plateau in northwest China. Data were collected in a 1 ha (100 m × 100 m) permanent plot, and all the trees with a diameter at breast height of more than 3 cm were measured and stem-mapped. Ripley’s K functions from the spatial-point-pattern-analysis method were used to analyze the spatial distribution and associations. The results showed that: (1) The total storage of WD was 10.73 t/ha, fallen wood was the main source of WD, and the majority diameters were greater than 20 cm, and in intermediate levels of decay; (2) The overall spatial pattern was closely related to the spatial scale, which exhibited an aggregated pattern on a small scale, and a random pattern on a large scale. The spatial patterns of coarse woody debris also gradually transitioned from an aggregated pattern in fine scales to a random pattern in broader spatial scales, which matched the overall spatial pattern. The spatial intensity was gradually decreased with the increasing diameters, and increased with the decomposition classes; (3) The WD of Pinus tabulaeformis species was negatively associated with Betula platyphylla and Populus davidiana on a small scale but positively associated with these species on a large scale. The spatial pattern and interspecies relations were the results of long-term interactions between the natural secondary forest community and the surrounding natural environment. These findings would provide a scientific basis for the sustainable management and protection of natural secondary forest ecosystems on Loess Plateau.  相似文献   

8.
Mountainous rangelands play a pivotal role in providing forage resources for livestock, particularly in summer, and maintaining ecological balance. This study aimed to identify environmental variables affecting range plant species distribution, ecological analysis of the relationship between these variables and the distribution of plants, and to model and map the plant habitats suitability by the Random Forest Method(RFM) in rangelands of the Taftan Mountain, Sistan and Baluchestan Province, southeastern Iran. In order to determine the environmental variables and estimate the potential distribution of plant species, the presence points of plants were recorded by using systematic random sampling method(90 points of presence) and soils were sampled in 5 habitats by random method in 0–30 and 30–60 cm depths. The layers of environmental variables were prepared using the Kriging interpolation method and Geographic Information System facilities. The distribution of the plant habitats was finally modelled and mapped by the RFM. Continuous maps of the habitat suitability were converted to binary maps using Youden Index(?) in order to evaluate the accuracy of the RFM in estimation of the distribution of species potentialhabitat. Based on the values of the area under curve(AUC) statistics, accuracy of predictive models of all habitats was in good level. Investigating the agreement between the predicted map, generated by each model, and actual maps, generated from fieldmeasured data, of the plant habitats, was at a high level for all habitats, except for Amygdalus scoparia habitat. This study concluded that the RFM is a robust model to analyze the relationships between the distribution of plant species and environmental variables as well as to prepare potential distribution maps of plant habitats that are of higher priority for conservation on the local scale in arid mountainous rangelands.  相似文献   

9.
The spatial distribution of siliceous microfossils (diatoms and silicoflagellates) in the surface sediments was mapped at 113 sites in the Yellow Sea and sea areas adjacent to the Changjiang (Yangtze) River, China. In total, 267 diatom taxa and two silicoflagellate species were identified from the sediments. The spatial variations in abundance and diversity were classified into three distinct geographic patterns using Q mode clustering: a south-north geographic pattern, a coastal-offshore pattern and a unique pattern in the Changjiang River mouth. The south-north geographic pattern was related to the spatial variations in sea temperature. Coscinodiscus oculatus, a warm-water species, indicated these variations by a gradual decrease in abundance from the south to the north. The coastal-offshore pattern was in response to the spatial variations in salinity. Cyclotella stylorum, Actinocyclus ehrenbergii and Dictyocha messanensis, the dominant brackish species in coastal waters, significantly decreased at the isobaths of approximately 30 m, where the salinity was higher than 31. Paralia sulcata and Podosira stelliger indicated the impact of the Yellow Sea Warm Current in the central Yellow Sea. The unique pattern in the Changjiang River mouth showed the highest species diversity but lower abundance, apparently because: freshwater input can significantly increase the proportion of brackish species; nutrients can supply the growth of phytoplankton; and high sedimentation rates can dilute the microfossil abundance in the sediments. Our results show that an integration of environmental factors (e.g., nutrient levels, sedimentation rate, sea temperature, salinity and water depth) determined the spatial characteristics of the siliceous microfossils in the surface sediments.  相似文献   

10.
The survival chance of epiphytic orchids today not only depends on the natural site conditions required by the orchids but also on anthropogenic changes in site conditions.This study answers two questions:(1) What is the ecological niche of the different epiphytic orchid species?(2) What are the ecological factors that threaten epiphytic orchid's population under anthropogenic disturbances? Our study area was the Kathmandu valley,Nepal,with its subtropical forest.We established 156 systematically selected sampling points in the Kathmandu area covering different types of ecosystems under human impacts such as densely populated area,agricultural land,mixed agricultural and settled area,old tree patches,and a natural forest in a national park.The ecological niche of the orchid species was analyzed with a principal component analysis(PCA).The correlations between the different site factors were statistically significant.Spearman's rank correlation matrices showed that the variables land-use intensities with altitude,and height with diameter in breast height(dbh) of host had the highest significant positive correlation coefficient(0.67 and 0.64 respectively).On the other hand,host bark p H and altitude as well as land use had a significantly strong negative correlation coefficient(-0.80 and-0.61,respectively).Different epiphytic orchid species interact differently with the given set ofenvironmental factors:for occurrence of Vanda cristata there is no single environmental factor of special influence,while for Rhynchostylis retusa high bark p H and high light availability are important.First two axis of the PCA explained more than 50% of the total variance.Most orchid species occupy a specific,narrow niche in this ecological space.The main causes of anthropogenic influence of orchid population in the Kathmandu Valley are loss of adequate host trees(species and size) and increasing air pollution,resulting in increasing host bark p H.  相似文献   

11.
This paper highlights the quantitative estimates of plant species diversity and ecosystems of the Rohtang Pass,which is one of the most preferred visiting spots by tourists in Himachal Pradesh （H.P.）,India. In spite of high pressure of anthropogenic activities,the Rohtang Pass still harbours a variety of flowering plants with economic value,including various medicinal herbs. In order to observe species diversity in different landscape elements （LSEs）,ground surveys were conducted in nine unique LSEs within the elevation range between 3624 m and 4332 m. Plant community structure in each LSE was studied using stratified random sampling where a total 56 quadrats of 1 m^2 in size for herbs and 7 quadrats of 25 m^2 for shrubs were made. Of the total 50 plant species belonging to 15 families recorded in different random quadrats,24 species were found of medicinal value. Maximum species richness （18） and value of Shannon diversity （H＇=2.2648） were observed on northeast-facing slope in Picrorhiza kurrooa dominated LSE in moist area,followed by Rheum emodi LSE （species richness = 17 and H＇ = 2.4141） distributed on south-facing slope. Maximum values of species richness and Shannon diversity in Rheum emodi LSE were observed between 8 ～ 12 and 1.4797 ～ 2.1911,respectively. Rhododendron anthopogon dominated LSE on northwest-facing slope was found least diverse in terms of species richness where the Simpson index of dominance （D） was 0.4205. The species were equal in abundance in P. kurrooa LSE on east-facing slope and Pleurospermum candollii LSE on north-facing slope,showing the maximum similarity in terms of species distribution between the two LSEs. Low turnover of species across common LSEs gives an idea regarding their limited distribution. Five species of threatened category according to the IUCN criteria were observed in seven LSEs. The largest population of threatened medicinal plants was recorded on northeast and northwest-facing slopes where population density of Bergenia stracheyi （  相似文献   

12.
Sipunculus nudus is an important economic species because of its high nutritional and medicinal values. The exploitation and utilization of S. nudus primarily occur in the coastal regions of the Beibu Gulf. However, wild resource of S. nudus is rapidly decreasing because of the overexploitation, which has led to considerable developments of artificial breeding techniques. The cultivation scale of S. nudus has increased in response to successful artificial breeding; however, methods for culturing S. nudus in tidal flats or ponds require further study. Most studies have focused on the breeding, nutrition, medical value and ecological impact of these worms. Studies on the distribution, sediment requirements, nutrition characteristics, breeding techniques and aquaculture ecology of this species are summarized in this paper to promote the development of the aquaculture industry for S. nudus. The high biomass of S. nudus in the Beibu Gulf is positively correlated with the sediment characteristics and water quality of the region. The production of peanut worm has improved to some extent through culturing; however, the nutrient value and ecological environment problems have been observed, which reflect the over exploitation of trace elements and the sediment. These problems will worsen unless they are resolved, and the release of organic materials, nitrogen and phosphorus during harvesting impacts the coastal environment. Moreover, genetic erosion is a potential risk for larvae in artificial breeding programs in tidal flats. Therefore, culturing and collecting methods should be improved and the wild resource conservation should be implemented to promote the sustainable development of the peanut worm.  相似文献   

13.
Impact of anthropogenic disturbance on species diversity and vegetation structure of a lowland tropical rainforest was studied in the foothills of Eastern Himalaya, India. Tree species richness, density, basal area and the diversity indices were found significantly (P<0.05) decreased with the increasing level of disturbances whereas, shrub density, basal area and herb density significantly increased with increasing disturbance level. In case of shrubs, Simpson’s dominance index significantly (P<0.007) increased along the disturbance gradient, whereas Pielou’s evenness index significantly (P<0.005) decreased with an increasing level of disturbance. Shannon-Weiner diversity index for herbs significantly (P<0.016) increased with increasing disturbance whereas, Simpson’s dominance index was significantly (P<0.013) declined along the disturbance gradient. Results revealed that 10–50 cm dbh classes constituted the highest stem density, and highest basal area was recorded in the >100 cm dbh class in all three sites. Density of the matured trees decreased with increasing DBH whereas, tree basal area tended to increase with increasing DBH in all three sites. Tree species richness was highest in the lower DBH classes. 62.07% of the total tree species regenerated in the largely undisturbed site followed by 50% in the mildly disturbed and 26.32% in the highly disturbed site. The overall regeneration condition was found to be good in the largely undisturbed site. Mildly disturbed site exhibited fair regeneration and so was in the highly disturbed site. Discernable variations in species composition, diversity, regeneration and tree population structure revealed the impact of anthropogenic disturbances on rainforest vegetation dynamics. Higher degree of disturbance was furtherly found not only affecting species diversity but also promoting the growth of invasive weed species. Dominance of Hydnocarpus kurzii and Crypteronia paniculata in the highly disturbed site also indicated that these less-valued timber species may benefit from the vegetation mosaic produced by the disturbance; so differences in abundance of these species may be useful for bio-indication. Furthermore, present study suggests the need of adequate biodiversity conservation measures and adaptation of sustainable forest management approaches in disturbed areas of lowland tropical rainforest in the foothills of eastern Himalaya, India.  相似文献   

14.
Oplegnathus fasciatus (rock bream) is a commercial rocky reef fish species in East Asia that has been considered for aquaculture. We estimated the population genetic diversity and population structure of the species along the coastal waters of China using fluorescent-amplified fragment length polymorphisms technology. Using 53 individuals from three populations and four pairs of selective primers, we amplified 1 264 bands, 98.73% of which were polymorphic. The Zhoushan population showed the highest Nei’s genetic diversity and Shannon genetic diversity. The results of analysis of molecular variance (AMOVA) showed that 59.55% of genetic variation existed among populations and 40.45% occurred within populations, which indicated that a significant population genetic structure existed in the species. The pairwise fixation index F st ranged from 0.20 to 0.63 and were significant after sequential Bonferroni correction. The topology of an unweighted pair group method with arithmetic mean tree showed two significant genealogical branches corresponding to the sampling locations of North and South China. The AMOVA and STRUCTURE analyses suggested that the O. fasciatus populations examined should comprise two stocks.  相似文献   

15.
Snow depth is a general input variable in many models of agriculture,hydrology,climate and ecology.This study makes use of observational data of snow depth and explanatory variables to compare the accuracy and effect of geographically weighted regression kriging(GWRK)and regression kriging(RK)in a spatial interpolation of regional snow depth.The auxiliary variables are analyzed using correlation coefficients and the variance inflation factor(VIF).Three variables,Height,topographic ruggedness index(TRI),and land surface temperature(LST),are used as explanatory variables to establish a regression model for snow depth.The estimated spatial distribution of snow depth in the Bayanbulak Basin of the Tianshan Mountains in China with a spatial resolution of 1 km is obtained.The results indicate that 1)the result of GWRK's accuracy is slightly higher than that of RK(R~2=0.55 vs.R~2=0.50,RMSE(root mean square error)=0.102 m vs.RMSE=0.077 m);2)for the subareas,GWRK and RK exhibit similar estimation results of snow depth.Areas in the Bayanbulak Basin with a snow depth greater than 0.15m are mainly distributed in an elevation range of 2632.00–3269.00 m and the snow in this area comprises 45.00–46.00% of the total amount of snow in this basin.However,the GWRK resulted in more detailed information on snow depth distribution than the RK.The final conclusion is that GWRK is better suited for estimating regional snow depth distribution.  相似文献   

16.
Dominant species of zooplankton community vary with latitude. Though China possesses a vast coastal area in northwestern Pacific, studies on the latitudinal dominant species gradient are rare. We collected zooplankton samples from Haizhou Bay(34.56?–35.19?N, 119.51?–120.30?E), Yueqing Bay(28.14?–28.38?N, 121.10?–121.21?E) and Dongshan Bay(23.65?–23.90?N, 117.45?–117.60?E) in May 2012 and May 2013 to preliminarily characterize the latitudinal dominant species distribution. All the samples were collected vertically using a 0.505 mm mesh plankton net with 0.8 m in mouth diameter from bottom to surface. Calanus sinicus, Aidanosagitta crassa, Labidocera euchaeta, Zonosagitta nagae, Acartia pacifica and Paracalanus parvus were found to be dominant. C. sinicus was the most dominant species and the unique one occurred in all three bays. With latitude decreasing, both the abundance and proportion of C. sinicus declined sharply. Cluster analysis showed that the 6 dominant species could be divided into 3 groups, based on their occurrences in the three bays. Our results suggested that the distribution of dominant species along the coast of China has a significant latitudinal gradient. C. sinicus which widely distributes in the coastal water of the northwestern Pacific can well adapt to the temperature at different latitudes. The high abundance in Haizhou Bay indicated that C. sinicus was an exemplary warm-temperate species, and more commonly occurs in the north of China seas. The ecological characteristics of dominant species change from warm-temperate type in high-latitudinal bays to warm water type in low-latitudinal bays.  相似文献   

17.
Analyzing and understanding the structure and growth dynamics of forests at different stages is helpful to promote forest succession, restoration and management. Three spots representing three succession stages of spruce-fir mixed forest(SF: polar-birch secondary forest, MF: spruce-fir mixed forest and PF: spruce-fir near primary forest) were established. Structure, growth dynamics during two growth seasons for dominant tree species, regeneration were examined, and a univariate O-ring function statistic was used to analyze the spatial patterns of main regeneration tree species. Results showed that,(1) composition of tree species, periodic annual increment(PAI) of the diameter at breast height(DBH), basal area for overstory trees and of ground diameter(DGH) for saplings, were significantly different with the succession;(2) the current species composition and regeneration dynamics of SF suggested a development towards spruce-fir mixed forests. Pioneer species like Betula platyphyllaa will gradually disappear while climax species, such as Abies nephrolepis, Pinus koraiensis, Picea koraiensis and Tilia amurensis will dominate forest stands;(3) Despite the highest volume occurring in PF, and saplings in it grew better than in the others, this forest type is unstable because of its unsustainable structure of DBH class and insufficient regeneration; and(4) MF had the most reasonable distribution of DBH class for adult trees(DBH 5.0 cm) and DGH class for saplings(H ≥30 cm and DBH ≤5 cm), as well as an optimal volume increment. Limiting canopy opening size can lessen the physiological stress and promote the growth and competitive status of regeneration. Management implications for increasing the gaps and thus creating better growth conditions for understory saplings and facilitating forest succession were discussed.  相似文献   

18.
Dinoflagellates in the genus Symbiodinium, including nine clades (A–I), mainly form mutualistic symbioses with corals. More than 100 Symbiodinium molecular types have been identified by the ITS2-based genotype method within any given clade, and specifically within Symbiodinium clade C. However, the genotype identification method using the ITS2 sequence is likely to lead to high diversity estimates due to the intra-genomic variations in the ITS2 space; thus, further validation is essential for a correct identification. In this study, the molecular diversity of Symbiodinium ITS2 sequences cloned from two stone corals, Acropora sp. SY-01 and Pocillopora sp. SY-05, and one soft coral, Sarcophyton sp. SY-07, living in the northern part of South China Sea (SCS), were analyzed and compared using the ITS2-based genotype identification method, coupled with ITS2-based secondary structural and phylogenetic analyses. As the result, 12 Symbiodinium ITS2 genotypes were identified, while only six and three Symbiodinium ITS2 genotypes were supported by ITS2-based secondary structural and phylogenetic analyses, respectively. In addition, no shared Symbiodinium ITS2 genotypes were observed among the three coral species, suggesting coral species-dependent Symbiodinium genotypes were within clade C. In summary, the present study provides a theoretical basis for validating the molecular diversity of Symbiodinium ITS2 genotypes in corals.  相似文献   

19.
Wenchuan earthquake on 12 May 2008 triggered numerous landslides, which disturbed vast areas of vegetation in northwest Sichuan. However, based on our primary field investigation at Xiejiadian landslide in July 2009, we found an obvious increase of the number of plant species and then we made a hypothesis that, after earthquake, vegetation at this landslide might recover by itself. In this paper, we conduct a newly field investigation at Xiejiadian landslide during November 2014 to verify this hypothesis. We investigated plant species composition at total 56 sites (trees 4, shrubs 16 and herbs 36, respectively), and calculated the Schluter’s variance ratio, important values, x2 test, association coefficient, Ochiai index, Pearson’s and Spearman’s correlation coefficients, and Ecological species groups. Species sharply increased to 84 species belonging to 66 genera and 54 families, forming a complete life form containing trees, shrubs, herbs, and ground layers while only herbs detected in 2009. Moreover, an overall positive and moderately related interspecies association was detected for most of species pairs. Of total 84 species, twenty five were identified as dominant species and could be divided into four positive ecological species groups. This study verified our proposed hypothesis of self-recovery of vegetation in landslide triggered by the earthquake, and found Alnus cremastogyne, Rhus chinensis, Litsea cubeba, Vitis piasezkii and Anemone vitifolia would play a constructive role during the continuing succession of vegetation at Xiejiadian landslide.  相似文献   

20.
The neon flying squid (Ommastrephes bartramii) is a short-lived opportunistic species widely distributed in subtropical and temperate waters in the North Pacific Ocean. The life cycle of O. bartramii from planktonic eggs to nektonic adults is closely linked to oceanographic conditions. The fluctuations in O. bartramii abundance and distribution tend to increase and widen continuously due to the heavy influences of ocean-climate events on various spatio-temporal scales. In this study, we reviewed the interaction between O. bartramii and oceanography variability in the North Pacific with respect to large-scale climatic-oceanic phenomena including El Niño, La Niña, Kuroshio, Oyashio and Pacific Decadal Oscillation (PDO), as well as regional environmental variables such as sea surface temperature (SST), sea surface height (SSH), sea surface salinity (SSS), chlorophyll-a (Chl-a) concentration, and plankton density. The population dynamics of O. bartramii is mediated mainly by meso- and large-scale climatic-oceanic events (e.g., Kuroshio and Oyashio Currents) rather than other local environmental conditions (e.g., SST and Chl-a concentration), because all of the oceanographic influences are imposed on the context of large-scale climate changes (e.g., PDO). An unstructured-grid finite-volume coastal ocean model coupled with an individual-based model is proposed to simulate relevant physical-biological oceanographic processes for identifying ocean-climate influence and predicting O. bartramii distribution and abundance in the North Pacific. Future research needs to be focused on improving the knowledge about early life history of O. bartramii and evaluating the relationship between marine physical environment and two separate passive drifting life stages of O. bartramii including free-floating eggs and planktonic paralarvae.  相似文献   

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