The marine-continental transitional shale of the Upper Permian Longtan Formation is widely distributed in Hunan and shows significant exploration potential.Frequent changes in lithofacies have however notably influenc...The marine-continental transitional shale of the Upper Permian Longtan Formation is widely distributed in Hunan and shows significant exploration potential.Frequent changes in lithofacies have however notably influenced the shale gas enrichment.The strata of the Longtan Formation in the Shaoyang Depression,central Hunan,were taken as the study object for this project.Three lithofacies assemblages were identified:shale interbedded with sandstone layer(SAL),sandstone interbedded with shale layer(ASL)and laminated shale layer(LSL).The SAL shale shows significant variability in hydrocarbon generation potential,which leads to shale gas characterized by'hydrocarbon generation in high total organic carbon(TOC)shale,retention in low TOC shale and accumulation in sandstone'.The ASL shale,influenced by the redox conditions of the depositional environment,shows a lower concentration of organic matter.This results in an enrichment model of'hydrocarbon generation and accumulation in shale,with sealing by sandstone'.The laminar structure of LSL shale causes both quartz and clay minerals to control the reservoir.Shale gas is characterized by'hydrocarbon generation in mud laminae,retention and accumulation in silty laminae,with multiple intra-source migration paths'.In the marine-continental transitional shale gas system,the enrichment intervals of different types of shale gas reservoirs exhibit significant variability.展开更多
To reveal the deterioration mechanism of coal-rock assemblages under chemical corrosion and dynamic loading,chemical corrosion and dynamic impact experiments were conducted.Under different chemical corrosion condition...To reveal the deterioration mechanism of coal-rock assemblages under chemical corrosion and dynamic loading,chemical corrosion and dynamic impact experiments were conducted.Under different chemical corrosion conditions,the weakening characteristics,observable characteristics,softening characteristics of the dynamic parameters,dynamic failure characteristics,dynamic failure forms and dynamic microscopic characteristics were analyzed.Under each corrosion condition,the dynamic elastic modulus,dynamic deformation modulus and dynamic peak intensity tended to decrease with immersing time.The dynamic elastic modulus,dynamic deformation modulus and dynamic peak intensity exhibited an inverted U-shaped trend.Under dynamic impact,the failure process of acidly corroded samples can be divided into the following stages:the initial stage,elastic energy accumulation stage,local failure of coal and secondary rock crack expansion stage,coal fragment ejection stage,rock spalling stage and complete instability stage.Under dynamic impact,failure modes exist:coal crushing failure,rock fragmenting failure,rock splitting failure and full splitting failure.After impact failure,sample fragments are distributed in powder,granular,cone and block forms.Based on Zhu-Wang-Tang nonlinear viscoelastic properties,a model considering chemical corrosion and impact damage was proposed.The combined effects of chemical and impact-induced damage on the dynamic mechanical properties of coal-rock assemblages were systematically analyzed.展开更多
The Ediacaran–Ordovician strata within three major marine basins(Tarim,Sichuan,and Ordos)in China are analyzed.Based on previous studies focusing on the characteristics of the Neoproterozoic–Cambrian strata within t...The Ediacaran–Ordovician strata within three major marine basins(Tarim,Sichuan,and Ordos)in China are analyzed.Based on previous studies focusing on the characteristics of the Neoproterozoic–Cambrian strata within the three major basins(East Siberian,Oman,and Officer in Australia)overseas,the carbonate–evaporite assemblages in the target interval are divided into three types:intercalated carbonate and gypsum salt,interbedded carbonate and gypsum salt,and coexisted carbonate,gypsum salt and clastic rock.Moreover,the concept and definition of the carbonate-evaporite assemblage are clarified.The results indicate that the oil and gas in the carbonate-evaporite assemblage are originated from two types of source rocks:shale and argillaceous carbonate,and confirmed the capability of gypsum salt in the saline environment to drive the source rock hydrocarbon generation.The dolomite reservoirs are classified in two types:gypseous dolomite flat,and grain shoalµbial mound.This study clarifies that the penecontemporaneous or epigenic leaching of atmospheric fresh water mainly controlled the large-scale development of reservoirs.Afterwards,burial dissolution transformed and reworked the reservoirs.The hydrocarbon accumulation in carbonate-evaporite assemblage can be categorized into eight sub-models under three models(sub-evaporite hydrocarbon accumulation,supra-evaporite hydrocarbon accumulation,and inter-evaporite hydrocarbon accumulation).As a result,the Cambrian strata in the Tazhong Uplift North Slope,Maigaiti Slope and Mazatag Front Uplift Zone of the Tarim Basin,the Cambrian strata in the eastern-southern area of the Sichuan Basin,and the inter-evaporite Ma-4 Member of Ordovician in the Ordos Basin,China,are defined as favorable targets for future exploration.展开更多
To better understand the community patterns mediated by connectivity in artificial reefs of coastal areas, it is necessary to understand the distribution and coexistence of organisms with artificial reefs area and adj...To better understand the community patterns mediated by connectivity in artificial reefs of coastal areas, it is necessary to understand the distribution and coexistence of organisms with artificial reefs area and adjacent waters. This study was conducted to examine main catches assemblages collected by trawls in Haizhou Bay,which included five habitats: the artificial reef area(AR), aquaculture area(AA), natural area(NA), estuary area(EA) and comprehensive effect area(CEA). The result shows that the total abundances of species in the five habitats were highly different(univariate PERMANOVA: P = 0.001, n = 24), but some species were also unique in their habitat(e.g. Scapharca subcrenata and Glossaulax didyma in AA). The body size distribution of specific species between habitats are different. For Collichthys lucidus, their body size in AR(14.63 cm ± 1.64 cm) and EA(14.3 cm ± 0.85 cm) is higher than that in NA(10.65 cm ± 1.64 cm), CEA(11.28 cm ± 1.85 cm) and AA(12.1 cm ±0.43 cm), which indicates the potential connection from AR to EA mediated by their adult population. We concluded that artificial reefs in AR can be considered key components that have the ability to support species assemblages in adjacent habitats. This study has implications for the conservation and monitoring of species assemblages in coastal areas in terms of that artificial reefs can be applied in different stages of habitat protection implementation and in different combinations of scenarios.展开更多
Coal and oil shale are two common sedimentary energy sources which are often symbiotically developed in M esozoic- Cenozoic continental fault basins. However, the mechanisms and characteristics of the symbiotic develo...Coal and oil shale are two common sedimentary energy sources which are often symbiotically developed in M esozoic- Cenozoic continental fault basins. However, the mechanisms and characteristics of the symbiotic development are not yet clearly known. In this research study, the typical continental fault basins of eastern China were chosen as examples for the purpose of conducting an examination of the coal and oil shale symbiotic assemblage types, genetic environmental differences, and transformation mechanisms, as well as the development and occurrence characteristics o f different assemblage types. Through a large number of investigations, systematic experimental testing, and sequence stratigraphy studies, the following conclusions were obtained:(1) There were five types of coal and oil shale symbiotic assemblages observed in the continental fault basins,(2) The development of coal and oil shale deposits requires a warm and humid climate, stable structure, abundant organic matter supply, a certain water depth, and a lower terrestrial source debris supply. The observed differences were that the water depth conditions were diversified in the study area, as well as the sources, types, and content of the organic matter.(3) The rapid transformations of the coal and oil shale genetic environments were mainly controlled by the tectonic settings and climatic conditions, which were determined to control the changes in the water depths, salinity,redox conditions, and lake productivity of the genetic environments. Also, in the symbiotic assemblages, genetic environment changes had induced the development of oil shale deposits, which gradually evolved into coal genetic environments.(4) In the isochronous sequence stratigraphic framework of the coal and oil shale symbiotic assemblages, the lake expansion system tracts (EST) were determined to be the most beneficial to the growth o f all the types of assemblages and were characterized by more assemblage development phases and smaller bed thicknesses. From the early to the late stages of the EST, and from the lakesides to lake centers, the thicknesses of the coal seams in the symbiotic assemblages showed trends of thinning, while the thicknesses of the oil shale deposits exhibited increasing trends. The early stages of high stand system tracts were found to be beneficial to the development of the symbiotic assemblages of coal seams overlying the oil shale. This tract type generally presented large bed thicknesses and distribution ranges. The low stand system tract and the late high stand system tract were determined to be unconducive to the development of the symbiotic assemblages.展开更多
Shrub presence has an important effect on the structuring of ground beetles in desert ecosystems. In this study, in order to determine how shrubs and different species influence ground beetle assemblages in a sandy de...Shrub presence has an important effect on the structuring of ground beetles in desert ecosystems. In this study, in order to determine how shrubs and different species influence ground beetle assemblages in a sandy desert scrubland dominated by two different shrub species, namely Calligonum mongolicum and Nitraria sphaerocarpa, we sampled the ground beetles using pitfall traps during spring, summer and autumn in 2012. At the community level, the activity density of the ground beetles was shown to be significantly higher under shrubs than in intershrub bare habitats in spring; but an opposite pattern occurred in autumn, suggesting the presence of sea- son-specific shrub effects on the activity density of the ground beetles. Meanwhile, at the trophic group level, the activity density and species richness of predators were significantly greater under shrubs than in intershrub bare habitats in spring, whereas an opposite trend occurred on the activity density in autumn. N. sphaerocarpa shrubs had a positive effect on the activity density of herbivores in the three seasons, and C. mongolicum shrubs had a positive effect on the activity density of detritivores in spring and autumn. At the species level, more Microdera sp. was captured under shrubs than in intershrub bare habitats in spring. During the same time, we also found that C. mongolicum shrubs had a positive effect on Blaps gobiensis in spring, Carabus sp. in autumn, and Tentyria sp. in spring and autumn, and N. sphaerocarpa shrubs had a positive effect on Cyphogenia chinensis, Sternoplax setosa in spring and summer, and Curculionidae sp. 1 in summer and autumn. The study results suggest that shrub presence, shrub species and season variation are important factors for ground beetle assemblages in this desert ecosystem, but the responses of beetles differed among trophic and taxonomic levels.展开更多
The pollen and spores found in the Early Cretaceous strata of two cores from the Shuangliao Fault Depression were studied systematically, and two palynological assemblages have been recognized. Assemblage I from the Y...The pollen and spores found in the Early Cretaceous strata of two cores from the Shuangliao Fault Depression were studied systematically, and two palynological assemblages have been recognized. Assemblage I from the Yingcheng Formation is named Paleoconiferus-Pinuspollenites; the assemblage is characterized by an extremely high content of Paleoconifer pollen. Assemblage II from Member 1 of the Denglouku Formation is named Cicatricosisporites-Cyathidites-Pinuspollenites; the assemblage is characterized by the abundant presence of Laevigati spores, but less Paleoconifer pollen. According to the palynological data and zircon U-Pb dating, the geological age of the Yingcheng Formation is thought to be Aptian-Albian, and that of the Denglouku Formation is thought to be Early Albian. On the basis of the composition of each assemblage, we can infer that during the depositional period of the Yingcheng Formation, the paleovegetation was mainly conifer forest, the paleoclimate was consistent with the temperate climate of today, and the paleoenvironment was humid feature. During the depositional period of Member 1 of the Denglouku Formation, the paleovegetation was mainly conifer forest and shrubs, the paleoclimate was consistent with the subtropical climate of today, and the paleoenvironment was humid. The results significantly improve our understanding of the stratigraphy in the Shuangliao Fault Depression, provide biostratigraphic evidence for the division and correlation of Early Cretaceous strata in the Shuangliao Fault Depression, and provide new data for analyzing paleovegetation and paleoclimate in the Songliao Basin.展开更多
53 pollen traps and surface samples were collected in order to detect the characteristics of pollen assemblages and their relationships with vegetation and climate in 16 forest communities located in 10 mountains in n...53 pollen traps and surface samples were collected in order to detect the characteristics of pollen assemblages and their relationships with vegetation and climate in 16 forest communities located in 10 mountains in northern China. The results show that 72% of the pollen taxa (80 taxa) are the same between the traps and the surface samples. The dominant taxa in the plant communities are consistent with the main pollen taxa in the pollen assemblages at the same sites. In Pinus plant communities, both Pinus pollen influx and concentration are higher, indicating the high pollen productivity and good pollen preservation ability of Pinus. In Picea and Abies plant communities, Picea and Abies have lower pollen influxes but higher concentrations, suggesting their low pollen productivities but better pollen preservation abilities. In Betula and Quercus plant communities, Betula and Quercus have higher pollen influxes but lower concentrations, revealing their high pollen productivities but poor pollen preservation abilities. The study of relationships between pollen and vegetation with discriminant analysis shows that pollen assemblages from both trap and surface samples can reflect the characteristics of different communities and distinguish different ecological areas, but surface samples can reflect the dominant components of communities much better than the traps. The study on correlations between pollen assemblages and climate with DCCA reveals that significant correlations exist between pollen assemblages and mean temperature of the coldest month (r = 0.84 for trap samples, r = 0.72 for surface samples), and then annual mean precipitation (r = 0.73 for trap samples, r = 0.71 for surface samples).展开更多
The Taiwan Strait is a transition zone between the East China Sea and the South China Sea with unique hydrology and a geographical environment that creates special marine community features.To analyze the spatial stru...The Taiwan Strait is a transition zone between the East China Sea and the South China Sea with unique hydrology and a geographical environment that creates special marine community features.To analyze the spatial structure and seasonal changes of the nekton assemblages in the Taiwan Strait,seasonal experimental trawl surveys were conducted during 2006-2007.The results showed that there were two assemblages in the area with different sets of species,and the average similarity within each group varies between 39.38% and 74.20%.By using multivariate statistical analysis and analyzing the distribution of dominant species,we found that the structures of the assemblages had obvious seasonal variation.The middle region from the Putian transect to the Xiamen transect could be considered a mixing area for the two assemblages.The analysis of the relationship between species assemblages and environmental factors indicated that temperature was the most important factor affecting the community structure in cold seasons,and 22.5°C and 17°C could be considered dividing lines for spring and winter,respectively.In warm seasons,the most important factor was water depth,but the relationship with depth was not as significant,with a correlation between 0.264 and 0.399.The seasonal changes of nekton assemblages basically reflected the dynamic currents in the Taiwan Strait.The south coastal assemblage extended to nearly the entire area of the Taiwan Strait along with a strong and intense warm current that shrinks in spring and winter when the southward intrusion of the cold Zhejiang-Fujian coastal current becomes stronger.The impact of shortterm and long-term environmental changes,such as extreme weather,global warming and human activity on nekton assemblages,had been recognized but need further research.Our study on nekton assemblages could be used as a baseline for measuring future changes.展开更多
The reconstruction of paleovegetation and paleoclimate requires an understanding of the relationships between surface pollen assemblages and modern vegetation and climate.Here,we analyzed the characteristics of surfac...The reconstruction of paleovegetation and paleoclimate requires an understanding of the relationships between surface pollen assemblages and modern vegetation and climate.Here,we analyzed the characteristics of surface pollen assemblages across different vegetation zones in the Tianshan Mountains.Using surface pollen analysis and vegetation sample surveys at 75 sites on the northern slopes of the Tianshan Mountains,we determined the correlation between the percentage of dominant pollen types and the corresponding vegetation cover.Redundancy analysis was used to investigate the relationships between surface pollen assemblages and environmental factors.Our results show that the Tianshan Mountains contain several distinct ecological regions,which can be divided into five main vegetation zones from low to high altitudes:mountain desert zone(Hutubi County(HTB):500-1300 m;Qitai County(QT):1000-1600 m),mountain steppe zone(HTB:1400-1600 m;QT:1650-1800 m),mountain forest zone(HTB:1650-2525 m;QT:1850-2450 m),subalpine meadow zone(HTB:2550-2600 m;QT:2500-2600 m),and alpine mat vegetation zone(HTB:2625-2700 m;QT:2625-2750 m).The surface pollen assemblages of different vegetation zones can accurately reflect the characteristics of the mountainous vegetation patterns on the northern slopes of the Tianshan Mountains when excluding the widespread occurrence of Chenopodiaceae,Artemisia,and Picea pollen.Both average annual precipitation(P_(ann))and annual average temperature(T_(ann))affect the distribution of surface pollen assemblages.Moreover,P_(ann) is the primary environmental factor affecting surface pollen assemblages in this region.A significant correlation exists between the pollen percentage and vegetation cover of Picea,Chenopodiaceae,Artemisia,and Asteraceae.Moreover,Picea,Chenopodiaceae,and Artemisia pollen are over-represented compared with their corresponding vegetation cover.The Asteraceae pollen percentage roughly reflects the distribution of a species within the local vegetation.These results have important implications for enhancing our understanding of the relationship between surface pollen assemblages and modern vegetation and climate.展开更多
Distribution characteristics of fish assemblages and environmental variation in emerged plant, floating-leaved plant and blank habitats were studied. Emergent plant habitat supported the greatest fish biomass, density...Distribution characteristics of fish assemblages and environmental variation in emerged plant, floating-leaved plant and blank habitats were studied. Emergent plant habitat supported the greatest fish biomass, density and body size, followed by floating-leaved plant habitat, and those of blank habitat was the lowest. Transparency of emergent plant habitat decreased during the period, but of blank habitat increased. Species number of dominant fish of emergent plant habitat compared to the others decreased from four species, i.e., Hemicculter leuciclus, Pseudobrama simoni, Carassius auratus and Ophicephalus argus in May to the single one, C. auratus in September. Those of blank habitat increased from two species, H. leuciclus and Pseudorasbora parva to four species, H. leuciclus, C. auratus, P. parva and O. argus. This result suggested that emergent plant with excessively high density could worsen habitat physical and chemical conditions, resulted in the fish’s emigration to unvegetated area. Those of floating-leaved plant habitat from two species, Cultrichthys erythropterus and P. simoni, changed into four species, C. erythropterus, P. simoni, H. leuciclus and P. parva. The increasing structure complexity and biomass of floating-leaved macrophyte promoted the increase of dominant fish species number with seasonal change. C. auratus, C. erythropterus and H. leuciclus displayed special preferences on emergent plant, floating-leaved plant and blank habitats respectively. Fish’s special habitat preference was determined by plant physical morphology, habitat characteristics and fish breeding habits.展开更多
Long-term data on diatom assemblages in a sediment core （60 cm） obtained from the Changjiang （Yangtze） River estuary were analyzed in order to assess the environmental changes that took place in the approximately ...Long-term data on diatom assemblages in a sediment core （60 cm） obtained from the Changjiang （Yangtze） River estuary were analyzed in order to assess the environmental changes that took place in the approximately 38 years （as determined by 210pb measurements）, i.e., between 1974 and 2012, of sediment accumulation. From the sediment core, 62 diatom taxa and genera were identified. The diatom biomass in the core generally increased beginning in the mid-1990s （core depth： 35 cm）, accompanied by a shift in the dominant species from Podosira stelliger and two species of Cyclotella （C. stylorum and C. striata） to Paralia sulcata, three species of Thalassiosira （ T. eccentria, I＂. oestrupii, and T. excentrica）, Actinoptychus undulates, and Thalassionema nitzschioides. The changes in both species diversity and abundance suggested that since the 1980s the estuary has undergone extensive eutrophication. This conclusion was supported by the increased proportion of planktonic species, another indicator of high nutrients inputs, in the Changjiang River estuary.展开更多
Bioavailability of nitrogen (N) and phosphorus (P) is known to affect marine phytoplankton physiology, thus influencing their primary productivity;and it’s of general interest to see how the N or/and P additions affe...Bioavailability of nitrogen (N) and phosphorus (P) is known to affect marine phytoplankton physiology, thus influencing their primary productivity;and it’s of general interest to see how the N or/and P additions affect the differently cell-sized phytoplankton assemblages. Data from the northern South China Sea showed that P addition increased up to 6 times of total chl a content within 24 h in the estuarine water;and N+P addition increased more than 20 times of chl a within 144 h in the pelagic water. The P addition powered 18.0% and 149% increase in the carbon fixation of larger (>3 μm) and smaller (展开更多
The focus of this study was to investigate the macroinvertebrate community in surface mine wetlands. Nine wetlands were sampled for macroinvertebrates from July 1993 through May 1994.These sites represented a range of...The focus of this study was to investigate the macroinvertebrate community in surface mine wetlands. Nine wetlands were sampled for macroinvertebrates from July 1993 through May 1994.These sites represented a range of physical,chemical, and biological parameters. Macroinvertebrates were found in all sites;a total of 14 orders, 40 families,and 70 genera were identified in the samples. Insects were the most common invertebrates,and most functional feeding groups were represented. Predators dominated with 63% of the taxa, followed by the collector/gathers with 20%,shredders 14%, and scrapers 3%. Sites differed in the number of taxa inhabiting them.Richness ranged from 10 genera to 52.The lowest richness was found in two seasonal wetlands that were dry for the majority of the year. A permanently flooded site with no water quality problems and a dense growth of aquatic plants had the highest richness.展开更多
The study on 82 surface soil pollen samples from different types of cultivated vegetations in central and southern parts of Hebei Province indicates that the pollen assem- blages from farmlands in the plain have not o...The study on 82 surface soil pollen samples from different types of cultivated vegetations in central and southern parts of Hebei Province indicates that the pollen assem- blages from farmlands in the plain have not only their own plant types, but also the pollen components from the nearby mountains. Arboreal pollen percentages and concentrations （dominated by Pinus） from farmlands in mountain area are higher than those in the plain, and it reduces gradually with the increasing distance away from the mountains. Taking Pinus pollen in Taihang Mountains as an example, its content is 20%-30%, 10%-20%, 20%-30% and below 16% respectively for the samples from the area of 0-50, 50-100, 100-150 and more than 150 km away from the east Taihang Mountains. The increase of Pinus pollen proportion in the central plain is probably related to the fohn effect. The spatial variation of AP from mountains to the plain in Hebei Province may be similar to the forests clearance by human activities in the early historical period. Shrubby pollen proportion is small both in mountains and in the plain, but their major components are different. Elaeagnaceae, Corylus, Ostryopsis and Oleaceae are common in mountain areas, while there are relatively high contents of Rosaceae and Vitaceae in the plain. Herbs content in the plain （about 60%） is 15% higher than that in mountains, among which the Cereals and Cruciferae pollen percentages are 5% and 2% higher respectively. Artemisia pollen percentage in the plain is lower than that in mountains. Since the human activities are weaker in mountains compared with that in the plain, the general trend is that Chenopodiaceae pollen increases from mountains to the plain gradually, reflecting the raising intensity of human activities. The fern spores of Selaginella sinensis in mountains are higher than that in the plain, but it still reaches to about 7% in the plain. The fern spores of Selaginella sinensis are not prone to be spread by wind, indicating that those in the surface soil of the plain may be carried by river water from mountains during the deposition of the plain.展开更多
The spatio-temporal patterns of macrofaunal fouling assemblages were quantitatively investigated in the nearshore waters of the South China Sea.The work was undertaken by deploying seasonal panels at two sites(H-site,...The spatio-temporal patterns of macrofaunal fouling assemblages were quantitatively investigated in the nearshore waters of the South China Sea.The work was undertaken by deploying seasonal panels at two sites(H-site,L-site) for one year,and the fouling communities on the panels were examined and analyzed.The results indicated that species composition of assemblages was obviously different between the two sites.At both sites the assemblages were characteristic with solitary dominant species throughout the year,with Amphibalanus reticulates dominating at H-site and Hydroides elegans at L-site.Shannon index and biomass of the assemblages varied with depth and season at both sites.At H-site the total biomass in summer and autumn were significantly higher than those in spring and winter,while at L-site the assemblage biomass also differed significantly among the four seasons,and the greatest biomass occurred at the depth of 2.0 m in winter.The abundance of all seasonal samples in non-metric multidimensional scaling was clustered as one group at L-site and three groups at H-site.The environmental factors were more likely to be related to the variation of fouling assemblages.Furthermore,it also suggests that in tropical seas the integrated adaptability would qualify a species for dominating a fouling assemblage despite its short life cycle,rather than the usually assumed only species with long life span.This study reveals the complexity and characteristic dynamics of macrofaunal fouling assemblages in the tropical habitats,and the results would provide valuable knowledge for biodiversity and antifouling research.展开更多
The spatial distribution and community structure of the fishes were studied at different depths and sites along the Jordanian coast in seagrass habitat. A total of 37,034 fishes were counted representing 132 species b...The spatial distribution and community structure of the fishes were studied at different depths and sites along the Jordanian coast in seagrass habitat. A total of 37,034 fishes were counted representing 132 species belonging to 35 families observed during visual census in three sites (average of 4741.6 fish per transect). Out of the 132 species encountered, 5 species of them including Neopomacentrus miryae Lethrinus borbonicus, Pseudanthias squamipinnis, Lethrinus variegatus, Siganus rivulatus accounted for 57.7% of all individuals. Fishes were most abundant and significantly higher at 12 m depths (mean N = 2889.6) in comparison with shallow 6m depth (mean = 1225.3 with (p = 0.0218). This may be attributed to many plank-tivorous fishes that inhabit this depth such as P. squampinnis, Paracheilinus octotaenia, Chromis pelloura, Decapterus macarellus, and Cirrhilabrus rubriventralis probably with high abundance of plankton at 12 m depth than 6 m. The number of species was significantly higher in Phosphate Loading Berth (PLB;mean S = 54.7) than in Hotels area site (HA;mean S = 12.8) with (p = 0.0002) and Tala Bay site (TB;mean S = 31) with (p = 0.0484). This may be due to higher hard coral cover at Phophate Loading Berth.展开更多
The East China Sea Shelf Basin generated a series of back-arc basins with thick successions of marine-and terrestrial-facies sediments during Cenozoic.It is enriched with abundant oil and gas resources and is of great...The East China Sea Shelf Basin generated a series of back-arc basins with thick successions of marine-and terrestrial-facies sediments during Cenozoic.It is enriched with abundant oil and gas resources and is of great significance to the petroleum exploration undertakings.Therein,the Lishui Sag formed fan delta,fluvial delta and littoral-to-neritic facies sediments during Paleocene–Eocene,and the research on its sedimentary environment and sediment source was controversial.This study analyzed the paleontological combination characteristics,and conducted a source-to-sink comparative analysis to restore the sedimentary environment and provenance evolution of the Lishui Sag during Paleocene–Eocene based on the integration of detrital zircon U-Pb age spectra patterns with paleontological assemblages.The results indicated that Lishui Sag was dominated by littoral and neritic-facies environment during time corroborated by large abundance of foraminifera,calcareous nannofossils and dinoflagellates.Chronological analysis of detrital zircon U-Pb revealed that there were significant differences in sediment sources between the east and west area of the Lishui Sag.The western area was featured by deeper water depths in the Paleocene–Eocene,and the sediment was characterized by a single Yanshanian peak of zircon U-Pb age spectra,and mainly influenced from Yanshanian magmatic rocks of South China Coast and the surrounding paleo-uplifts.However,its eastern area partly showed Indosinian populations.In particular,the upper Eocene Wenzhou sediments were featured by increasingly plentiful Precambrian zircons in addition to the large Indosinian-Yanshanian peaks,indicating a possible impact from the Yushan Low Uplift to the east.Therefore,it is likely that the eastern Lishui Sag generated large river systems as well as deltas during time.Due to the Yuquan Movement,the Lishui Sag experienced uplifting and exhumation in the late stage of the late Eocene and was not deposited with sediments until Miocene.Featured by transitional-facies depositions of Paleocene–Eocene,the Lishui Sag thus beared significant potential for source rock and oil-gas reservoir accumulation.展开更多
Background: Vegetation distribution maps are of great significance for nature protection and management. In diverse tropical forests, accurate spatial mapping of vegetation types is challenging;the high species divers...Background: Vegetation distribution maps are of great significance for nature protection and management. In diverse tropical forests, accurate spatial mapping of vegetation types is challenging;the high species diversity and abundance of rare species challenge classification concepts, while remote sensing signals may not vary systematically with species composition, complicating the technical capability for delineating vegetation types in the landscape.Methods: We used a combination of field-based compositional data and their relations to environmental variables to predict the distribution of forest types in the Wuzhishan National Natural Reserve(WNNR), Hainan Island,China, using multivariate regression trees(MRT). The MRT was based on arboreal vegetation composition in 132plots of 20 m×20 m with a regular spacing of 1 km. Apart from the MRT, non-metric multidimensional scaling(NMDS) was used to evaluate vegetation-environment relationships.Results: The MRT model worked best when using 14 key environmental variables including topography, climate,latitude and soil, although the difference with the simpler model including only topographical variables was small. The full model classified the 132 plots into 3 vegetation types, 6 formation groups, 20 formations and 65associations at different hierarchical syntaxonomic levels. This model was the basis for forest vegetation maps for the WNNR. MRT and NMDS showed that elevation was the main driving force for the distribution of vegetation types and formation groups. Climate, latitude, and soil(especially available P), together with topographic variables, all influenced the distribution of formations and associations.Conclusions: While elevation determines forest-type distributions, lower-level syntaxonomic forest classes respond to the topographic diversity typical for mountains. Apart from providing the first detailed forest vegetation map for any part of WNNR, we show how, in spite of limitations, MRT with existing environmental data can be a useful method for mapping diverse and remote tropical forests.展开更多
基金financial support from the National Natural Science Foundation of China(Grant Nos.U23B20155 and 42202140)the Science and Technology Innovation Program of Hunan Province(2023RC1021)+1 种基金the China Geological Survey(DD20221659)the Science and Technology Bureau,Changsha,China(kq2208261)。
文摘The marine-continental transitional shale of the Upper Permian Longtan Formation is widely distributed in Hunan and shows significant exploration potential.Frequent changes in lithofacies have however notably influenced the shale gas enrichment.The strata of the Longtan Formation in the Shaoyang Depression,central Hunan,were taken as the study object for this project.Three lithofacies assemblages were identified:shale interbedded with sandstone layer(SAL),sandstone interbedded with shale layer(ASL)and laminated shale layer(LSL).The SAL shale shows significant variability in hydrocarbon generation potential,which leads to shale gas characterized by'hydrocarbon generation in high total organic carbon(TOC)shale,retention in low TOC shale and accumulation in sandstone'.The ASL shale,influenced by the redox conditions of the depositional environment,shows a lower concentration of organic matter.This results in an enrichment model of'hydrocarbon generation and accumulation in shale,with sealing by sandstone'.The laminar structure of LSL shale causes both quartz and clay minerals to control the reservoir.Shale gas is characterized by'hydrocarbon generation in mud laminae,retention and accumulation in silty laminae,with multiple intra-source migration paths'.In the marine-continental transitional shale gas system,the enrichment intervals of different types of shale gas reservoirs exhibit significant variability.
基金supported by the National Natural Science Foundation of China(Nos.52034009 and 52174093)the Fundamental Research Funds for the Central Universities(Nos.2024ZKPYNY01,2023ZKPYNY03,and 2023YQTD02).
文摘To reveal the deterioration mechanism of coal-rock assemblages under chemical corrosion and dynamic loading,chemical corrosion and dynamic impact experiments were conducted.Under different chemical corrosion conditions,the weakening characteristics,observable characteristics,softening characteristics of the dynamic parameters,dynamic failure characteristics,dynamic failure forms and dynamic microscopic characteristics were analyzed.Under each corrosion condition,the dynamic elastic modulus,dynamic deformation modulus and dynamic peak intensity tended to decrease with immersing time.The dynamic elastic modulus,dynamic deformation modulus and dynamic peak intensity exhibited an inverted U-shaped trend.Under dynamic impact,the failure process of acidly corroded samples can be divided into the following stages:the initial stage,elastic energy accumulation stage,local failure of coal and secondary rock crack expansion stage,coal fragment ejection stage,rock spalling stage and complete instability stage.Under dynamic impact,failure modes exist:coal crushing failure,rock fragmenting failure,rock splitting failure and full splitting failure.After impact failure,sample fragments are distributed in powder,granular,cone and block forms.Based on Zhu-Wang-Tang nonlinear viscoelastic properties,a model considering chemical corrosion and impact damage was proposed.The combined effects of chemical and impact-induced damage on the dynamic mechanical properties of coal-rock assemblages were systematically analyzed.
基金Supported by the National Natural Science Foundation of China(U22B6002)National Project for Oil and Gas Technology(2016ZX05-004)CNPC Science and Technology Project(2023ZZ02).
文摘The Ediacaran–Ordovician strata within three major marine basins(Tarim,Sichuan,and Ordos)in China are analyzed.Based on previous studies focusing on the characteristics of the Neoproterozoic–Cambrian strata within the three major basins(East Siberian,Oman,and Officer in Australia)overseas,the carbonate–evaporite assemblages in the target interval are divided into three types:intercalated carbonate and gypsum salt,interbedded carbonate and gypsum salt,and coexisted carbonate,gypsum salt and clastic rock.Moreover,the concept and definition of the carbonate-evaporite assemblage are clarified.The results indicate that the oil and gas in the carbonate-evaporite assemblage are originated from two types of source rocks:shale and argillaceous carbonate,and confirmed the capability of gypsum salt in the saline environment to drive the source rock hydrocarbon generation.The dolomite reservoirs are classified in two types:gypseous dolomite flat,and grain shoalµbial mound.This study clarifies that the penecontemporaneous or epigenic leaching of atmospheric fresh water mainly controlled the large-scale development of reservoirs.Afterwards,burial dissolution transformed and reworked the reservoirs.The hydrocarbon accumulation in carbonate-evaporite assemblage can be categorized into eight sub-models under three models(sub-evaporite hydrocarbon accumulation,supra-evaporite hydrocarbon accumulation,and inter-evaporite hydrocarbon accumulation).As a result,the Cambrian strata in the Tazhong Uplift North Slope,Maigaiti Slope and Mazatag Front Uplift Zone of the Tarim Basin,the Cambrian strata in the eastern-southern area of the Sichuan Basin,and the inter-evaporite Ma-4 Member of Ordovician in the Ordos Basin,China,are defined as favorable targets for future exploration.
基金The China Scholarship Council under contract No.202308310175the China Postdoctoral Science Foundation under contract No.E-6005-00-0042-39+6 种基金Postdoctoral Fellowship Program of CPSF under contract No. GZC20231539the Jiangsu Haizhou Bay National Sea Ranching Demonstration Project under contract No. D–8005–18–0188Shanghai Municipal Science and Technology Commission Local Capacity Construction Project under contract No. 21010502200the Science Foundation for Youths of Jiangsu ProvinceChina under contract No. BK20170438the Science and Technology Projects in Nantong under contract No. JC2018014the Social Livelihood Key Projects of Nantong under contract No. MS22021015。
文摘To better understand the community patterns mediated by connectivity in artificial reefs of coastal areas, it is necessary to understand the distribution and coexistence of organisms with artificial reefs area and adjacent waters. This study was conducted to examine main catches assemblages collected by trawls in Haizhou Bay,which included five habitats: the artificial reef area(AR), aquaculture area(AA), natural area(NA), estuary area(EA) and comprehensive effect area(CEA). The result shows that the total abundances of species in the five habitats were highly different(univariate PERMANOVA: P = 0.001, n = 24), but some species were also unique in their habitat(e.g. Scapharca subcrenata and Glossaulax didyma in AA). The body size distribution of specific species between habitats are different. For Collichthys lucidus, their body size in AR(14.63 cm ± 1.64 cm) and EA(14.3 cm ± 0.85 cm) is higher than that in NA(10.65 cm ± 1.64 cm), CEA(11.28 cm ± 1.85 cm) and AA(12.1 cm ±0.43 cm), which indicates the potential connection from AR to EA mediated by their adult population. We concluded that artificial reefs in AR can be considered key components that have the ability to support species assemblages in adjacent habitats. This study has implications for the conservation and monitoring of species assemblages in coastal areas in terms of that artificial reefs can be applied in different stages of habitat protection implementation and in different combinations of scenarios.
基金supported by the National Key Research and Development Plan (2017YFC0601400)SDUST Research Fund (2018TDJH101)the National Natural Science Foundation of China (41402086, 272172)
文摘Coal and oil shale are two common sedimentary energy sources which are often symbiotically developed in M esozoic- Cenozoic continental fault basins. However, the mechanisms and characteristics of the symbiotic development are not yet clearly known. In this research study, the typical continental fault basins of eastern China were chosen as examples for the purpose of conducting an examination of the coal and oil shale symbiotic assemblage types, genetic environmental differences, and transformation mechanisms, as well as the development and occurrence characteristics o f different assemblage types. Through a large number of investigations, systematic experimental testing, and sequence stratigraphy studies, the following conclusions were obtained:(1) There were five types of coal and oil shale symbiotic assemblages observed in the continental fault basins,(2) The development of coal and oil shale deposits requires a warm and humid climate, stable structure, abundant organic matter supply, a certain water depth, and a lower terrestrial source debris supply. The observed differences were that the water depth conditions were diversified in the study area, as well as the sources, types, and content of the organic matter.(3) The rapid transformations of the coal and oil shale genetic environments were mainly controlled by the tectonic settings and climatic conditions, which were determined to control the changes in the water depths, salinity,redox conditions, and lake productivity of the genetic environments. Also, in the symbiotic assemblages, genetic environment changes had induced the development of oil shale deposits, which gradually evolved into coal genetic environments.(4) In the isochronous sequence stratigraphic framework of the coal and oil shale symbiotic assemblages, the lake expansion system tracts (EST) were determined to be the most beneficial to the growth o f all the types of assemblages and were characterized by more assemblage development phases and smaller bed thicknesses. From the early to the late stages of the EST, and from the lakesides to lake centers, the thicknesses of the coal seams in the symbiotic assemblages showed trends of thinning, while the thicknesses of the oil shale deposits exhibited increasing trends. The early stages of high stand system tracts were found to be beneficial to the development of the symbiotic assemblages of coal seams overlying the oil shale. This tract type generally presented large bed thicknesses and distribution ranges. The low stand system tract and the late high stand system tract were determined to be unconducive to the development of the symbiotic assemblages.
基金funded by the National Basic Research Program of China (2013CB429903)the National Natural Science Foundation of China (41201248, 31170496)
文摘Shrub presence has an important effect on the structuring of ground beetles in desert ecosystems. In this study, in order to determine how shrubs and different species influence ground beetle assemblages in a sandy desert scrubland dominated by two different shrub species, namely Calligonum mongolicum and Nitraria sphaerocarpa, we sampled the ground beetles using pitfall traps during spring, summer and autumn in 2012. At the community level, the activity density of the ground beetles was shown to be significantly higher under shrubs than in intershrub bare habitats in spring; but an opposite pattern occurred in autumn, suggesting the presence of sea- son-specific shrub effects on the activity density of the ground beetles. Meanwhile, at the trophic group level, the activity density and species richness of predators were significantly greater under shrubs than in intershrub bare habitats in spring, whereas an opposite trend occurred on the activity density in autumn. N. sphaerocarpa shrubs had a positive effect on the activity density of herbivores in the three seasons, and C. mongolicum shrubs had a positive effect on the activity density of detritivores in spring and autumn. At the species level, more Microdera sp. was captured under shrubs than in intershrub bare habitats in spring. During the same time, we also found that C. mongolicum shrubs had a positive effect on Blaps gobiensis in spring, Carabus sp. in autumn, and Tentyria sp. in spring and autumn, and N. sphaerocarpa shrubs had a positive effect on Cyphogenia chinensis, Sternoplax setosa in spring and summer, and Curculionidae sp. 1 in summer and autumn. The study results suggest that shrub presence, shrub species and season variation are important factors for ground beetle assemblages in this desert ecosystem, but the responses of beetles differed among trophic and taxonomic levels.
基金supported by the Exploration and Development Research Institute of the Jilin Oilfield Company Ltd. (Grant No.JLYT-YJY-2013-JS-305)
文摘The pollen and spores found in the Early Cretaceous strata of two cores from the Shuangliao Fault Depression were studied systematically, and two palynological assemblages have been recognized. Assemblage I from the Yingcheng Formation is named Paleoconiferus-Pinuspollenites; the assemblage is characterized by an extremely high content of Paleoconifer pollen. Assemblage II from Member 1 of the Denglouku Formation is named Cicatricosisporites-Cyathidites-Pinuspollenites; the assemblage is characterized by the abundant presence of Laevigati spores, but less Paleoconifer pollen. According to the palynological data and zircon U-Pb dating, the geological age of the Yingcheng Formation is thought to be Aptian-Albian, and that of the Denglouku Formation is thought to be Early Albian. On the basis of the composition of each assemblage, we can infer that during the depositional period of the Yingcheng Formation, the paleovegetation was mainly conifer forest, the paleoclimate was consistent with the temperate climate of today, and the paleoenvironment was humid feature. During the depositional period of Member 1 of the Denglouku Formation, the paleovegetation was mainly conifer forest and shrubs, the paleoclimate was consistent with the subtropical climate of today, and the paleoenvironment was humid. The results significantly improve our understanding of the stratigraphy in the Shuangliao Fault Depression, provide biostratigraphic evidence for the division and correlation of Early Cretaceous strata in the Shuangliao Fault Depression, and provide new data for analyzing paleovegetation and paleoclimate in the Songliao Basin.
基金Preliminary Special Foundation for National Key Basic Research of China, No.2003CCA01800Key National Natural Science Foundation of China, No.40730103+3 种基金National Natural Science Foundation of China, No.40672107 No.40571166Natural Science Foundation of Hebei Province, No.D2008000186 No.D2009000300
文摘53 pollen traps and surface samples were collected in order to detect the characteristics of pollen assemblages and their relationships with vegetation and climate in 16 forest communities located in 10 mountains in northern China. The results show that 72% of the pollen taxa (80 taxa) are the same between the traps and the surface samples. The dominant taxa in the plant communities are consistent with the main pollen taxa in the pollen assemblages at the same sites. In Pinus plant communities, both Pinus pollen influx and concentration are higher, indicating the high pollen productivity and good pollen preservation ability of Pinus. In Picea and Abies plant communities, Picea and Abies have lower pollen influxes but higher concentrations, suggesting their low pollen productivities but better pollen preservation abilities. In Betula and Quercus plant communities, Betula and Quercus have higher pollen influxes but lower concentrations, revealing their high pollen productivities but poor pollen preservation abilities. The study of relationships between pollen and vegetation with discriminant analysis shows that pollen assemblages from both trap and surface samples can reflect the characteristics of different communities and distinguish different ecological areas, but surface samples can reflect the dominant components of communities much better than the traps. The study on correlations between pollen assemblages and climate with DCCA reveals that significant correlations exist between pollen assemblages and mean temperature of the coldest month (r = 0.84 for trap samples, r = 0.72 for surface samples), and then annual mean precipitation (r = 0.73 for trap samples, r = 0.71 for surface samples).
基金The Scientific Research Foundation of Third Institute of Oceanography,SOA under contract No.2016011the International Cooperation and Implementation Project of the State Oceanic Administration under contract No.2200207Chinese Offshore Investigation and Assessment under contract Nos 908-02-01-02 and 908-02-04-01
文摘The Taiwan Strait is a transition zone between the East China Sea and the South China Sea with unique hydrology and a geographical environment that creates special marine community features.To analyze the spatial structure and seasonal changes of the nekton assemblages in the Taiwan Strait,seasonal experimental trawl surveys were conducted during 2006-2007.The results showed that there were two assemblages in the area with different sets of species,and the average similarity within each group varies between 39.38% and 74.20%.By using multivariate statistical analysis and analyzing the distribution of dominant species,we found that the structures of the assemblages had obvious seasonal variation.The middle region from the Putian transect to the Xiamen transect could be considered a mixing area for the two assemblages.The analysis of the relationship between species assemblages and environmental factors indicated that temperature was the most important factor affecting the community structure in cold seasons,and 22.5°C and 17°C could be considered dividing lines for spring and winter,respectively.In warm seasons,the most important factor was water depth,but the relationship with depth was not as significant,with a correlation between 0.264 and 0.399.The seasonal changes of nekton assemblages basically reflected the dynamic currents in the Taiwan Strait.The south coastal assemblage extended to nearly the entire area of the Taiwan Strait along with a strong and intense warm current that shrinks in spring and winter when the southward intrusion of the cold Zhejiang-Fujian coastal current becomes stronger.The impact of shortterm and long-term environmental changes,such as extreme weather,global warming and human activity on nekton assemblages,had been recognized but need further research.Our study on nekton assemblages could be used as a baseline for measuring future changes.
基金supported by the National Natural Science Foundation of China(42071102).
文摘The reconstruction of paleovegetation and paleoclimate requires an understanding of the relationships between surface pollen assemblages and modern vegetation and climate.Here,we analyzed the characteristics of surface pollen assemblages across different vegetation zones in the Tianshan Mountains.Using surface pollen analysis and vegetation sample surveys at 75 sites on the northern slopes of the Tianshan Mountains,we determined the correlation between the percentage of dominant pollen types and the corresponding vegetation cover.Redundancy analysis was used to investigate the relationships between surface pollen assemblages and environmental factors.Our results show that the Tianshan Mountains contain several distinct ecological regions,which can be divided into five main vegetation zones from low to high altitudes:mountain desert zone(Hutubi County(HTB):500-1300 m;Qitai County(QT):1000-1600 m),mountain steppe zone(HTB:1400-1600 m;QT:1650-1800 m),mountain forest zone(HTB:1650-2525 m;QT:1850-2450 m),subalpine meadow zone(HTB:2550-2600 m;QT:2500-2600 m),and alpine mat vegetation zone(HTB:2625-2700 m;QT:2625-2750 m).The surface pollen assemblages of different vegetation zones can accurately reflect the characteristics of the mountainous vegetation patterns on the northern slopes of the Tianshan Mountains when excluding the widespread occurrence of Chenopodiaceae,Artemisia,and Picea pollen.Both average annual precipitation(P_(ann))and annual average temperature(T_(ann))affect the distribution of surface pollen assemblages.Moreover,P_(ann) is the primary environmental factor affecting surface pollen assemblages in this region.A significant correlation exists between the pollen percentage and vegetation cover of Picea,Chenopodiaceae,Artemisia,and Asteraceae.Moreover,Picea,Chenopodiaceae,and Artemisia pollen are over-represented compared with their corresponding vegetation cover.The Asteraceae pollen percentage roughly reflects the distribution of a species within the local vegetation.These results have important implications for enhancing our understanding of the relationship between surface pollen assemblages and modern vegetation and climate.
文摘Distribution characteristics of fish assemblages and environmental variation in emerged plant, floating-leaved plant and blank habitats were studied. Emergent plant habitat supported the greatest fish biomass, density and body size, followed by floating-leaved plant habitat, and those of blank habitat was the lowest. Transparency of emergent plant habitat decreased during the period, but of blank habitat increased. Species number of dominant fish of emergent plant habitat compared to the others decreased from four species, i.e., Hemicculter leuciclus, Pseudobrama simoni, Carassius auratus and Ophicephalus argus in May to the single one, C. auratus in September. Those of blank habitat increased from two species, H. leuciclus and Pseudorasbora parva to four species, H. leuciclus, C. auratus, P. parva and O. argus. This result suggested that emergent plant with excessively high density could worsen habitat physical and chemical conditions, resulted in the fish’s emigration to unvegetated area. Those of floating-leaved plant habitat from two species, Cultrichthys erythropterus and P. simoni, changed into four species, C. erythropterus, P. simoni, H. leuciclus and P. parva. The increasing structure complexity and biomass of floating-leaved macrophyte promoted the increase of dominant fish species number with seasonal change. C. auratus, C. erythropterus and H. leuciclus displayed special preferences on emergent plant, floating-leaved plant and blank habitats respectively. Fish’s special habitat preference was determined by plant physical morphology, habitat characteristics and fish breeding habits.
基金Supported by the National Basic Research Program of China(973 Program)(No.2010CB428706)the Funds for Creative Research Groups of China(No.41121064)
文摘Long-term data on diatom assemblages in a sediment core （60 cm） obtained from the Changjiang （Yangtze） River estuary were analyzed in order to assess the environmental changes that took place in the approximately 38 years （as determined by 210pb measurements）, i.e., between 1974 and 2012, of sediment accumulation. From the sediment core, 62 diatom taxa and genera were identified. The diatom biomass in the core generally increased beginning in the mid-1990s （core depth： 35 cm）, accompanied by a shift in the dominant species from Podosira stelliger and two species of Cyclotella （C. stylorum and C. striata） to Paralia sulcata, three species of Thalassiosira （ T. eccentria, I＂. oestrupii, and T. excentrica）, Actinoptychus undulates, and Thalassionema nitzschioides. The changes in both species diversity and abundance suggested that since the 1980s the estuary has undergone extensive eutrophication. This conclusion was supported by the increased proportion of planktonic species, another indicator of high nutrients inputs, in the Changjiang River estuary.
文摘Bioavailability of nitrogen (N) and phosphorus (P) is known to affect marine phytoplankton physiology, thus influencing their primary productivity;and it’s of general interest to see how the N or/and P additions affect the differently cell-sized phytoplankton assemblages. Data from the northern South China Sea showed that P addition increased up to 6 times of total chl a content within 24 h in the estuarine water;and N+P addition increased more than 20 times of chl a within 144 h in the pelagic water. The P addition powered 18.0% and 149% increase in the carbon fixation of larger (>3 μm) and smaller (
文摘The focus of this study was to investigate the macroinvertebrate community in surface mine wetlands. Nine wetlands were sampled for macroinvertebrates from July 1993 through May 1994.These sites represented a range of physical,chemical, and biological parameters. Macroinvertebrates were found in all sites;a total of 14 orders, 40 families,and 70 genera were identified in the samples. Insects were the most common invertebrates,and most functional feeding groups were represented. Predators dominated with 63% of the taxa, followed by the collector/gathers with 20%,shredders 14%, and scrapers 3%. Sites differed in the number of taxa inhabiting them.Richness ranged from 10 genera to 52.The lowest richness was found in two seasonal wetlands that were dry for the majority of the year. A permanently flooded site with no water quality problems and a dense growth of aquatic plants had the highest richness.
基金Key National Natural Science Foundation of China, No.40730103 National Natural Science Foundation of China No. 40571166 and 40672107 Hebei Natural Science Foundation No.D2008000186, No.D2009000300
文摘The study on 82 surface soil pollen samples from different types of cultivated vegetations in central and southern parts of Hebei Province indicates that the pollen assem- blages from farmlands in the plain have not only their own plant types, but also the pollen components from the nearby mountains. Arboreal pollen percentages and concentrations （dominated by Pinus） from farmlands in mountain area are higher than those in the plain, and it reduces gradually with the increasing distance away from the mountains. Taking Pinus pollen in Taihang Mountains as an example, its content is 20%-30%, 10%-20%, 20%-30% and below 16% respectively for the samples from the area of 0-50, 50-100, 100-150 and more than 150 km away from the east Taihang Mountains. The increase of Pinus pollen proportion in the central plain is probably related to the fohn effect. The spatial variation of AP from mountains to the plain in Hebei Province may be similar to the forests clearance by human activities in the early historical period. Shrubby pollen proportion is small both in mountains and in the plain, but their major components are different. Elaeagnaceae, Corylus, Ostryopsis and Oleaceae are common in mountain areas, while there are relatively high contents of Rosaceae and Vitaceae in the plain. Herbs content in the plain （about 60%） is 15% higher than that in mountains, among which the Cereals and Cruciferae pollen percentages are 5% and 2% higher respectively. Artemisia pollen percentage in the plain is lower than that in mountains. Since the human activities are weaker in mountains compared with that in the plain, the general trend is that Chenopodiaceae pollen increases from mountains to the plain gradually, reflecting the raising intensity of human activities. The fern spores of Selaginella sinensis in mountains are higher than that in the plain, but it still reaches to about 7% in the plain. The fern spores of Selaginella sinensis are not prone to be spread by wind, indicating that those in the surface soil of the plain may be carried by river water from mountains during the deposition of the plain.
基金supported by the National Natural Science Foundation of China(Nos.31660128,31360105 and 31160098)the Hainan University(Nos.kypd 1046 and Hdcxcyxm201715)
文摘The spatio-temporal patterns of macrofaunal fouling assemblages were quantitatively investigated in the nearshore waters of the South China Sea.The work was undertaken by deploying seasonal panels at two sites(H-site,L-site) for one year,and the fouling communities on the panels were examined and analyzed.The results indicated that species composition of assemblages was obviously different between the two sites.At both sites the assemblages were characteristic with solitary dominant species throughout the year,with Amphibalanus reticulates dominating at H-site and Hydroides elegans at L-site.Shannon index and biomass of the assemblages varied with depth and season at both sites.At H-site the total biomass in summer and autumn were significantly higher than those in spring and winter,while at L-site the assemblage biomass also differed significantly among the four seasons,and the greatest biomass occurred at the depth of 2.0 m in winter.The abundance of all seasonal samples in non-metric multidimensional scaling was clustered as one group at L-site and three groups at H-site.The environmental factors were more likely to be related to the variation of fouling assemblages.Furthermore,it also suggests that in tropical seas the integrated adaptability would qualify a species for dominating a fouling assemblage despite its short life cycle,rather than the usually assumed only species with long life span.This study reveals the complexity and characteristic dynamics of macrofaunal fouling assemblages in the tropical habitats,and the results would provide valuable knowledge for biodiversity and antifouling research.
文摘The spatial distribution and community structure of the fishes were studied at different depths and sites along the Jordanian coast in seagrass habitat. A total of 37,034 fishes were counted representing 132 species belonging to 35 families observed during visual census in three sites (average of 4741.6 fish per transect). Out of the 132 species encountered, 5 species of them including Neopomacentrus miryae Lethrinus borbonicus, Pseudanthias squamipinnis, Lethrinus variegatus, Siganus rivulatus accounted for 57.7% of all individuals. Fishes were most abundant and significantly higher at 12 m depths (mean N = 2889.6) in comparison with shallow 6m depth (mean = 1225.3 with (p = 0.0218). This may be attributed to many plank-tivorous fishes that inhabit this depth such as P. squampinnis, Paracheilinus octotaenia, Chromis pelloura, Decapterus macarellus, and Cirrhilabrus rubriventralis probably with high abundance of plankton at 12 m depth than 6 m. The number of species was significantly higher in Phosphate Loading Berth (PLB;mean S = 54.7) than in Hotels area site (HA;mean S = 12.8) with (p = 0.0002) and Tala Bay site (TB;mean S = 31) with (p = 0.0484). This may be due to higher hard coral cover at Phophate Loading Berth.
基金The National Natural Science Foundation of China under contract Nos 42076066 and 92055203。
文摘The East China Sea Shelf Basin generated a series of back-arc basins with thick successions of marine-and terrestrial-facies sediments during Cenozoic.It is enriched with abundant oil and gas resources and is of great significance to the petroleum exploration undertakings.Therein,the Lishui Sag formed fan delta,fluvial delta and littoral-to-neritic facies sediments during Paleocene–Eocene,and the research on its sedimentary environment and sediment source was controversial.This study analyzed the paleontological combination characteristics,and conducted a source-to-sink comparative analysis to restore the sedimentary environment and provenance evolution of the Lishui Sag during Paleocene–Eocene based on the integration of detrital zircon U-Pb age spectra patterns with paleontological assemblages.The results indicated that Lishui Sag was dominated by littoral and neritic-facies environment during time corroborated by large abundance of foraminifera,calcareous nannofossils and dinoflagellates.Chronological analysis of detrital zircon U-Pb revealed that there were significant differences in sediment sources between the east and west area of the Lishui Sag.The western area was featured by deeper water depths in the Paleocene–Eocene,and the sediment was characterized by a single Yanshanian peak of zircon U-Pb age spectra,and mainly influenced from Yanshanian magmatic rocks of South China Coast and the surrounding paleo-uplifts.However,its eastern area partly showed Indosinian populations.In particular,the upper Eocene Wenzhou sediments were featured by increasingly plentiful Precambrian zircons in addition to the large Indosinian-Yanshanian peaks,indicating a possible impact from the Yushan Low Uplift to the east.Therefore,it is likely that the eastern Lishui Sag generated large river systems as well as deltas during time.Due to the Yuquan Movement,the Lishui Sag experienced uplifting and exhumation in the late stage of the late Eocene and was not deposited with sediments until Miocene.Featured by transitional-facies depositions of Paleocene–Eocene,the Lishui Sag thus beared significant potential for source rock and oil-gas reservoir accumulation.
基金financially supported by National Key R&D Program of China(2021YFD220040403 and 2021YFD220040304)the China Scholarship Council(202107565021).
文摘Background: Vegetation distribution maps are of great significance for nature protection and management. In diverse tropical forests, accurate spatial mapping of vegetation types is challenging;the high species diversity and abundance of rare species challenge classification concepts, while remote sensing signals may not vary systematically with species composition, complicating the technical capability for delineating vegetation types in the landscape.Methods: We used a combination of field-based compositional data and their relations to environmental variables to predict the distribution of forest types in the Wuzhishan National Natural Reserve(WNNR), Hainan Island,China, using multivariate regression trees(MRT). The MRT was based on arboreal vegetation composition in 132plots of 20 m×20 m with a regular spacing of 1 km. Apart from the MRT, non-metric multidimensional scaling(NMDS) was used to evaluate vegetation-environment relationships.Results: The MRT model worked best when using 14 key environmental variables including topography, climate,latitude and soil, although the difference with the simpler model including only topographical variables was small. The full model classified the 132 plots into 3 vegetation types, 6 formation groups, 20 formations and 65associations at different hierarchical syntaxonomic levels. This model was the basis for forest vegetation maps for the WNNR. MRT and NMDS showed that elevation was the main driving force for the distribution of vegetation types and formation groups. Climate, latitude, and soil(especially available P), together with topographic variables, all influenced the distribution of formations and associations.Conclusions: While elevation determines forest-type distributions, lower-level syntaxonomic forest classes respond to the topographic diversity typical for mountains. Apart from providing the first detailed forest vegetation map for any part of WNNR, we show how, in spite of limitations, MRT with existing environmental data can be a useful method for mapping diverse and remote tropical forests.
