The genetic environmental transformation mechanism of coal and oil shale deposits in eastern China’s continental fault basins and the developmental characteristics of the area’s symbiotic assemblages——taking Huangxian Basin as an example

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.

Hydrocarbon accumulation in deep ancient carbonate-evaporite assemblages

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 shoal&microbial 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.

Miocene paleoenvironmental evolution based on benthic foraminiferal assemblages in the Lufeng Sag, northern South China Sea

The Miocene epoch marks the most crucial period during the Cenozoic cooling trend, characterized by the Middle Miocene Climatic Optimum(MMCO) and a series of short–lived cooling events(Miocene isotope events).To understand the paleoenvironmental evolution along the shallow water shelf in the South China Sea during the Miocene, the benthic foraminiferal assemblage and total organic carbon content(TOC) were analyzed at Hole LF14 located in the Lufeng Sag, northern South China Sea. Three benthic foraminiferal assemblages(e.g., the Uvigerina spp. assemblage, the Cibicides spp. assemblage, and the Cibicidoides spp. assemblage), corresponding to different watermass conditions, were recognized based on Q–mode factor analysis. Early studies suggested that Hole LF14 was deposited under semienclosed bay, middle to outer shelf or even upper bathyal environment during ～18.7–4.53 Ma. The dominant Uvigerina spp. assemblage was characterized by low diversity and shallow infaunal to infaunal species, indicating a warm, low–oxygenation and eutrophic conditions since the Early Miocene to MMCO(～18.7–14.24 Ma). An abrupt sea level drop and significant faunal changes were recorded during 14.24–13.41 Ma, suggesting development of the East Antarctic Ice Sheets, which resulted in a drop of sea level and change in benthic foraminiferal assemblages along the shallow water shelf. Beyond the Uvigerina spp.assemblage, the Cibicides spp. assemblage became important during the middle–late Middle Miocene(14.24–11.54 Ma). This assemblage was dominated by epifaunal species with relative high diversity, suggesting high–energy, high–oxygenation and oligotrophic conditions with episodic supply of organic food. The dominant Cibicidoides spp. assemblage with high diversity, indicates a mesotrophic conditions with relative high–oxygen content during the Late Miocene to Pliocene(11.54–4.53 Ma). The appearance and continuous occurrence of Ammonia spp. and Pseudorotalia spp. since 10.02 Ma, may reflect the influence of the Kuroshio Current.

Catch organism assemblages along artificial reefs area and adjacent waters in Haizhou Bay

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.

Cell Size Dependent Responses of Phytoplankton Assemblages to Nitrate and Phosphate Additions in Surface Waters of the Northern South China Sea

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 (

Early Cenozoic paleontological assemblages and provenance evolution of the Lishui Sag,East China Sea

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.

Modern pollen assemblages and their relationships with vegetation and climate on the northern slopes of the Tianshan Mountains, Xinjiang, China

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.

Mapping species assemblages of tropical forests at different hierarchical levels based on multivariate regression trees

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.

Fish assemblages in seagrass habitat along the Jordanian coast of the Gulf of Aqaba

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.

Modern pollen assemblages of the forest communities and their relationships with vegetation and climate in northern China

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).

Effects of Aquatic Vegetation on Fish Assemblages in a Freshwater River of Taihu Lake Basin, East China

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.

吉林榆树榆-302孔阿尔布期孢粉组合——兼论松辽盆地登楼库组的地质时代

榆302孔位于松辽盆地东部边缘,钻深899.30 m, 顶部3.15 m为第四系,上部683,65 m以砂岩为主,夹少量泥岩,下部212.50 m以灰色泥岩为主,夹砂岩及少量凝灰岩。以盆地内岩石地层比较,其上部应属登楼库组3段,下部为登楼库组2段,剖面缺失登楼库组4段,未钻及登楼库组1 段。整个剖面上的孢粉组合面貌基本一致,共有苔藓、蕨类植物孢子40属70余种、裸子植物花粉19属28种、被子植物花粉2属3种、藻类及疑源类6属8种。组合中的绝大部分属种都是我国北方早白垩世孢粉植物群的常见分子,如Cicatricosisporites(约占组合的7%—35%),Appendicisporites, Impardecispora, Pilosisporites, Aequitriradites, Kuylisporites, Triporoletes等。特别有意义的是自登楼库组2段开始即已出现大孢子Balmeisporites holodictyus,被子植物花粉Polyporites debi lis, Retitricolpites sp. 和沟鞭藻Vesperopsis zhaodongensis。登楼库组3 段出现曾见于阿尔布期的Scopusporislautus 及晚白垩世的Scopusporis verrucosus, Trochicola scollardiana, Verrucosisporites fuyuensis 等,证明其时代属早—中阿尔布期。榆302孔的孢粉证据表明登楼库组至少自登楼库组2 段起已进入阿尔布期,至于登楼库组1段因无更多新的资料佐证,阿普特期的时代定位?

阿尔金淡水泉早古生代泥质高压麻粒岩及其P-T演化轨迹

南阿尔金构造带淡水泉一带出露的含石榴石蓝晶石黑云母片麻岩是一套典型的泥质高压麻粒岩,其峰期特征矿物组合为石榴子石+蓝晶石+钾长石+金红石+石英。根据矿物内部一致性热力学数据和Thermocalc 3.23程序计算,确定其峰期变质温压条件为T>850℃和P>11kbar。结合岩相学研究和P-T视剖面图计算,可识别出该岩石经历了4个阶段的变质演化,构成了一个早期快速等温降压,后期近等压降温的顺时针型的退变质P-T演化轨迹,为与陆壳俯冲碰撞有关的高压变质事件的产物。该岩石锆石阴极发光图像显示其内部具有明显的核-边结构,核部为残留的原岩碎屑锆石,边部则表现为面状或扇状生长的变质锆石的特征。微区原位LA-ICP-Ms微量元素分析表明,核部测点的重稀土含量较高,对应Th/U接近于0.4,具有岩浆锆石的特征;边部测点的重稀土相对亏损,重稀土配分曲线平坦,对应Th/U比值均小于0.1,显示与石榴子石平衡共生的变质锆石特征。LA-ICP-MS微区定年获得其变质年龄为486±5Ma,该年龄值与阿尔金江尕勒萨依和英格利萨依两地超高压变质岩石的变质年龄相近,进一步证明沿阿尔金构造带南缘断续存在一条早古生代的高压-超高压变质岩带。另外,本次研究在获得该泥质高压麻粒岩峰期变质时代的同时,还获得该岩石原岩的形成时代上限值约为719Ma,从而限定阿尔金构造带南缘阿尔金群的形成时代可能不属古元古代,而应属新元古代。

扬子地台西南缘高家村岩体成因:岩石学、地球化学和年代学证据

高家村岩体辉长岩-橄榄岩中矿物组合、矿物结晶顺序及岩浆成因角闪石的普遍出现,指示矿物结晶于富含水的岩浆体系。主量元素Al_2O_3、CaO与MgO呈明显的负相关关系,表明斜长石并非早期堆晶相。稀土元素含量为5.97×10^(-6)～221.32×10^(-6),轻稀土元素相对富集,弱-中等程度轻重稀土元素分异,辉长岩-含辉石闪长岩无明显的Eu异常,而橄榄辉长岩-橄榄岩具有较明显的正Eu异常。微量元素中,辉长岩-含辉石闪长岩类具有明显的Nb、Ta、Zr、Hf和Ti负异常,Ba、Sr正异常,同时ε_(Nd)(t)为0.59～1.86,低于同期的亏损地幔值,与岛弧基性岩浆特征类似。含辉石闪长岩SHRIMP锆石U-Pb年龄结果822±8Ma,为新元古代。综合分析认为,高家村岩体应形成于受俯冲带流体改造的亏损上地幔部分熔融。

Cretaceous Phytoplankton Assemblages from Songke Core-1(SK-1,N & S) of Songliao Basin,NE China

The Songliao Basin,the biggest Cretaceous oil-gas producing lacustrine basin in northeast China, contains the giant Daqing Oilfield situated in the central part.Lacustrine setting dominated the basin during the Cretaceous period.The SK-I drilling, located in the northern central part of the Songliao Basin,was completed in 2007 and is supposed to be a possible breakthrough in lake investigation.This paper aims to study the Cretaceous

Sporopollen Assemblages from the Cretaceous Yimin Formation of the Hailar Basin,Inner Mongolia,China

Three sporopollen assemblages are recognized for the first time from the Cretaceous Yimin Formation in the Hailar Basin of eastern Inner Mongolia. They are （in ascending order）： the lmpardecispora-Aequitriradites- Clawttipollenites assemblage; the Triporoletes-Pilosisporites-Asteropollis assemblage; and the Appendicisporites- Asteropollis-Tricolpites assemblage, distributed in Members 1, 2 and 3 of the Yimin Formation respectively. Recognition of this biostratigraphic sequence is very important for the division and correlation of the Yimin Formation in the basin. Meanwhile, the age of the Yimin Formation is considered to be Barremian to Early Albian based on the palynological data.

Early Cretaceous Palynological Assemblages of the Shuangliao Fault Depression, Songliao Basin and their Geological Implications

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.

Effects of shrub presence and shrub species on ground beetle assemblages (Carabidae,Curculionidae and Tenebrionidae) in a sandy desert,northwestern China

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.

A Comparative Study of Fish Assemblages Near Aquaculture, Artificial and Natural Habitats

Habitat plays a critical role in regulating fish community structure. Using the data collected from a monthly trammel net survey in Ma'an archipelago off the east coast of China, we evaluated impacts of five different habitats(artificial reefs, mussel farms, cage aquaculture, rocky reefs and soft bottom) on fish assemblages. This study suggests that artificial reefs(AR) have significantly higher species richness, abundance and diversity than mussel farms(MF) or soft bottom(SB) habitats during most seasons, and that fish taxa in the AR habitats are similar to those in the rocky reef(RR) habitats. Two different fish assemblage patterns were revealed in the study area using non-metric multidimensional scaling ordination: an assemblage dominated by reef fishes(especially by Scorpaenidae species) in AR, RR and cage aquaculture(CA) habitats and an assemblage dominated by Sciaenidae species in MF and SB habitats. We suggest that reef fishes play a key role in differentiating fish community structures in the study area. Although few differences in fish abundance and diversity were found between the CA and SB habitats, a more diverse age structure was observed in the CA habitats. A much more complex fish assemblage and enhanced population of local species were established as a result of the presence of both floating and fixed artificial structures, probably through improved survival rates.

北方草原区主要群落类型表土花粉分析

建立花粉与现代植被的关系是利用地层沉积物中的花粉记录恢复古植被、古气候研究的基础工作之一。中国北方草原区39个表土花粉研究表明,蒿属、藜科是草原区花粉组合的主要成分,以禾本科为建群种的草原群落花粉组合以蒿属花粉为主,禾本科花粉多低于10%。禾本科花粉的低代表性可能与其分蘖繁殖、花粉产量低有关。草原区表土花粉浓度与植被盖度相关不明显。典型草原与荒漠草原花粉组合存在着明显的区别,典型草原区藜科花粉百分比一般低于25%,荒漠草原区一般高于25%。DCA分析表明,草原区针叶树、莎草科、石竹科花粉代表较湿润的环境,蒿、藜科、锦鸡儿、柽柳、白刺花粉代表较干燥的环境,阔叶树、禾本科、菊科、毛茛科、蓼科、豆科、唇形科(百里香)、虎榛子+榛、蔷薇科花粉代表的环境介于前两组之间。DCA分析用于草原区花粉组合研究具有较好的环境指示意义。