Characterization of bacterial communities associating with larval development of Yesso Scallop (<Emphasis Type="Italic">Patinopecten yessoensisis</Emphasis> Jay, 1857) by high-throughput sequencing

Bacterial community presumably plays an essential role in inhibiting pathogen colonization and maintaining the health of scallop larvae, but limiting data are available for Yesso scallop (Patinopecten yessoensisis Jay, 1857) larval development stages. The aim of this study was to characterize and compare the bacterial communities associating with Yesso scallop larval development at fertilized egg S1, trochophora S2, D-shaped larvae S3, umbo larvae S4, and juvenile scallop S5 stages by Illumina high-throughput sequencing. Genomic DNA was extracted from the larvae and their associating bactera, and a gene segment covering V3-V4 region of 16S rRNA gene was amplified and sequenced using an Illumina Miseq sequencer. Overall, 106760 qualified sequences with an average length of 449 bp were obtained. Sequences were compared with those retrieved from 16S rRNA gene databases, and 4 phyla, 7 classes, 15 orders, 21 families, 31 genera were identified. Proteobacteria was predominant phylum, accounting for more than 99%, at all 5 larval development stages. At genus level, Pseudomonas was dominant at stages S1 (80.60%), S2 (87.77%) and S5 (68.71%), followed by Photobacterium (17.06%) and Aeromonas (1.64%) at stage S1, Serratia (6.94%), Stenotrophomonas (3.08%) and Acinetobacter (1.2%) at stage S2, Shewanella (25.95%) and Pseudoalteromonas (4.57%) at stage S5. Moreover, genus Pseudoalteromonas became dominant at stages S3 (44.85%) and S4 (56.02%), followed by Photobacterium (29.82%), Pseudomonas (11.86%), Aliivibrio (8.60%) and Shewanella (3.39%) at stage S3, Pseudomonas (18.16%), Aliivibrio (14.29%), Shewanella (4.11%), Psychromonas (4.04%) and Psychrobacter (1.81%) at stage S4. From the results, we concluded that the bacterial community changed significantly at different development stages of Yesso Scallop larvae.     

Characterization and in-vivo evaluation of potential probiotics of the bacterial flora within the water column of a healthy shrimp larviculture system

A thorough understanding of the normal bacterial flora associated with shrimp larviculture systems contributes to probiotic screening and disease control.The bacterial community of the water column over a commercial Litopenaeus vannamei larval rearing run was characterized with both culture-dependent and culture-independent methods.A total of 27 phylotypes at the species level were isolated and identified based on 16 S rDNA sequence analysis.Denaturing gradient gel electrophoresis(DGGE) analysis of the V3–V5 region of 16 S rRNA genes showed a dynamic bacterial community with major changes occurred from stages zoea to mysis during the rearing run.The sequences retrieved were affiliated to four phyla,Proteobacteria,Actinobacteria,Bacteroidetes,and Firmicutes,with the family Rhodobacteraceae being the most frequently recovered one.Subsequently,13 representative strains conferred higher larval survival than the control when evaluated in the in-vivo experiments;in particular,three candidates,assigned to Phaeobacter sp.,Arthrobacter sp.,and Microbacterium sp.,significantly improved larval survival( P 0.05).Therefore,the healthy shrimp larviculture system harbored a diverse and favorable bacterial flora,which contribute to larval development and are of great importance in exploiting novel probiotics.     

Molecular characterization of sulfate-reducing bacteria community in surface sediments from the adjacent area of Changjiang Estuary

Sulfate-reducing bacteria (SRB), which obtain energy from dissimilatory sulfate reduction, play a vital role in the carbon and sulfur cycles. The dissimilatory sulfite reductase (Dsr), catalyzing the last step in the sulfate reduction pathway, has been found in all known SRB that have been tested so far. In this study, the diversity of SRB was investigated in the surface sediments from the adjacent area of Changjiang Estuary by PCR amplification, cloning and sequencing of the dissimilatory sulfite reductase beta subunit gene (dsrB). Based on dsrB clone libraries constructed in this study, diversified SRB were found, represented by 173 unique OTUs. Certain cloned sequences were associated with Desulfobacteraceae, Desulfobulbaceae, and a large fraction (60%) of novel sequences that have deeply branched groups in the dsrB tree, indicating that novel SRB inhabit the surface sediments. In addition, correlations of the SRB assemblages with environmental factors were analyzed by the linear model-based redundancy analysis (RDA). The result revealed that temperature, salinity and the content of TOC were most closely correlated with the SRB communities. More information on SRB community was obtained by applying the utility of UniFrac to published dsrB gene sequences from this study and other 9 different kinds of marine environments. The results demonstrated that there were highly similar SRB genotypes in the marine and estuarine sediments, and that geographic positions and environmental factors influenced the SRB community distribution.     

Species-area relationship within and across functional groups at alpine grasslands on the northern Tibetan Plateau,China

The species-area relationship(SAR) is one of the most fundamental concepts in community ecology and is helpful for biodiversity conservation.However,few studies have systematically addressed this topic for different alpine grassland types on the Tibetan Plateau,China.We explored whether the plant composition of different functional groups affects the manner in which species richness increases with increasing area at scales ≤ 1.0 m~2.We also compared species richness(S) within and across forbs,legumes,sedges and grasses,with sampling subplot area(A) increasing from 0.0625 m~2 to 1.0 m~2 between alpine meadow and steppe communities.We applied a logarithmic function(S = b_0 + b_1 ln A) to determine the slope and intercept of SAR curves within and across functional groups.The results showed that the logarithmic relationship holds true between species richness and sampling area at these small scales.Both the intercept and slope of the logarithmic forbs-area curves are significantly higher than those for the three other functional groups(P 0.05).Forb accounts for about 91.9 % of the variation in the intercept and 75.0% of the variation in the slope of the SAR curve when allfunctional groups' data were pooled together.Our results indicated that the different SAR patterns should be linked with species dispersal capabilities,environmental filtering,and life form composition within alpine grassland communities.Further studies on the relationship between species diversity and ecosystem functions should specify the differential responses of different functional groups to variations in climate and anthropogenic disturbances.     

Collecting <Emphasis Type="Italic">Ophiocordyceps sinensis</Emphasis>: an emerging livelihood strategy in the Garhwal,Indian Himalaya

In the Garhwal of Uttarakhand, India, the Bhotiya, an ethnically and culturally distinct tribal group, were historically engaged in seasonal migration (i.e. transhumance) to take advantage of scarce mountain resources and trade relations with Tibet. This livelihood practice has all but disappeared. Households are adapting to these changing circumstances by engaging in the collection and sale of the valuable alpine medicinal fungus Ophiocordyceps sinensis, widely known as Cordyceps. The collection of this fungus has exploded, emerging as a lucrative yet high-risk livelihood strategy for many Bhotiya communities. The Bhotiyas’ historic herding and trade-based interactions and knowledge of these alpine environments where Cordyceps are found uniquely positions them to access this valuable biological resource. Elsewhere in the Himalayan region, some households are earning as much as two-thirds of their income from the collection of Cordyceps; in China Cordyceps is now listed as an endangered species due to intense over-exploitation in the Tibetan Plateau. This paper seeks to fill the void in the scientific literature on the social, ecological and economic aspects of the emerging Cordyceps trade in the Garhwal. Our study investigates the socio-spatial dimensions of Cordyceps collection in the high alpine meadows. We document how a fusion of local knowledge and practice with alpine mountain systems has served to reinvigorate the economic integrity of mountain communities at a time of rapid socio-economic change and to reimagine a new relationship between alpine resources and community well-being. The article offers suggestions to address the sustainability of both Cordyceps collection and livelihood activities which hinge on this fungus population. We find a need for (1) community-based conservation measures that are rooted in (2) secure resource access rights for local communities to continue sustainable collection and sale of Cordyceps and (3) participatory-and science-based processes for determining appropriate local collection numbers.     

Spatial and seasonal pattern of macrozoobenthic assemblages and the congruence in water quality bioassessment using different taxa in artificial Mingzhu Lake in Shanghai

The spatial and seasonal pattern of macrozoobenthic structure and its relationship with environmental factors were studied from July 2006 to April 2008 in Mingzhu Lake, Chongming Island, Shanghai at the Changjiang River mouth. The congruences in water quality bioassessment based on diversity and biotic indices and using different taxonomic categories were also explored to find the best assessment method of water quality for the lake. All major structural characteristics of macrozoobenthic community, including species composition, abundance, biomass and four biomass-based diversity indices (Shannon’s diversity, Simpson’s diversity, Pielou’s evenness and Simpson’s evenness index) fluctuated significantly in season but in space. The above four abundance-based diversity indices plus abundance-based Margalef’s richness index did not display significant spatial variations; and significant seasonal differences were found in three indices only. Water temperature was the key environmental factor responsible for macrozoobenthic spatio-temporal distribution patterns. Water quality assessed by Shannon’s index (H _a′) and biological pollution index (BPI) rather than the other four biotic indices were consistent with those by trophic state index (TSI). Results from chironomids and oligochaetes did not always agree to those from the whole community when H _a′ or Hilsenhoff biotic index was applied to bioassessment. Therefore, combining multiple indices and avoiding a single taxonomic category to assess water quality are strongly recommended and in Mingzhu Lake using a mixture of H _a′ and BPI will ensure the most effective investigation of water quality. Our results also show that the main structural characteristics of macrozoobenthic communities in the small lake may display consistent spatial patterns.     

Succession and seasonal variation in epilithic biofilms on artificial reefs in culture waters of the sea cucumber <Emphasis Type="Italic">Apostichopus japonicus</Emphasis>

Periphytic biofilms in aquaculture waters are thought to improve water quality, provide an additional food source, and improve the survival and growth of some reared animals. In the Asia- Pacific region, particularly in China, artificial reefs are commonly used in the commercial farming of sea cucumbers. However, few studies have examined the epilithic biofilms on the artificial reefs. To gain a better understanding of the succession of epilithic biofilms and their ecological processes in sea cucumber culture waters, two experiments were conducted in culture waters of the sea cucumber Apostichopus japonicus in Rongcheng, China, using artificial test panels. On the test panels of succession experiment, more than 67 species were identified in the biofilms. On the test panels of seasonal variation experiment, more than 46 species were recorded in the biofilms. In both experiments, communities of epilithic biofilms were dominated by diatoms, green algae and the annelid Spirorbis sp. In the initial colonization, the dominant diatoms were Cocconeis sp., Amphora spp. and Nitzschia closterium in June, which were succeeded by species of Navicula, Cocconeis and Nitzschia (July to September), and then by Licmophora abbreviata, Nitzschia closterium and Synedra spp. in the following months. A diatom bloom in the autumn and filamentous green algae burst in the summer were also observed. Ecological indices well annotated the succession and seasonal changes in epilithic communities. Multidimensional scaling (MDS) analysis found significant differences in diatom community composition among months and seasons. Fast growth of biofilms was observed in the summer and autumn, whereas the biomass of summer biofilms was largely made up of filamentous green algae. Present results show that the components of epilithic biofilms are mostly optimal foods of A. japonicus, suggesting that biofilms on artificial reefs may contribute important nutritional sources for sea cucumbers during their growth seasons. Future works should include quantitative determination of the contribution of epilithic biofilms to the diet of A. japonicus, potential roles of epilithic biofilms in regulating the water quality of sea cucumber ponds, and the regulation of epilithic biofilms in sea cucumber culture ponds.     

Effects of vegetation coverage and seasonal change on soil microbial biomass and community structure in the dry-hot valley region

Soil microorganisms are sensitive indicator of soil health and quality. Understanding the effects of vegetation biomass and seasonal change on soil microorganisms is vital to evaluate the soil quality and implement vegetation restoration. This study analyzed the soil phospholipid fatty acids (PLFAs) in fresh and withered Kudzu (Pueraria montana var. lobata) vegetation conditions in different seasons. The results showed that vegetation biomass and seasonal change significantly affected microbial biomass and its community structure. Both fresh and withered Kudzu cover significantly increased soil microbial biomass, and the growth effect of microbes in the soil with fresh Kudzu cover was more obvious than that with withered Kudzu cover. Compared with the dry season, the rainy season significantly increased the microbial biomass and the B/F (the ratio of bacterial to fungal PLFAs) ratio but dramatically reduced the G+/G- (the ratio of gram-positive to gram-negative bacteria PLFAs). Kudzu cover and seasonal change had a significant effect on microbial structure in soil covered by higher vegetation biomass. Furthermore, soil temperature and moisture had different correlations with specific microbial biomass in the two seasons. Our findings highlight the effect of Kudzu vine cover on the soil microenvironment and soil microhabitat, enhancing the soil quality in the Dry-hot Valley of Jinsha River, Southwest China.     

Spatiotemporal variation in community structure of marine benthic ciliates in the Yellow Sea during and after macroalgal and giant jellyfish blooms

The annual bloom of the green macroalgal Ulva prolifera from May through July since 2008 and another of giant jellyfish Nemopilema nomurai from June through September have been frequent events in the Yellow Sea. However, the patterns of benthic ciliate communities during and after the blooms are still not known. In combination with analyses of benthic environmental factors, we investigated the distribution and community composition of benthic ciliates in the Yellow Sea in July and November 2011. In July, ciliates had high standing crops and diversity in the northern Yellow Sea, and in the inshore area off the southern Shandong Peninsula, where large numbers of green macroalgae accumulated. In November, the abundance, biomass and diversity of ciliates were high in the sea areas off the Shandong Peninsula and Changjiang estuary, where a large quantity of jellyfish occurred in August. Neither the abundance nor the biomass had significant difference between seasons, or between different compartments of the Yellow Sea. The species number, and both Margalef and Shannon-Wiener indices of ciliates were all significantly higher in November than in July. In both seasons, prostomateans and karyorelicteans consistently constituted the first and second most important ciliate groups in biomass; and carnivorous ciliates constituted the primary feeding type in terms of biomass as well as species richness, followed by bacterivores, algivores and omnivores. Compared with that in June 2007 when no macroalgae occurred, the percentage of small-sized bacterivores (e.g. Metacystis spp., Euplotes spp. and scuticociliates) increased in July 2011. The proportion of carnivorous ciliates increased in November, and this increased dominance of carnivorous ciliates may be a response to the increase in predominance of heterotrophic nanoflagellates, which might in turn be ascribed to an effect of green macroalgal and giant jellyfish blooms in the Yellow Sea.     

Variations in leaf functional traits and physiological characteristics of <Emphasis Type="Italic">Abies georgei</Emphasis> var. <Emphasis Type="Italic">smithii</Emphasis> along the altitude gradient in the Southeastern Tibetan Plateau

Variations in leaf functional traits of Abies georgei var. smithii at 3700, 3900, 4100, 4300, and 4390 m altitude were investigated in 15 typical plots in the Southeastern Tibetan Plateau. In each plot, three seedlings were selected, of which functional leaves in current-year sunny branches were chosen for the measurement of morphological, photosynthetic, and physiological and biochemical characteristics, and their variations were analyzed. Results showed that significant variations existed among the leaf functional traits of A. georgei var. smithii along the altitudinal gradient, as well as their physiological adaption indicators. Leaf area decreased, while the mass per area and thickness of leaf increased at an altitude above 4,100 m. The maxima of pigment, total nitrogen concentration, net photosynthesis rate during light-saturated, and when water use efficiency appeared at 4100 m altitude. In addition, A. georgei var. smithii seedlings regulated the activities of superoxide dismutase and ascorbate peroxidase to resist abiotic stress under 4100 m altitude. Meanwhile, malondialdehyde concentration and the dark respiration rate rapidly increased, which indicates that A. georgei var. smithii seedlings suffered from heavy abiotic stress from 4100 m to 4390 m altitude. Basing on variations in leaf functional traits along the altitude gradient, we inferred that 4100 m altitude was the suitable region for A. georgei var. smithii growth in the Sygera Mountain. Moreover, the harsh environment was the main limiting factor for A. georgei var. smithii population expansion to high altitude.     

Genotype and Phylogenetic Diversity of <Emphasis Type="Italic">Symbiodinium</Emphasis> ITS2 Sequences Within Clade C in Three Typical Coral Species from Luhuitou Fringing Reef of the South China Sea

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

The influence of environmental variables on distribution patterns of Irano-Turanian forests in Alborz Mountains,Iran

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

Effects of wetland vegetation on soil microbial composition: A case study in Tumen River Basin,Northeast China

Hydrology plays a dominant role in wetland plant distribution and microbial composition, but few studies explicitly attempted to relate the linkage between wetland vegetation and microbial community. The present study consisted of five wetland plant communities along three adjacent flood gradients zones (zone 1 dominated by Carex appendiculat, zone 2 dominated by Eleocharis ovate, and zone 3 dominated by Phragmites australis/Bidens pilosa/Calamagrostis angustifolia, which formed separate, monoculture patches). Gram negative and arbuscular mycorrhizal fungal phospholipid fatty acid (PLFA) are more abundant in the site with short flooding period (zone 3) than in the site with long flooding period (zone 1), and they are also different in the P. australis, B. spilosa and C. angustifolia of zone 3. Principle Component Analysis (PCA) showed that the flooding period could explain 92.4% of variance in microbial composition. Redundancy Analysis (RDA) showed that available nitrogen (AN), total nitrogen (TN) and soil organic matter (SOM) could explain the 79.5% of variance in microbial composition among E. ovata, P. australis, B. pilosa and C. angustifolia. Results demonstrated that flooding period was the main factor in driving the microbial composition and plant-derived resources could influence soil microbial composition in the seasonally flooded zones.     

Morphologies of eumelanins from the ink of six cephalopods species measured by atomic force microscopy

The morphologies of eumelanin, isolated from the six cephalopods species Sepia esculenta, Sepia lycidas, Sepia pharaonis, Sepiella japonica, Euprymna berryi, and Uroteuthis (Photololigo) edulis, were investigated using atomic force microscopy (AFM). The results showed that the hierarchical aggregate structures of irregular spherical particles with different diameters are the common characteristics of these eumelanins. Furthermore, the diameters of these spherical particles present an uneven distribution in a wide range and mainly concentrate in the range of about 20-150 nm. In addition, the eumelanin from different cephalopods species show obvious differences in the morphologies, which is illustrated by different assembly forms of diverse aggregate units and the quantitative features of eumelanin particles derived from the images.     

Impact of <Emphasis Type="Italic">Vibrio parahaemolyticus</Emphasis> and white spot syndrome virus (WSSV) co-infection on survival of penaeid shrimp <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

White spot syndrome virus (WSSV) is an important viral pathogen that infects farmed penaeid shrimp, and the threat of Vibrio parahaemolyticus infection to shrimp farming has become increasingly severe. Viral and bacterial cross or superimposed infections may induce higher shrimp mortality. We used a feeding method to infect Litopenaeus vannamei with WSSV and then injected a low dose of V. parahaemolyticus (WSSV+Vp), or we first infected L. vannamei with a low-dose injection of V. parahaemolyticus and then fed the shrimp WSSV to achieve viral infection (Vp+WSSV). The eff ect of V. parahaemolyticus and WSSV co-infection on survival of L. vannamei was evaluated by comparing cumulative mortality rates between experimental and control groups. We also spread L. vannamei hemolymph on thiosulfate citrate bile salt sucrose agar plates to determine the number of Vibrio, and the WSSV copy number in L. vannamei gills was determined using an absolute quantitative polymerase chain reaction (PCR) method. LvMyD88 and Lvakt gene expression levels were detected in gills of L. vannamei by real-time PCR to determine the cause of the diff erent mortality rates. Our results show that (1) the cumulative mortality rate of L. vannamei in the WSSV+Vp group reached 100% on day 10 after WSSV infection, whereas the cumulative mortality rate of L. vannamei in the Vp+WSSV group and the WSSV-alone control group approached 100% on days 11 and 13 of infection; (2) the number of Vibrio in the L. vannamei group infected with V. parahaemolyticus alone declined gradually, whereas the other groups showed significant increases in the numbers of Vibrio (P<0.05); (3) the WSSV copy numbers in the gills of the WSSV+Vp, Vp+WSSV, and the WSSV-alone groups increased from 10⁵ to 10⁷ /mg tissue 72, 96, and 144 h after infection, respectively. These results suggest that V. parahaemolyticus infection accelerated proliferation of WSSV in L. vannamei and vice versa. The combined accelerated proliferation of both V. parahaemolyticus and WSSV led to massive death of L. vannamei.     

Spatial patterns and storage composition of woody debris in a natural secondary forest dominated by <Emphasis Type="Italic">Pinus tabulaeformis</Emphasis> on Loess Plateau,China

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

Positive adaptation of <Emphasis Type="Italic">Salix eriostachya</Emphasis> to warming in the treeline ecotone,East Tibetan Plateau

Understanding of treeline ecotone ecophysiological adaptation to climate warming is still very limited. Furthermore, it is difficult to predict which plant species could dominate in the future. For this reason, a study was conducted in the treeline ecotone, East Tibetan Plateau to detcct the adaptation of the dwarf willow (Salix eriostachya) to experimental warming. Compared to ambient conditions, the experimental warming advanced the bud break by 12 days, delayed the leaf abscission by 20 days, and prolonged the growing period by 28 days. It also increased photosynthesis (47%), number of leaves (333%), leaf area (310%), and carbon sequestration of the dwarf willow. Experimental warming did not affect carbon use efficiency, but decreased water use efficiency significantly. Experimental warming enhanced the clonal ramets of Salix eriostachya (+ 3.7 shrubs m^-2). The frequent air temperature fluctuations had minor effect on Salix eriostachya. Based on these findings, we highlighted that Salix eriostachya could dominate in the community treeline ecotone of east Tibetan Plateau in the future climate warming scenario.     

Effects of different phosphorus concentrations and N/P ratios on the growth and photosynthetic characteristics of <Emphasis Type="Italic">Skeletonema costatum</Emphasis> and <Emphasis Type="Italic">Prorocentrum donghaiense</Emphasis>

The effects of different phosphorus (P) concentrations (0.36, 3.6, and 36 μmol/L corresponding to low-, middle-, and high-P concentration groups, respectively) and nitrogen (N)/P ratios on the growth and photosynthetic characteristics of Skeletonema costatum and Prorocentrum donghaiense were studied. For both species, the high-P (HP) concentration group showed the greatest algal density and highest specific growth rate. Changes in the maximum efficiency of photosystem II (F _v /F _m ) were monitored under the various P and N/P conditions. The largest decrease in F _v /F _m was in the low-P (LP) group in S. costatum and in the HP group in P. donghaiense. There were high rapid light curves and photochemical quantum yields (Φ _PSII) for S. costatum in the HP group, while the actual photosynthetic capacity was higher in P. donghaiense than in S. costatum in the MP group. Under eutrophic but relatively P-restricted conditions, P. donghaiense had higher photosynthetic activity and potential, which could cause this dinoflagellate to increasingly dominate the phytoplankton community in these conditions. Under the same P concentration and N/P ratio, P. donghaiense had a larger relative maximum rate of electron transport and higher Φ _{PS II} values than those of S. costatum. These differences between P. donghaiense and S. costatum may explain the interaction and succession patterns of these two species in the Changjiang (Yangtze) River estuary from a photosynthesis perspective.     

Responses of soil inhabiting nitrogen-cycling microbial communities to wetland degradation on the Zoige Plateau,China

The wetlands on the Zoige Plateau have experienced serious degradation, with most of the original marsh being converted to marsh meadow or meadow. Based on the 3 wetland degradation stages, we determined the effects of wetland degradation on the structure and relative abundance of nitrogen-cycling (nitrogen-fixing, ammonia-oxidizing, and denitrifying) microbial communities in 3 soil types (intact wetland: marsh soil; early degrading wetland: marsh meadow soil; and degraded wetland: meadow soil) using 454-pyrosequencing. The structure and relative abundance of nitrogen-cycling microbial communities differed in the 3 soil types. Proteobacteria was the predominant phylum in most soil samples but the most abundant soil nitrogen-fixing and denitrifying microbial bacteria differed at the class, order, family, and genus levels among the 3 soil types. At the genus level, the majority of nitrogen-fixing bacterium sequences related to Bradyrhizobium were from marsh and marsh meadow soils; whereas those related to Geobacter originated from meadow soil. The majority of ammonia-oxidizing bacterium sequences related to Nitrosospira were from marsh (except for the 40-60 cm layer), marsh meadow and meadow soils; whereas those related to Candidatus Solibacter originated from 40-60 cm layer of marsh soil. The majority of denitrifying bacterium sequences related to Candidatus Solibacter and Anaeromyxobacter were from marsh and meadow soils; whereas those related to Herbaspirillum originated from meadow soil. The distribution of operational taxonomic units (OTUs) and species were correlated with soil type based upon Venn and Principal Coordinates Analysis (PCoA). Changes in soil type, caused by different water regimes were the most important factors influencing compositional changes in the nitrogen-fixing, ammonia-oxidizing, and denitrifying microbial communities.     

Experimental study on large wood filtration performance by herringbone water-sediment separation structure

A herringbone water-sediment separation structure(hereinafter referred to as "herringbone structure") has been shown to be effective in separating coarse inorganic debris; however, less is known regarding the large wood(LW) filtration effect in this structure. This paper presents preliminary research on the wood filtration effect of the herringbone structure based on physical model tests.The results show that the herringbone structure exhibited effective performance in large wood size segregation, with a 100% component filtration rate for LW that diameter(D) larger than ribbed beam opening width(a). The total filtration rate also exceeded 80% when the Fraud number(Fr) is larger than 2.64 and increased with the increase of Fr. After exceeding Frmax, total filtration rate would be decreased due to overflow. Beside flow condition,structure parameters influence significantly on LW filtration rate. We attempt to explain the filtration process via particle contact trajectory and particle movement trajectory. The inclined angle of ribbed beam(γ) contributed the most variation to the filtration rate via influencing the coincidence with particle contact trajectory and particle movement trajectory. The high sensitivity coefficient of ribbed beam(θ) under relatively low Fr conditions implies remarkable influences on LW filtration effects by causing clogging problem. The ribbed beam opening width(a) together with LW diameter(D) influenced the size segregation performance.