Jingpo Lake Research Articles

Metagenomic Analysis Reveals the Response of Microbial Communities and Their Functions in Lake Sediment to Environmental Factors

Jingpo Lake is the largest mountain barrier lake in China and plays a key role in breeding, power generation, and providing a source of drinking water. Microbes are important participants in the formation of lake resources and energy cycles. However, the ecological protection of Jingpo Lake has faced serious challenges in recent years. In this study, we investigate the responses of the microbial community's composition of sediments at five locations to an environmental gradient representing water quality and water-depth changes using a metagenomic sequence. We found that the diversity and composition of the microbiota sediments were altered spatially and correlated with the physicochemical factors of water samples. In the microbial community, relatively lower Chao1, alternating conditional expectations, and Shannon and Simpson indices were found at the shallowest location with higher total phosphorus and chlorophyll a. Furthermore, the Kyoto Encyclopedia of Genes and Genomes analysis revealed that the metabolism function was the most abundant functional classification in Jingpo Lake. The levels of total phosphorus, chlorophyll a and pH were positively correlated with the abundance of Flavobacterium and the bacterial functions of the carbohydrate metabolism and amino acid metabolism. In conclusion, our results reveal the physical and chemical characteristics, as well as the microbial community characteristics, of Jingpo Lake, which provides new insights for studying the relationship between environmental factors and the bacterial community distribution of freshwater ecosystems, in addition to also providing a theoretical basis for the environmental monitoring and protection of the lake.

Application of Phytoplankton Taxonomic α-Diversity Indices to Assess Trophic States in Barrier Lake: A Case of Jingpo Lake

Phytoplankton taxonomic α-diversity indices are useful tools to characterize the trophic states in freshwater ecosystems. However, the application of these indices to assess trophic states in large barrier lakes is rare, especially in China. To test the usefulness of phytoplankton taxonomic α-diversity indices in trophic state assessments, we investigated the taxonomic α-diversity-Comprehensive Trophic Level Index (TLI) relationships in the second largest alpine lava barrier lake (Jingpo Lake, China) in the rainy and dry season from 2017 to 2018. Based on a two-year dataset, we found that there was a significant difference in the phytoplankton community, α-diversity indices, and TLI dynamic between the rainy season and the dry season. First, there was significant variation in phytoplankton abundance, the Margalef index, and the Shannon-Wiener index in different hydrological periods (p < 0.05). Second, the mean TLI in the rainy season (44 ± 5) was higher than in the dry season (41 ± 5) (p < 0.05). Lastly, the response characteristics of the Margalef and Shannon-Wiener index with TLI were different in different hydrological periods, and the relationship between the Pielou evenness index and TLI was weak. This study highlights that phytoplankton taxonomic α-diversity indices are relevant tools in water quality assessments but selecting the fit index is necessary. The current study provides key information about phytoplankton community, α-diversity, and trophic states in the largest alpine lava barrier lake, and the results of the study will benefit water quality management and biodiversity conservation in barrier lakes.

Flavor Differences of Edible Parts of Grass Carp between Jingpo Lake and Commercial Market.

This study investigated the flavor differences among three individual parts (abdomen, back, and tail) of Jingpo Lake grass carp (JPGC) and commercial grass carp (CGC). The growing environment and fish parts influenced the volatile compounds of the fish. The highest total contents of alcohols and ethers were found in the back of JPGC (p < 0.05). The combination of an electronic tongue and electronic nose (E-nose) could effectively distinguish the flavor differences between the different parts of JPGC and CGC by principal component analysis. Both the content of total free amino acids (FAAs) and content of amino acids contributing to the sweet and fresh flavors were higher in JPGC than CGC (p < 0.05). Among the ATP-associated products, the inosine 5’-monophosphate (IMP) contents of the back and tail of JPGC were higher (p < 0.05), but the abdomen content was lower (p > 0.05) than the respective contents in the corresponding parts of CGC. Sensory evaluation shows that JPGC had a better texture, odor, and taste, compared to CGC. Correlation analysis showed that the E-nose data and FAAs were highly correlated with the content of alcohols, aldehydes, and ethers. This study showed that the flavors of the different parts of JPGC differed significantly from those of CGC.

Developing Water-Quality Model for Jingpo Lake Based on EFDC

Water-quality model simulation is the key to understanding hydrological processes and water-quality dynamic(s). In this study, Jingpo Lake, which is the most typical lake in the northern cold region of China, was selected as the research object. A numerical simulation model for transporting and diffusing the chemical oxygen demand (CODMn) and ammonia nitrogen (NH3N) with ice-covered and open-water periods was constructed and calibrated using the Environmental Fluid Dynamics Code (EFDC). Parameters such as the bottom roughness, ice roughness, diffusion coefficient, horizontal momentum diffusivity, molecular eddy viscosity, molecular diffusivity, buoyancy influence coefficient, CODMn decay rate and NH3N decay rate were validated. The research findings show that there were differences in the hydrodynamic water-quality changing process during the ice-covered and open-water periods, as well as for the seasonal ice-covered waterbody. The key parameter decay rates of the CODMn and NH3N in the ice-covered periods were lower than those in the open-water periods due to the water-temperature decline. The R2 of the CODMn and NH3N reached 90.71% and 79.79%, respectively. Thus, it may be concluded that the EFDC model could well reflect changes in the water level of Jingpo Lake, as well as the transport and diffusion of the CODMn and NH3N in Jingpo Lake.

The characteristics of spatial-temporal distributions of fish resources in Lake Jingpo based on hydroacoustic assessment

2020年5、7和10月，采用多网目复合刺网调查和水声学探测相结合的方式对镜泊湖鱼类群落时空动态和资源量进行调查.渔获物调查共采集鱼类4目6科29种，其中鲤科鱼类最多，主要经济鱼类为鲢（Hypophthalmichthys molitrix）、鳙（Aristichthys nobilis）、蒙古鲌（Chanodichthys mongolicus）、瓦氏雅罗鱼（Leuciscus waleckii）、鲤（Cyprinus carpio）、翘嘴鲌（Culter alburnus）.蒙古鲌和（Hemiculter leucisculus）为优势种.水声学探测结果表明，镜泊湖鱼类密度在春季、夏季和秋季分别为836、7216和2724 ind./hm²，其中夏季鱼类密度最高且主要集中于中部和南部区域，春季和秋季鱼类密度则呈现从南至北递减的趋势.春、夏、秋季鱼类的平均目标强度为-43.4、-50.0和-46.5 dB，估算的平均全长分别为34.0、18.0和25.2 cm，推算的平均体重分别为272.7、43.7和135.2 g.结合各季节平均密度，估算出春、夏、秋季镜泊湖鱼类资源量分别为2052、2835和3313 t.镜泊湖鱼类密度与环境因子之间的冗余分析结果表明，水体总悬浮物、叶绿素a、水温和溶解氧是影响鱼类群落结构变化的关键环境因子.从水声学探测和刺网调查的结果来看，镜泊湖渔获物小型化问题突出，鱼类资源呈现衰退趋势，渔业资源的不合理利用是造成镜泊湖鱼类资源衰退的主要因素.因此建议强化对自然捕捞的管理，严格控制捕捞数量和规格，保障鱼类资源自然增殖，结合牡丹江流域污染防治、改善鱼类栖息地环境等鱼类生境修复措施，以促进鱼类资源的恢复.;In May, July and October 2020, a combination of multi-mesh gillnet and hydroacoustic survey was undertaken to investigate the characteristics of spatial-temporal distributions of fish resources of Lake Jingpo. A total of 29 fish species, belonging to four orders and six families, were collected during the survey. The main economic fish are Hypophthalmichthys molitrix, Aristichthys nobilis, Chanodichthys mongolicus, Leuciscus waleckii, Cyprinus carpio, and Culter alburnus. The dominant species are Chanodichthys mongolicus and Hemiculter leucisculus. The average fish density was 836 ind./hm² in spring, 7216 ind./hm² in summer and 2724 ind./hm² in autumn. In summer, fish mainly inhabited in the central and southern regions. In spring and autumn, the species density showed a decreasing trend from the south to the north. The average target strengths were -43.4, -50.0 and -46.5 dB in spring, summer and autumn, the estimated average total lengths 34.0, 18.0 and 25.2 cm, and the estimated average weights 272.7, 43.7 and 135.2 g, respectively. The estimated average density of fish resources in Lake Jingpo was 2052, 2835 and 3313 t in spring, summer and autumn, respectively. The results of redundancy analysis between the fish density and environmental factors in Lake Jingpo showed that the total suspended solids, chlorophyll-a, water temperature and dissolved oxygen were the key environmental factors affecting the changes of fish community structure. According to the results of hydroacoustic and gillnet survey, the problem of miniaturization of catches in Lake Jingpo is prominent, and the fish resources are declining. Irrational utilization is the main factor resulting in the decline of fishery resources in Lake Jingpo. We recommend the relevant authorities strengthen the management of natural fishing strictly control the number and size of fishing, ensure the natural proliferation of fish resources, and integrate the pollution control of the Mudanjiang River Basin and the improvement of fish habitat environment and other fish habitat restoration measures, in order to promote the recovery of fishery resources.

Impact of spring freshet flooding and summer rainfall flooding on the water quality of an alpine\xa0barrier lake

BackgroundBarrier lakes, formed by river interception, are particularly influenced by the upstream river. As such, spring freshet flooding and summer rainfall flooding due to wet precipitation (e.g. snow and rainfall) may sharply increase the concentrations of nitrogen, phosphorous, and carbon compounds in barrier lakes. Too much nutrients will lead to lake eutrophication. In this study, we used Lake Jingpo, the world’s second largest alpine barrier lake, to examine the impact of spring freshet flooding and summer rainfall flooding on its water quality by building a hydrodynamic water quality model with MIKE 21.ResultsThe MIKE 21 HD hydrodynamic model and MIKE 21 AD convection and diffusion module were calibrated using meteorological data, hydrological data, and water quality data collected in 2018. All errors were in the acceptable range. According to model simulation results, the flow velocity in Lake Jingpo is generally weak (mostly lower than 0.015 m/s), but it increases to 0.045 m/s and above during spring freshet flooding (April–May) and summer rainfall flooding (August–September), which is much higher than in other months. The flow volume of its largest inflowing river reaches 4.81 × 108 m3, 29.77 × 108 m3, and 58.4 × 108 m3 during spring freshet flooding, summer rainfall flooding, and 30-year frequency rainfall flooding period, respectively. The longest diffusion distances from the lake mouth to the downstream way are 16.3 km, 33.1 km, and 43.6 km during the spring freshet flooding, summer rainfall flooding, and 30-year frequency rainfall flooding period, respectively. A larger amount of precipitation leads to longer diffusion distances and increased concentrations of total nitrogen (TN), total phosphorous (TP), chemical oxygen demand (CODMn), and ammonia–nitrogen (NH4-N) in the lake.ConclusionsThe sudden increase in water volume during spring flooding and summer rainfall flooding led to the rapid spread of nutrients and pollutants carried by the water into the barrier lake, resulting in a deterioration of lake water quality. In addition to pollution source control measures, ecological restoration, and the construction of a buffer system in the catchment are very important measures to effectively improve the buffer capacity of barrier lakes in light of spring freshet flooding and summer rainfall flooding.

Development and evaluation of a Planktonic Integrity Index (PII) for Jingpo Lake, China

A Planktonic Integrity Index (PII) for the China’s largest alpine barrier lake (Jingpo Lake) was developed to assess the water quality of Jingpo Lake by using phytoplankton and zooplankton metrics. Phytoplankton and zooplankton assemblages were sampled at 26 sites in Jingpo Lake. A total of 140 species of phytoplankton and 92 species of zooplankton were obtained in the investigations. We used a stepwise process to evaluate properties of candidate metrics and selected five for the PII: Algal cell abundance, Species richness of algae, Trophic diatom index, Zooplankton Shannon index, and Zooplankton Margalef index. Evaluation of the PII showed that it discriminated well between reference and impaired sites and the discriminatory biocriteria of the PII were suitable for the assessment of the water quality of Jingpo Lake. The further scoring results from the 26 sites showed that the water quality of Jingpo Lake was fair to good. The results of analyses between PII and major environmental factors indicated that water temperature (WT), transparency (SD), dissolved oxygen (DO), potassium permanganate (CODMn) and total nitrogen (TN) were the main factors influencing on the composition and distribution of phytoplankton and zooplankton. Additionally, more metrics belonging to habitat, hydrology, physics and chemistry should be considered for the PII, so as to establish comprehensive assessment system which can reflect the community structure of aquatic organisms, physical and chemical characteristics of water environment, human activities, etc.

东北镜泊湖硅藻对近现代气候变化和人类干扰的响应过程

PDF HTML阅读 XML下载 导出引用 引用提醒 东北镜泊湖硅藻对近现代气候变化和人类干扰的响应过程 DOI: 10.5846/stxb201610272185 作者: 作者单位: 浙江师范大学,中科院南京地理与湖泊研究所,浙江师范大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（41372184，41672173，41701218） Diatom response to climate changes and anthropogenic disturbances in Jingpo Lake (NE China) Author: Affiliation: Zhejiang Normal University,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:全球气候变暖和人类活动加剧已经导致中国大量湖泊生态系统功能退化，而目前对东北地区湖泊生态系统变化的认识主要源于短期的监测。以东北镜泊湖为例，通过沉积记录和现代监测资料，分析一个多世纪以来以硅藻群落为代表的湖泊生态系统对气候波动和区域人类活动的响应过程。研究结果表明，在人类干扰显著加强之前，风力扰动是镜泊湖硅藻群落变化的一个重要因子，表现为Aulacoseira属种取代小型浮游种（Cyclostephanos、Stephanodiscus和Discostella）成为优势种。20世纪70年代以来，Asterionella formosa、Nitzschia palea和Fragilaria crotonensis的相继增加则反映了流域农业活动加剧、农业化肥大量施用以及污水排放导致的湖泊营养水平升高。温度的持续上升已经引起东北地区一些湖泊硅藻群落结构发生显著变化，但镜泊湖的硅藻记录却未显示这一气候变化的信号。考虑湖泊-流域形态和人类活动的不同，研究认为近几十年气候变化对镜泊湖硅藻群落结构的影响被强烈的人类干扰所掩盖而未显现出来。 Abstract:Climate warming and intensified human activities have led to the deterioration of lake environments and the degradation of lake ecological services in China over the past few decades. In northeast (NE) China, up to now, information about lake ecological changes responding to climate changes and human activities has derived mainly from short-term observations. In the present study, we choose Jingpo Lake in NE China as the study area. Sediment records and paleolimnological methods, in combination with long-term meteorological observations, were used to determine the patterns of diatom community responses to climate changes and anthropogenic disturbances. The history of diatom assemblage changes over the past 130 years was reconstructed from the sediment of Jingpo Lake. The result was then compared with other diatom records from NE China to evaluate the impacts of climate changes and human activities on diatom community shifts. Our diatom records show a distinct shift from small-type planktonic species (e.g., Cyclostephanos dubius, Cyclostephanos tholiformis, Stephanodiscus parvus, Stephanodiscus invisitatus, Discostella pseudostelligera) to a genus of heavy frustules (Aulacoseira), implying that wind strength played an important role in diatom assemblage changes before the expansion of human activities. Since the end of the 1960s, successive increases in the abundance of Asterionella formosa, Nitzschia palea, and Fragilaria crotonensis have reflected intensified agricultural activities, fertilizer usage, and sewage discharge, which have resulted in a trend to eutrophication. The meteorological observations of the past 60 years reveal obvious climate warming in NE China, especially since the mid-1970s. Previous studies have shown that diatom communities in Lake Xiaolongwan and Erlongwan (NE China) have clearly responded to climate warming, while diatoms in Jingpo Lake have not responded in a similar way. Lake Xiaolongwan and Erlongwan have similar climate conditions to those at Jingpo Lake but much smaller basins and catchments. Additionally, human activities in the catchments of Lake Xiaolongwan and Erlongwan are much less intense. Therefore, it can be speculated that the impacts of climate warming on the diatom community shift in Jingpo Lake have been obscured by intense human disturbances. Additionally, intensified human activity has become the dominant factor leading to the ecological threshold being crossed in Jingpo Lake. 参考文献 相似文献 引证文献

Length-weight relationships for five fish species from Jingpo Lake, Heilongjiang, China

In this study the length–weight relationships for five fish species from Jingpo Lake in China belonging to three families and five genera were analyzed. A total of 368 specimens were used to estimate the relationship parameters. One species (Leuciscus waleckii) had no previous LWR estimate in FishBase.

Projecting the impact of climatic warming on coldwater fish habitat in Lake Jingpo

Climate warming would have a great impact on the water temperature and dissolved oxygen (DO) distribution of lakes in cold regions. It can have an effect on fish populations. To evaluate the effect of climatic change on coldwater fish habitat in cold regions of China, a fish habitat simulation model was developed. The fish habitat simulation model was developed based on the output of A vertical year-round water temperature and dissolved oxygen model. Lake Jingpo in Northeast China was chosen as the representive lake. The coldwater stenothermal fish called Hucho taimen was selected as the indicator species. Constant Values Method and oxythermal habitat parameter method were applied to identify the refuge habitat. The simulation results show that under the future climate scenarios, the uninhabitable space in winter due to low dissolved oxygen in hypolimnion will decrease, the uninhabitable space in summer due to high temperature in epilimnion will expand. Total habitat depth in summer is projected to decrease up to 60%-90%, which means high probability of summer kill. It is projected that multi-year average value of ATDO3 vb (highest average daily TDO3 over variable benchmark period) will have an increase of about 2.5℃, which means Hucho taimen juvenile survival rate will decrease about 35%. In the extreme warm year, the Hucho taimen juvenile survival rate will decrease to 9.0%. The oxythermal habitat parameter method is generic and can be applied to other lakes and reservoirs in Northeast China to identify and compare the refuge habitat of coldwater fishes.

Mid- to late-Holocene East Asian summer monsoon variability recorded in lacustrine sediments from Jingpo Lake, Northeastern China

The Northeastern China involves complex interactions between the East Asian summer monsoon (EASM) circulation and the polar climate system, and plays a significant role as the bridge communicating low- and high-latitude climatic processes. High-resolution multi-proxy analysis of a robust accelerator mass spectrometry (AMS) 14C dated lacustrine sediment core recovered from Jingpo Lake in Northeastern China provides a detailed history of EASM variability and vegetation changes since ~5100 cal. yr BP. The period from ~5100 to 3600 cal. yr BP was characterized by the highest pollen percentages of Quercus, Ulmus, Juglans and Corylopsis; low Md (median grain size diameter); and high δ13Corg values, reflecting a relatively warm and humid period. The period between ~3600 and 2100 cal. yr BP is characterized by high Md and low δ13Corg values, and a rapid increase in pollen percentages of herbs, indicating cool and dry climatic conditions. From ~2100 to 150 cal. yr BP, a gradual increase in δ13Corg values and low Md values, and a rapid increase in Carpinus, Juglans and Corylopsis pollen percentages was observed, indicating climate change towards warmer and wetter conditions. After ~150 cal. yr BP, the highest values of total organic carbon mass accumulation rate (TOC-MAR), total nitrogen mass accumulation rate (TN-MAR) and magnetic susceptibility suggesting that the Jingpo Lake region has been severely affected by human activities. The EASM variability in Northeastern China during the mid- to late Holocene shows trends similar to EASM records in China. Furthermore, our findings indicate that the variability of the EASM during the mid- to late Holocene on the multi-decadal to centennial scale was forced by changes in both solar output and oceanic–atmospheric circulation interaction.

Diatom-based inference of variations in the strength of East Asian spring wind speeds since mid-Holocene

Lake Jingpo is located in Ning'an County, Southeast Heilongjiang Province, northeast China and is strongly influenced by the East Asian monsoon system. Diatom analysis of the last 5000cal.yr BP according to the results of AMS 14C dating provides a detailed history of paleoenvironment changes. The relative abundance of diatom species, Asterionella formosa, Aulacoseira, Cyclostephanos, Stephanodiscus and Discostella species can be used as a proxy of spring wind speed, which is supported by the results of seasonal diatom and reviews of literature on the autoecologies of these species. In the sediment, high relative abundance of A. formosa, Aulacoseira species indicates high wind-driven turbulence of the water column. The diatom record of the past 5000years shows that the spring wind speed shifted from weak to strong to weak. In our result, the relative abundance of Aulacoseira species decreased sharply, while that of small-cell Cyclotella sensu lato (including Stephanodiscus, Cyclostephanos and Discostella) increased since 2000cal.yr BP. The broad alternations between these species are probably keyed to mean temperature and wind variations that control lake circulation and stratification. Our results support the hypotheses that abiotic drivers affect the size structure of planktonic communities and that a warmer climate favors small-sized diatom cells. The change in the ratio of A. formosa and Aulacoseira species to Cyclostephanos, Stephanodiscus and Discostella species (AA/SC) basically correspond to change of the spring insolation (May) at 45°N. Abundance of diatoms in Lake Jingpo roughly corresponds to changes in the Mid- to Low-Latitude Circulation Index of the northern hemisphere as indicated by NH4+ concentration from the GISP2 ice-core, the strength of the Asian summer monsoon as recorded from Hani Peat in Northeastern China, and from a stalagmite found in the Dongge cave in southern China. The results are important in demonstrating the sensitivity of diatoms to climate change, and providing proxy evidence for spring wind speed marked by shifts of diatom type.

Dynamic investigation on the co-infection status of two pathogens in ticks from tourist point in Heilongjiang province

To monitor the co-infection status of Borrelia burgdorferi sensu lato (B.b.s.l) and spotted fever group Rickettsia (SFGR) in tourist areas of Heilongjiang province. Polymerase chain reaction (PCR) was used to detect the 5S-23S rRNA intergenic spacer of B.b.s.l and ompA of SFGR in ticks, dynamically collected from tourist areas of Heilongjiang province in 2010. Amplification products from positive ticks were sequenced, and phylogenetic analysis was conducted by Mega 5.0 software package. 849 ticks were collected from two tourist points, with the dominant ticks in Tiger Mountain and Jingpo Lake were Ixodes persulcatus and Haemaphysalis concinna. Regarding the Ixodes persulcatus from Tiger Mountain, the infection rates of B.b.s.l and SFGR were 26.15% and 10.05%. The infection rate of SFGR was 13.33% in Haemaphysalis concinna and the B.b.s.l was undiscovered in the same ticks from Jingpo Lake. However, the co-infection could only be detected in Ixodes persulcatus of both tourist areas. Surveillance data showed that the major ticks were more likely to be appeared in July at Tiger Mountain and in June at Jingpo Lake. Data from the sequence analysis on B.b.s.l showed that the B.b.s.l in tourist areas could be classified into three different genotypes, other than B. garinii and B. afzelii. We first detected B. valaisiana-like group genotype in northeast of China. Results from the sequence analysis of SFGR positive products showed that the two DNA sequences of newly detected agents were completely the same as Rickettsia sp. HL-93 which was detected in Hulin and Rickettsia sp. H820 found in northeast, China. The co-infection of B.b.s.l and SFGR was detected in ticks from the tourist areas of Heilongjiang province, and data from the sequencing of specific fragment showed that various kinds of genotypes existed in this area. However; the rates of co-infections-different according to environment, time and population that contributed to the kinds of and the index of ticks existed in the surveys points, also the infection rate of the ticks was studied.

镜泊湖岩溶台地不同植被类型土壤微生物群落特征

To investigate the soil microbial characteristics under different successional stages at the Holocene-Basalt Platform,Jingpo Lake area,Northeast China,we carried out the research under six typical vegetation types,i.e.herbs,dwarf shrubs,highbush,shrubs mixed with small trees,deciduous broadleaf and conifer mixed with broadleaf.We conducted plant community survey,and measured soil physiochemical properties,soil microbial biomass,community-level substrate utilization characteristics(BIOLOG EcoPlatesTM) and microbial community structure(Phospholipid Fatty Acid Profiles PLFA).Significant differences existed among vegetation types.Under herb soil(in the early stage of succession),microbial biomass carbon(MBC),microbial biomass nitrogen(MBN),bacterial biomass,fungal biomass,metabolic activity(Average Well Color Development,AWCD) and the richness index were the lowest,while the Shannon-Wiener Diversity index was significantly(P0.05) higher than other vegetation types.The structure of soil microbial community was influenced by dwarf shrub.Dwarf shrub soil had the highest actinomycete biomass(34.2 nmol/g),which might be relevant to the dominant leguminous shrub species,Lespedeza daurica.Highbush soil and shrub mixed with small tree soil were similar in microbial biomass,PLFA composition,metabolic activity,functional diversity indexes,and slight difference existed in types of carbon sources utilized.Deciduous and broadleaf soil had the highest metabolic activity,richness index and ability of carbon utilization,which was in accordance with its high total microbial biomass and bacterial biomass.At the final stage of succession,fungal biomass of conifer mixed with broadleaf soil increased,and soil pH was the lowest.Vegetation might mediate soil microbial functional diversity by effecting soil phosphorous and soil organic carbon in our study.However,there were no significant(P0.05) relationship between herb layer diversity and soil microbial functional diversity,and further studies were needed to recover the complex interactions between herb layer and soil microbial functional diversity.

The paleo-precipitation history recorded by the characteristics of grain-size of Lake Jingpo during Holocene

在湖泊沉积与环境演变研究中,粒度参数通常用来反映湖泊水动力条件的变化,进而反映湖面波动状况以及湖区环境有效湿度的变化.镜泊湖JPH-1钻孔沉积物粒度分析表明:全新世以来镜泊湖沉积物粒度的变化呈现明显的粗细交替变化的规律性.结合14C测年,镜泊湖沉积物粒度特征有效地指示了历史时期镜泊湖水动力变化的情况.进而揭示了该地区古降水的变化历史.9300-8540cal aBP,是一个降水较少的偏干旱时期;8540-6350 cal aBP,降水颇丰的湿润时期; 6350-3120cal aBF,气候波动频繁,前期(6350-4800 cal aBP)由湿润向干旱过渡,后期(4800-3120cal aBP左右)又由于早转向湿润,31 20-1 580 cal aBP,降水较多,气候湿润;1 580 cal aBP至今,降水变化波动剧烈,这阶段粒度特征的变化除了与降水的自然变化有关外,还与人类活动的剧烈影响有关系.湖区周围人类活动破坏了原始植被,大量地表裸露,降水冲刷地表作用明显增大,陆源物质被携带人湖,粗颗粒含量显著增多.;Grain-size composition of lacuslrine sediment is a powerful indioalor to water impelus change and humi(i variation in ihe history. Based on the analyses on ihe grain-size composition characteristics of JPH-1 core,from Lake Jingpo, norlh eastern of China, combined with 14 C age sequence, ihe Holocene hist or) of paleo-preripilation changes in this region can be concluded as below:(1)9300-8540 cat aBP was a relatively dry period acromf)a-nied wilh less preripilation. (2) 8540-6350 cal aBP was a high lake level period, when the precipitation was relatively abundanlo. (3) 6350 -4800 cal aBP, the climate became drought graduaHy. (4) 4800 -3120 ral aBP, the climate changed wel again. (5) 3120-1580 cal aBP was a relatively slable period maintained a high lake level wilh abundant precipitation. (6) 1580 t.al aBP-present, il was an another climalioally oscillation f>eriod in which the precipitation has been changing frequently. In recent cenluries,the human activities, such as i leariiig the forest, destroying the original vegetation in lake watershed resulted in massive exposure of land surface, remarkable increase of erosion and more terrestrial maleriel carried into lake. Therefore, the portion of coarser particles increased markedly.