Comparison of fish communities using environmental DNA metabarcoding and capture methods in a plateau Erhai Lake,China

Environmental DNA(eDNA)has been used as an important tool for fish diversity analysis,which can greatly solve the problems in traditional survey methodology.However,little work has been done on the actual monitoring accuracy of eDNA.In this study,we analyzed the current status of fish resources in Erhai Lake in Yunnan,SW China,by dividing the lake into three sectors according to habitat differences,and compared the results of eDNA and traditional capture methods to investigate the shortcomings of the current analysis of eDNA results.A total of 27 fish species were detected by eDNA and traditional capture methods,including 20 and 19 fish species,respectively,and additional differences in fish composition between the two methods.The alpha diversity showed higher fish abundance and lower fish diversity by eDNA method compared to the traditional capture method,demonstrating that eDNA was not superior for use in fish diversity analysis.Fish community similarity analysis showed that community differences were generally significant for eDNA(P<0.05).RDA analysis indicated that environmental factors did not significantly affect fish communities monitored by the eDNA method.However,water temperature,aquatic plants,and water depth had significant(P<0.05)effects on fish communities in the traditional capture method,suggesting that eDNA results are insensitive to the effects of environmental factors.Our results illustrate the effectiveness of eDNA in fish identification and the issues in quantification compared to traditional capture methods.Therefore,combining eDNA with traditional methods is a more effective method for analyzing eDNA metabarcoding,following which the protocols of both quantitative methods can be designed to explore the regularity of eDNA quantification.

Characteristics of Nitrogen and Phosphorus Losses in Different Crop Rotation Systems in the North of Erhai Lake Basin

[Objective] Nitrogen and phosphorus losses of surface runoff in various crop rotation systems in the north of Erhai Lake basin were studied with the objective to provide references for risk evaluation of environmental pollution and formulating countermeasures to control the nonpoint source pollution from agriculture.[Method] Water samples collected in four typical crop rotation systems distributed in seven towns（townships） in the north of Erhai Lake basin were investigated,as well as the fertilizer input,to explore the dynamic change of nitrogen and phosphorus content in surface water of farmland and ditch water,and the correlation between fertilizer input and the concentrations of nitrogen and phosphorus in the surface water of farmland and in the ditch water.[Result] The results showed that nitrogen loss in surface water of farmland in different crop rotation systems differed greatly,and the risk of nitrogen loss was 38% lower in broad bean-rice crop rotation than that in garlic-rice crop rotation.The water soluble nitrogen was the primary form of nitrogen loss.The content of water soluble nitrogen was significantly higher in garlic-rice crop rotation than that in the other rotation systems,and the concentrations of nitrogen in the surface water of farmland in different crop rotation systems followed the sequence below：garlic-rice crop rotationryegrass-rice crop rotationbroad bean-rice crop rotationrape-rice crop rotation.The loss of phosphorus in the surface water of farmland was relatively low and phosphorus combined with silt was the primary form for phosphorus loss.There was no significant difference of the loss of various forms of phosphorus in different crop rotation systems.The contents of total nitrogen and total phosphorus in the surface water of farmland were higher than that in ditch water,with increasing rates of total nitrogen and total phosphorus in ditch water of 72% and 82%,respectively.Topdressing was the critical reason for the high concentrations of nitrogen and phosphorus in the surface water,which also caused the increasing load to the ditch water.[Conclusion] Both the nitrogen and phosphorus loss were the highest in garlic-rice crop rotation.Reasonable crop rotation systems should be established based on both the environmental and economic benefits.This study provided references for controlling the nonpoint source pollution of farmland and improving the water quality of Erhai Lake.

Study on the Biological Diversity of Nematode-trapping Fungi in Erhai Lake

[Objective]The research aimed to investigate the biological diversity of nematode-trapping fungi in the sediment of Erhai Lake.[Method]616 pieces of sediments were collected from Erhai Lake.The traditional classification and identification methods were used to isolate,purify and identify.[Result]3 genera and 22 species of nematode-trapping fungi were isolated.Arthrobotrys oligospora,A.musiformis and Dactylella leptospora were the dominant species,and their detection rates were 28.05%,16.04% and 8.92% respectively.By analyzing the diversity of nematode-trapping fungi in four seasons,it was found that the biological diversity was richer in summer,spring and autumn,and the diversity indexes were 2.59,2.47 and 2.34 respectively.The diversity index in winter was 1.48 and was lower.Species forming the adhesive nets were predominant;positive rate was 41.00%.[Conclusion]The rich nematode-trapping fungi resource existed in Erhai Lake,and its biological diversity had the seasonal variation characteristic.The nematode-trapping fungi which formed the viscous net were the dominant species in Erhai Lake.

Seasonal dynamics of crustacean zooplankton community structure in Erhai Lake, a plateau lake, with reference to phytoplankton and environmental factors

The seasonal dynamics of a crustacean zooplankton community in Erhai Lake was investigated from May 2010 to April 2011. In total, 11 species were recorded, including six(6 genera) cladoceran and five(5 genera) copepod species. The crustacean zooplankton densities ranged from 24.3 to 155.4 ind./L. In winter and spring, the large-bodied cladoceran Daphnia galeata dominated the crustacean plankton community. In summer and autumn, when the colonial or filamentous algae dominated the phytoplankton communities, the small-bodied species(e.g. B osmina fatalis, Ceriodaphnia quadrangular, and Mesocyclops leuckarti) replaced the large-bodied ones. One-way ANOVA and redundancy analysis revealed that community structure was dependent upon total nitrogen, total phosphorus, water temperature, transparency, and the biomass of small algae. The variation in both phytoplankton structure and environmental variables were important factors in the seasonal succession of crustacean zooplankton structure in Erhai Lake.

Study on Environmental Risk and Economic Benefits of Rotation Systems in Farmland of Erhai Lake Basin

This study was designed to find out an optimised planting system of reducing non-point （source） pollution by analyzing the reasons and the factors of influence non-point pollution in farmland of Erhai Lake basin. The results showed that incomes, residual nitrogen in soil, and the loss of nitrogen in surface water in rice-garlic system were higher than those in rice-fava bean system. There were positive correlations between the nitrogen loss of farmland, nitrogen inputs, residual nitrogen in soil, and incomes of farmland. Economic benefits and environment benefits are both appropriate, if the area of rice-garlic system would be reduced to 53% and the area of rice-fava bean system increased to 36% of total cropping area in the investigated watershed. Adjustment of planting structure and introduction of reasonable rotation systems is considered an effective measure of controlling agricultural non-point pollution in watersheds of Erhai Lake.

Status and historical changes in the fish community in Erhai Lake

Erhai Lake is the second largest freshwater lake on the Yunnan Plateau, Southwest China. In recent decades, a number of exotic fish species have been introduced into the lake and the fish community has changed considerably. We evaluated the status of the fish community based on surveys with multimesh gillnet, trap net, and benthic fyke-net between May 2009 and April 2012. In addition, we evaluated the change in the community using historical data （1952-2010） describing the fish community and fishery harvest. The current fish community is dominated by small-sized fishes, including Pseudorasbora parva, Rhinogobius giurinus, Micropercops swinhonis, Hemiculter leucisculus, and Rhinogobius cliffordpopei. These accounted for 87.7% of the 22 546 total specimens collected. Omnivorous and carnivorous species dominated the community. A canonical correspondence analysis （CCA） plot revealed that the distribution of fishes in the lake is influenced by aquatic plants, water temperature, pH, and season. The abundance of indigenous species has declined sharply, and a majority of endemic species have been extirpated from the lake （a decrease from seven to two species）. In contrast, the number of exotic species has increased since the 1960s to a total of 22 at present. The fishery harvest decreased initially following the 1960s, but has since increased due to the introduction of non-native fish and stocking of native fish. The fishery harvest was significantly correlated with total nitrogen, not total phosphorus, during the past 20 years. Based on our results, we discuss recommendations for the restoration and conservation of the fish resources in Erhai Lake.

RECENT SEDIMENTATION AND SUSPENDED MATTER IN ERHAI LAKE,YUNNAN PROVINCE,CHINA

Ths study on the physico-geograpical environment of Erhai Lake focused on the suspended matter and recent deposition rates, 14 C, 210 Pb and 137 Cs methods were used to determine the ageand sedimentation rate, which was found to be 0.5 t0 2.0 mm/a, average of 0.9 mm/a. The authors calculated the budget of some elements by studying the deposition, and fuUnd that about 30% of nitrogen,and most of the phosphorous, were transported into the lake by the ediments.

Factors controlling the latent and sensible heat FLuxes over Erhai Lake under different atmospheric surface layer stability conditions

The stratification of the atmospheric surface layer(ASL)plays an important role in regulating the water vapor and heat exchange across the lake–air interface.Based on one year of data measured by the eddy covariance technique over Erhai Lake in 2015,the ASL stability(ζ)was divided into six ranges,including unstable(-1ζ<-0:1),weakly unstable(-0:1ζ<-0:01),near-neutral1(-0:01ζ<0),near-neutral2(0ζ<0:01),weakly stable(0:01ζ<0:1),and stable(0:1ζ<1).The characteristics of ASL stability conditions and factors controlling the latent(LE)and sensible heat(H)fluxes under different stability conditions were analyzed in this study.The stability conditions of Erhai Lake have noticeably seasonal and diurnal variation,with the nearneutral and(weakly)stable stratification usually occurring before July,with frequencies of 51.7%and 23.3%,respectively,but most of the(weakly)unstable stratification was observed after July,with a frequency of 59.8%.Large evaporation occurred even in stable atmospheric conditions,due to the coupled effects of the relatively larger lake–air vapor pressure difference and wind speed.The relative controls of LE and H by different atmospheric variables are largely dependent on the stability conditions.In stable and unstable ranges,LE is closely correlated with the vapor pressure difference,whereas in weakly unstable to weakly stable ranges,it is primarily controlled by wind speed.H is related to wind speed and the lake–air temperature difference under stable conditions,but shows no obvious relationship under unstable conditions.

Ectoparasite communities on Tupaia belangeri (Scandentia:Tupaiidae) in surrounding areas of Erhai Lake in Yunnan,China

Objective:To investigate the ectoparasite communities on Tupaia belangeri (T. belangeri) in the surrounding areas of Erhai Lake and their potential importance in medical and veterinary science. Methods: Different locations in surrounding areas of Erhai Lake in Yunnan were selected as the investigation spots. T. belangeri were randomly captured with baited mouse cages and then brought to the laboratory for identification according to their body shape, size and color, and measurements such as the lengths of their body, ear and hind feet. Ectoparasites on them were collected and identified to determine the species under microscope after specimens were mounted on slides, with the clearing and drying process completed. The constituent ratio (C), prevalence (P) and average ectoparasite abundance (A) were used to test the prevalence and density of ectoparasites; Non-parametric Mann-Whitney U-tests were used to test the differences in the abundance and richness of ectoparasites between female and male hosts; Spearman correlation analysis was used to analyze the relationship between ectoparasites and the body parameters of hosts. Results: There was very high species diversity of ectoparasites found on T. belangeri and some species of ectoparasites were reported associated with human diseases. A high proportion (88%) of 107 T. belangeri was found to be infested with ectoparasites. A total of 75 species of ectoparasites on them were collected, including 58 species of chigger mite, 12 species of gamasid mite, 4 species of flea and 1 species of sucking louse. Within this ectoparasite complex, 13 species were previously reported to be vectors of human disease agents. Non-parametric Mann-Whitney U-tests showed significant differences between male and female T. belangeri in terms of the abundance and richness of total ectoparasites. However, the species richness and abundance of chigger mites, sucking lice, fleas or gamasid mites presented no significant differences between male and female hosts. Spearman correlation analysis showed that none of correlations were observed between host body parameters with abundance and richness of total ectoparasites, chigger mites, suckinglice, fleas or gamatid mites. Conclusion: The results suggest that there is very high species diversity of ectoparasites on T. belangeri, consisting mainly of communities of sucking lice, fleas, chiggers and gamasid mites.

Analysis on the Space and Architecture of the Bai Settlement in Erhai Area Under the Influence of Han Culture

The influence of the Han culture on the Bai culture in Dali is the greatest and the most profound during the course of the historical development of China for thousands of years. The blending of the Han culture and the Bai culture is a distinctive feature the Bai culture, which is obviously seen in the location and layout as well as the composition and structure of the settlement and architecture of the Bai nationality in the Erhai area of Dali. Additionally, the Bai nationality in Erhai area conformed to nature and adopted nature to create the unique culture and settlement landscape based on the absorption of the cultural thoughts such as the golden mean, respect for seniority and the harmony between man and nature, as well as the advanced skills of the Han nationality. This paper further emphasized the characteristics and laws of Bai culture through the analysis of the Han culture elements in the space and architecture of the Bai settlement in the Erhai area of Dali. It is hoped that this study can provide references for the protection and development of the Bai settlement.

Carnivals between Cangshan Mountain and Erhai Lake

THE Bai people are China’s 15th largest ethnic minority.They live mainly in Yunnan Province,specifically in Dali Bai Autonomous Prefecture,and some in Guizhou and Hunan provinces.Dali is where the Bai people’s ethnic roots are.From the 23rd to 25th day of the fourth lunar month every year,Bai people in Dali pray for

Keep Erhai Lake Clean

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Sediment Particle Size Distribution and Its Environmental Significance in Lake Erhai, Yunnan Province

A closed or semi\|closed plateau lake, whose sediment records can provide us with plenty of fine and high resolution information, is a sensitive indicator of climatic and environmental changes. During the reconstruction of various short\|time\|scale climatic and environmental changes, the geochemical records in plateau\|lake sediments are superior to other natural files. Based on fine dissection of the vertical profile of sediment particle sizes, this paper reveals the quasi\|periodical changes of sediment particle sizes, which indicates the quasi\|periodical fluctuations of the regional climate. A synthetic analysis of multiple indexes shows that sediment particle size is a more sensitive and more effective index of climatic and environmental changes than other geochemical indexes. High content of >20 μm sediment particles and low content of 2-10 μm sediment particles indicate a warm\|dry climate and conversely a cold\|humid climate, and their ratio can be used as an effective index of climatic changes. The basic climate succession in the region of Lake Erhai is characterized as being alternatively warm\|dry and cold\|humid and it has been developing into a warm\|dry climate as a whole. There exist at least 2 time\|scale quasi\|periodical fluctuations of the regional climate in Lake Erhai. At present, the region of Lake Erhai is at the end of the warm\|dry period and at the beginning of a cold\|humid period, so the temperature will go down and the water level will rise.

控制性供水湖泊旱限水位确定方法——以洱海为例

旱限水位作为干旱预警以及工程抗预案的重要指标和依据,对科学指导湖泊开展抗旱调度具有重要的作用。本文针对控制性供水湖泊的特征,在充分考虑湖泊自身生态健康稳定的同时,结合湖泊兴利调节逆序递推计算,提出了一种控制性供水湖泊旱限水位计算方法,以洱海为例,验证了该方法的合理性。结果表明:通过设定旱限水位,在考虑湖泊最小生态需求的基础上,通过在干旱前期预留水量,可有效缓解干旱年份的湖泊周边地区的严重缺水情况;在设置旱限水位后,连旱最不利年份下洱海环湖供水缺水量减少1023万m^(3),引洱入宾农业灌溉用水减少1016万m^(3),环湖城市供水、引洱入宾灌溉严重缺水月数分别减少11、10个,低于最低生态水位月数减少15个。本研究为水旱灾害防御部门制定湖泊旱限水位、指导湖泊开展抗旱调度提供了一套通用算法,能够为干旱防御决策提供科学依据和技术支撑。

苍山洱海国家级自然保护区土地利用格局

目的:了解云南苍山洱海国家级自然保护区(以下简称“保护区”)土地利用结构及特征,掌握土地利用的景观格局,为保护区整合优化及后期管理提供指导。方法:以相关调查数据为基础,基于GIS技术,对保护区土地利用现状、景观格局及矛盾冲突进行分析。结果:苍山片区以林地和草地为主(面积占比96.43%),洱海片区以水体为主(面积占比98.02%);研究区域林地、水域和草地景观形状较为规整,景观破碎度较低,受人为干扰较少;保护区的景观多样性较丰富,但分布不均;保护区各类矛盾冲突图斑面积占保护区总面积的2.44%,矛盾冲突地块主要分布于缓冲区和实验区,以耕地和集体人工商品林为主,采矿用地、城镇建成区和村庄对保护区的影响程度最大。结论:保护区土地结构较为合理,苍山片区管理上要以森林防火、生物多样性保护、地质遗迹保护为主;洱海片区要以湿地保护,特别是水体质量维护和提升,以及水生动植物保护为主。

苍山洱海国家级自然保护区森林资源动态

目的:了解云南苍山洱海国家级自然保护区(以下简称“保护区”)森林资源近20年的动态变化特征,为保护区编制经营管理方案提供指导。方法:以2005、2015年森林资源调查矢量数据、2021年森林、草原、湿地监测数据、第三次全国土地调查数据为基础数据,基于GIS技术,分析保护区森林资源动态。结果:保护区土地利用类型中,有林地面积最大,并逐年增加;林地中,3个调查年度均以有林地和灌木林地为主,面积占保护区总面积的60.82%以上;保护区森林覆盖率2005—2015年间逐年增加,2015—2021年间增加值逐步趋于稳定;蓄积量以有林地蓄积为主,并逐年增加;乔木林地面积和蓄积量以栎类、云南松、华山松和苍山冷杉为主,且逐年增加;乔木林地中幼龄林、中龄林、近熟林和成熟林比重相对均衡,过熟林面积较少;各年度郁闭度等级均以中为主,且郁闭度等级为中和密的乔木林地面积和蓄积量均逐年增加。结论:保护区森林质量和生态防护功能逐年提高,后期森林资源管理以增加栎类等阔叶林为主。

南诏国的两个地震神话

南诏国(738—902)有两个地震神话传世:一为观音大士镇伏巨鳌,令其长眠不醒,但允其七十至九十春可醒片时。巨鳌醒时眨眼,仍会地动山摇,以致每七十余年地震一次,每四百年大震一次。因此,在望海台树立地震碑,告诫后人要警惕震害。二为洱海河神段赤诚预报地震:今夜亥时,地将大动,十室九倒。为保民平安,遂与两位山神、河东渔夫分工合作:两山神分别变化为鸡与犬,狂鸣、惊跳,以警醒万民;河东渔夫向洱海东部村民报告,洱海河神变化为老叟向西部村民报告。十有九成的村民离开房舍,避于平坦之地,人畜皆安;不相信预报的百余人,皆遭震害。

洱海周边面山植物区系特征调查研究

针对洱海周边面山选取了典型样地31个,采集到洱海周边面山植物475种,隶属于335属、121科。调查及标本鉴定结果表明:洱海面山带有维管束植物(除栽培)100科、294属、403种。其中蕨类植物8科15属21种;裸子植物1科1属1种;被子植物91科278属381种:其中单子叶植物16科63属82种;双子叶植物75科215属299种。对调查区的维管束植物科属区系组成进行分析,指出了植物科属泛热带和热带区系成分明显,这将为后期对洱海面山植被恢复选取树种提供参考,也为进一步加强洱海的保护及其合理开发利用提供理论依据。

典型挺水植物应用于湿地生态修复工程污染净化效应差异性研究

以洱海流域北部上游东湖片区库塘湿地中水生植物为研究对象,选取5种主要水生植物,寻求净化湿地水质的最佳植物组合。结果表明:东湖片区库塘湿地水体总磷、总氮、氨氮、化学需氧量分别为0.09~0.23、0.80~3.28、0.18~0.89、12.00~37.00 mg/L,总体符合《地表水环境质量标准》(GB 3838—2002)中Ⅳ类要求;综合比较发现,植物组合群落生物量和碳氮磷累积效应优于单一植物;植物组合对水体碳氮磷具有一定的吸收净化作用。