Reconstructing riverine paleo-flow regimes using subfossil insects (Coleoptera and Trichoptera): the application of the LIFE methodology to paleochannel sediments

Sub-fossil insect remains have the potential to characterise changing environmental conditions in both lentic and lotic water systems, however, relatively few studies have been undertaken in riverine environments. This paper uses sub-fossil caddisfly larvae (Trichoptera) and aquatic beetles (Coleoptera) to reconstruct river flow conditions for a large paleochannel (from multiple monoliths) using the Lotic invertebrate Index for Flow Evaluation (LIFE). Examination of the larval Trichoptera and Coleoptera remains indicated a marked change in the community and flow environment, as suggested by paleoLIFE scores within the profile of three of the monoliths examined. At the base of the channel the community was characterised by taxa indicative of high energy lotic habitats with predominantly mineral substrates (e.g. Trichoptera: Hydropsyche contubernalis and Brachycentrus subnubilis, Coleoptera: Elmis aenea and Esolus parallelepipedus). Within three of the monoliths there was a change in community composition to one indicative of a low energy backwater/lentic environment with abundant submerged and emergent vegetation (e.g. Trichoptera: Phryganea bipunctata and Limnephilus flavicornis, Coleoptera: Colymbetes fuscus and Hydrobius fuscipes). Detrended Correspondence Analysis (DCA) and loss of mass on ignition (LOI) indicated the presence of a strong environmental gradient within the data, associated with river flow. The utilisation of two aquatic insect orders provides clear evidence of temporal changes within the instream community and when combined with knowledge of ecological and habitat associations, allows differences between the two groups to be interpreted more clearly.     

Sciaridae in lake sediments: indicators of catchment and stream contribution to fossil insect assemblages

The larval head capsules of Sciaridae (black fungus gnats) are transported into lakes from terrestrial habitats, in most cases via streams or rivers, and preserve well in lake sediments. The abundance of sciarid remains can provide information on the importance of terrestrial and running-water input into fossil insect assemblages in lake sediments if examined in relation to the number of fossils of aquatic insects such as the Chironomidae, Thaumaleidae, Ceratopogonidae, or Simuliidae. Here we describe fossil head capsules of sciarid larvae and provide an example of how these remains can be used to constrain past changes in taphonomic processes that influence fossil chironomid records.     

Factors affecting the interpretation of caddisfly assemblages from Quaternary sediments

The use of assemblages of caddisflies (Trichoptera) in paleoecology has been explored over the past ca. 12 years. During this time, sites in North America, Great Britain and Europe have been studied and progress has been made in both the mechanics of identification and in the understanding of factors relevant to the interpretation of assemblages of this wholly aquatic group. Quaternary caddisfly fossils are abundant and usually well-preserved in waterlaid sediments. Individual larval sclerites can be identified by reference to shapes, textures, colour patterns muscle scar patterns and setal distributions. The flat frontoclypeus is particularly easily identified.Study of the biological and distributional data relevant to a caddisfly assemblage yields information at two levels. First the probable local habitat and second the climate can be described. This information is derived from both modern collections and the literature as the morphology of species, and hence it is assumed their environmental requirements, have not changed during the Quaternary. Comparisons with fossil assemblages of other plant and animal groups suggest that there are important factors to be considered in interpreting caddisfly assemblages, particularly those from sediments deposited during cold periods: for example, caddisflies may be slower to migrate than certain terrestrial insects, in particular the beetles (Coleoptera), and some glacial assemblages may therefore be dominated by hangers on. Lotic and lentic species also may migrate at different rates.Although caddisflies have not yet been fully exploited as paleoecological indicators, they have already contributed to our understanding of past environments and warrant much greater use.     

The development of the aquatic ecosystem at Kråkenes Lake, western Norway, during the late glacial and early Holocene - a synthesis

This paper synthesises the palaeoecological reconstructions, including palaeoclimatic inferences, based on the available fossil record of plants (pollen, macrofossils, mosses, diatoms) and animals (chironomids, Cladocera, Coleoptera, Trichoptera, oribatid mites) in the late-glacial and early-Holocene sediments of Kråkenes Lake, western Norway, with special emphasis on changes in the aquatic ecosystem. New percentage and influx pollen diagrams for selected taxa provide insights into the terrestrial setting. The information from all the proxies is collated in a stratigraphical chart, and the inferred changes in the lake and its catchment are discussed. The individual fossil sequences are summarised by detrended correspondence analysis (DCA), and sample scores on the first DCA axes are plotted against an estimated calendar-year timescale for comparison of the timing and magnitude of changes in assemblage composition. The DCA plots show that the large late-glacial biotic changes were synchronous, and were driven by the overriding forcing factor of temperature. During the early Holocene, however, the changes in different groups were more gradual and were independent of each other, showing that other factors were important and interactive, such as the inwash of dissolved and particulate material from the catchment, the base and nutrient status of the lake-water, and the internal processes of ecosystem succession and sediment accumulation. This multi-disciplinary study, with proxies for changes in the lake and in the catchment, highlights the dependence of lake biota and processes not only on regional climatic changes but also on changes in the lake catchment and on internal processes within the lake. Rates of change for each group are also estimated and compared. The reaction times to the sharp temperature changes at the start and end of the Younger Dryas were very rapid and occurred within a decade of the temperature change. Aquatic organisms tracked the temperature and environmental changes very closely, and are probably the best recorders of late-glacial climatic change in the fossil record.     

Pond biodiversity and habitat loss in the UK

Ponds are common landscape features but have been poorly studied compared to other freshwater habitats in the UK, despite their high frequency of occurrence. In the last century, many ponds have been lost and those that remain face increasing pressure due to agricultural land drainage, pollution and urban development. However, ponds provide important habitats for diverse floral and faunal communities, including a number of rare taxa of conservation interest. This paper examines the biodiversity and wider environmental value of ponds, with particular reference to the aquatic invertebrate and amphibian communities they support, and the adverse impact of anthropogenic activity on their aquatic habitats.     

山西云顶山亚高山草甸群落生态分析

应用双向指示种分析法 (TWINSPAN )和除趋势对应分析 (DCA )等数量分析方法,对山西云顶山亚高山草甸生态关系进行了研究,将该草甸划分为5个群落类型,分别位于不同的海拔高度。分类结果很好地反映了植物群落类型及优势种的分布与环境因子之间的关系,并在DCA二维排序图上得到了较好的验证。DCA排序轴反映了海拔高度、放牧强度和群落土壤湿度的梯度变化,表明海拔高度和水热条件是影响植物群落变化的主要环境因子,物种多样性在群落类型分化中有重要作用,同时放牧对亚高山草甸演替过程的干扰明显。     

Response of littoral chironomid communities and organic matter to late glacial lake—level,vegetation and climate changes at Lago dell’Accesa (Tuscany,Italy)

This study focuses on the response of lacustrine littoral chironomid communities to late glacial changes in limnological, environmental and climate conditions in the Mediterranean context. Late glacial chironomid (Diptera: Chironomidae) assemblages, organic petrography and geochemistry were analysed in a sediment core from the littoral zone of Lago dell’Accesa (Tuscany, Italy), where the lake-level fluctuations and the vegetation history have been previously reconstructed. Comparison of the chironomid stratigraphy to other proxies (pollen assemblages, organic petrography and geochemistry, lake-level) and regional climate reconstruction suggested the predominant influence of lake-level changes on the littoral chironomid fauna. The main lowering events that occurred during the Oldest and the Younger Dryas were followed by higher proportions of taxa typical of littoral habitats. A complementary study of organic matter suggested the indirect impact of lake-level on the chironomids through changes in humic status and habitat characteristics, such as the type of substrate and aquatic macrophyte development. Several chironomid taxa, such as Glyptotendipes, Microtendipes and Cricotopus type patens, were identified as possible indicators of low lake-level in the late glacial records. Nevertheless, this study suggested that parallel analyses of organic matter and chironomid assemblages may be needed to circumvent misinterpretation of littoral chironomid assemblage stratigraphy. There was a weak response of the chironomid assemblages to small lake-level lowerings that corresponded to the Older Dryas and Preboreal oscillations. A higher level of determination, e.g. to the species group level, may be necessary to increase the sensibility of the indicators to lake-level changes.     

太湖流域水生态功能三级分区

水生态功能分区是进行流域现代水生态管理的必然要求,是面向水质目标管理控制单元划分的基础。针对太湖流域特征,提出了太湖流域水生态功能三级分区的目的和划分原则,在其指导下构建了太湖流域非太湖湖体区和太湖湖体区水生态功能三级分区指标体系;在GIS技术支撑下,分别以太湖流域非太湖湖体区1100多个和太湖湖体区3500多个水生态功能单元为基本空间统计单位,结合分区指标数据,制作了基于水生态功能单元的各项指标的空间分布图,采用二阶聚类法并结合人工辅助的方法将太湖流域划分为21个水生态功能三级区;分区水生态特征分析结果表明全流域各分区水生生物特征均具有较大的变异性,反映出流域内水生态的空间差异和不均匀性,体现了分区结果的合理性、科学性和可靠性。     

Intra-lake patterns of aquatic insect and mite remains

Surface sediment samples from Lake Moaralmsee in the Austrian Alps were examined for fossil remains of aquatic insects and mites. This study investigated the influence of water depth on the fauna, to explore the possibility of using such fossil remains in sediment cores to reconstruct past water level changes. In addition, instar-specific patterns of chironomid (Diptera: Chironomidae) head capsule accumulation were examined to evaluate whether the smaller, lighter-weight early instars are more easily transported within the lake basin, creating a potential source of error for paleolimnological inferences. Results showed that intra-lake distribution of these zoological remains is closely related to water depth and suggested that the fossils accumulate near each species’ habitat. In addition, the ratio between exoskeletons of oribatid mites (Acari: Oribatida) and chironomid head capsules was strongly related to water depth. Examination of instar-specific accumulation patterns of all chironomid remains showed no significant relationship between specific instars and water depth, though littoral samples consisted only of the 3rd and 4th instars. A taxon-specific examination revealed that the early instars of Paracladius are significantly focused to the deeper parts of the basin. Because most taxa displayed significant relations with water depth, a transfer function was developed, relating fossil chironomids to water depth. This model has a high coefficient of determination and a low estimate of prediction error. In this study, Paracladius was found to prefer shallow and intermediate water depths, hence enhanced offshore transport of early instar head capsules may weaken model performance statistics. Results indicate that intra-lake calibration sets of invertebrate remains have great potential in paleolimnological research, though there is a possible risk of spatial autocorrelation. Such datasets also contribute to the understanding of the modern ecology of the fauna because fossil assemblages in surface deposits provide habitat-specific autecological information. More effort should be directed at evaluating how remains of different instars are transported within other lake basins, because selective offshore transport of head capsules of different larval stages can potentially cause bias in environmental reconstructions.     

山西天龙山植被及植物资源

采用TWINSPAN对天龙山主要植被进行了分类 ,并用DCA方法分析了植物群落间的生态关系 ,描述了九个主要植物群落类型的特征 ,最后介绍了蕴藏于植被中的天然植物资源的类型及其经济用途 ,提出了植物资源开发利用的对策。     

建三江农垦分局湿地植物群落分类和排序

采用双指示种分析（Two Way Indicators Species Analysis,TWINSPAN）和除趋势对应分析（Detrended Correspondence Analysis,DCA）方法,对位于三江平原的建三江农垦分局内的湿地植物群落的数据进行群落数量分类和排序。调查的86个样地中共发现49科133属226个物种;TWINSPAN将样地划分为8种群丛,将优势物种划分为8组,分类结果可以在DCA排序图上很好地反映出来,且优势物种的分布格局很大程度上决定了群丛的分布格局;DCA的前两个排序轴提供了23．5％的信息量,其中第一排序轴提供了14．5％的信息量,主要反映出样地水分条件的变化;样地的排序结果反映了植物群落类型与环境因子之间的关系。     

历山山地草甸的生态关系

以山西历山的舜王坪草甸为研究地，运用TWINSPAN和DCA相结合的数量生态方法对9个群落进行划分，得到一个明显的随放牧强度变化的群落序列，即从群落Ⅲ、Ⅳ到群落Ⅴ、Ⅵ再到群落Ⅷ，分别为过牧阶段、中牧阶段和轻牧阶段。可见，利用TWINSPAN和DCA相结合可对不同放牧强度的群落进行划分和排序。从草甸的生态关系研究得出历山山地草甸退化的主要原因是人为干扰。运用DCCA排序法，综合样方和土壤环境因子信息，定量综合研究了放牧草甸与周围土壤环境的生态关系。DCCA第一轴也表现为放牧梯度，在过牧阶段的群落中，有机质和N的含量较高，土壤的退化滞后于植被资源的退化；而在轻牧阶段的群落中，营养元素含量较高。     

适用于遥感影像的水生态空间多功能分类体系研究

水生态空间分类体系是研究水生态空间变化的重要前提。目前,水生态空间分类体系一般都基于特定的研究或者管理目的,没有相对统一的划定标准。因此,这些水生态空间分类体系间的可比性及可操作性就存在一定的局限。鉴于此,论文结合遥感观测技术,基于系统论提出了适用于遥感影像的水生态空间多功能分类体系。该分类体系具有一定的理论基础,同时也兼具遥感技术的可操作性和可比性,能为研究水生态空间的面积动态变化提供理论基础和技术保障。此外,研究还结合生产管理经验和专家咨询等方法,建立了适用于Landsat卫星遥感数据的各类水生态空间的解译标志。最后,以中国为例,运用2015年的Landsat卫星遥感数据,划定了中国各类水生态空间的分布,并得到了不同水生态空间类型所占的面积比,这为进一步研究中国水生态空间的演化规律奠定了坚实基础。     

基于无人机遥感的古银叶树群落健康快速诊断

采用无人机低空遥感与地面调查相结合的方法对邻海陆地、远海陆地和盐生沼泽生境的古银叶树群落健康进行评价，利用冠层高度、林窗特征、光合有效辐射截面比、归一化植被指数（NDVI）、氮素反射指数（NRI）、黄色波段指数（YI）以及森林健康指数（FHI）等遥感指标指征古银叶树群落的健康状况。空-地结合的调查结果表明：1）盐生沼泽生境的古树由于树龄高，其树洞大且数量多，生境内生物多样性最低，邻海陆地生境的生物多样性最高。2）盐生沼泽生境的冠层高度最低；林窗面积最大，数量最少，形状复杂度最低；光合有效辐射截面比最小。以上指标在邻海陆地和远海陆地间差异不明显。NDVI、NRI、YI以及FHI的数值均表现出盐生沼泽小于远海陆地和邻海陆地的趋势，而在远海陆地和邻海陆地间的差异较小。3）无人机遥感的评价结果与地面调查结果契合度较高，客观地反映了不同生境古银叶树的健康状态。基于无人机遥感的评价体系在针对具体植物群落修改完善后，可以作为一种快速、无损和定量化的古树群落健康诊断方法。     

A late Holocene palaeolimnological record from central Mexico, based on faunal and stable-isotope analysis of ostracod shells

A late Holocene palaeolimnological record for central Mexico has been obtained from Lake Pátzcuaro, using recent and fossil ostracods. Lake Pátzcuaro, Michoacán, is a closed-basin lake which responds rapidly to changes in the ratio of precipitation/evaporation in the region. The record from a single lake-sediment core, dated by AMS radiocarbon method, covers the last ~3,530 yrs, and is based on ostracod faunal palaeoecology coupled with analysis of the stable-isotope (¹⁸O/¹⁶O and ¹³C/¹²C) composition of ostracod valves. The faunal distribution is determined by the presence or absence of aquatic vegetation and, to a lesser extent, salinity. The ¹⁸O/¹⁶O and ¹³C/¹²C ratios in ostracod calcite show good agreement with palaeolimnological inferences from the faunal assemblages, principally recording changing precipitation/evaporation and primary-productivity levels, respectively. Wetter conditions existed in central Mexico between approximately ~3,600 and ~2,390 yr BP, between ~1,330 to ~1,120 yr BP, and from ~220 yr BP to present, characterised by fluctuating lake levels. A dilution of the sediment load in the lake reduced turbidity levels allowing for a marked increase in productivity. During these phases, the combination of a deeper lake and increased macrophyte cover reduced the degree of mixing of the waterbody. In the earliest of these phases there was sufficient stratification of the waterbody for methanogenesis to occur in the sediment interstices. The wet phases were separated by prolonged dry periods, during which time the climatic conditions were relatively stable. Good agreement was found between the findings of this study and others from the central Mexican/Caribbean region suggesting that abrupt climate changes occurred at least at a regional scale.     

Sub-fossil Chironomidae from East Africa. 2. Chironominae (Chironomini and Tanytarsini)

This paper and a companion article present illustrated guides to the identification of sub-fossil chironomid larvae (Insecta: Diptera: Chironomidae) preserved in the sediments of low- and mid-elevation lakes in East Africa. They are based on analysis of surface-sediment death assemblages from 61 lakes located in the humid to semi-arid environments in equatorial East Africa (Uganda, Kenya, Tanzania), supplemented with similar surface-sediment samples from 12 lakes in the Horn of Africa (Ethiopia), and sub-recent core samples from six lakes in Kenya and two in Uganda. We analyzed about 11,000 specimens and identified 98.4% of these to species, species group, genus, or tribe level, depending on current -taxonomic knowledge of the various considered genera and the taxonomic resolution of preserved diagnostic features. We distinguished 90 different sub-fossil morphotypes, of which 16 are Tanypodinae, 19 are Orthocladiinae, and 55 are Chironominae. In this paper we focus on the subfamily Chironominae (tribes Chironomini and Tanytarsini). The diagnostic characters distinguishing these morphotypes from each other resemble differences at the species level in the better-known Holarctic fauna, hence we consider most of our morphotypes equivalent to morphological species or groups of closely related species. Given that core samples yielded only seven morphotypes not also found in the surface-sediment samples, the current inventory of 90 taxa likely represents the large majority of distinct sub-fossil chironomid larval types to be found in East African lakes, excluding the few very large Rift lakes, cold-water lakes above treeline, and special standing-water environments such as fens and bogs. Consistent use of a single set of morphological characters to identify both fossil and living chironomid larvae would ensure exchangeability of information between modem and paleoenvironmental studies on aquatic invertebrate communities in African lakes, and increase the relevance of paleoenvironmental reconstructions to water-quality evaluations aimed at sustainable management of scarce, fluctuating surface-water resources in tropical East Africa.     

长江口北支湿地鸟类多样性研究 Ⅱ.水鸟群落多样性研究

野外实地调查表明,光滩、藻类盐渍带-藨草、海三棱藨草带-芦苇带-堤内养殖塘4种典型湿地生境是长江口北支湿地水鸟的主要活动区域。光滩、藻类盐渍带中水鸟的种类和数量均最多,其次为堤内养殖塘和藨草、海三棱藨草带,芦苇带中水鸟的种类和数量均最少,食源状况是导致不同生境中水鸟群落分布差异的主要原因。在4种典型湿地生境中,鸟类群落的物种多样性和均匀度均存在差异,但总体上差异不明显,物种多样性均处在中等偏上水平,而均匀度普遍较低。光滩、藻类盐渍带与堤内养殖塘水鸟群落的相似性最高,相似性指数高达0.697;芦苇带与其他3种生境中水鸟群落的相似性均很低,相似性指数均不大于0.257。表明芦苇带与其他3种生境中水鸟群落组成有较大差异。     

Oribatid mite assemblages across the tree-line in western Norway and their representation in lake sediments

Little is known about the relationships between fossil oribatid mite assemblages in lake and mire sediments and the composition, abundance, and richness of their living communities. Because oribatid mites are a relatively new area of palaeolimnological study, there is a great lack of knowledge about the taphonomic processes that might affect fossil mite assemblages. The DOORMAT (Direct Observation Of Recent Macrofossils Across Tree-line) project was designed to study the transport and deposition of oribatid mites and plant remains in the tree-line area of western Norway. The present study also compares modern oribatid assemblages with fossil oribatid assemblages in a Holocene lake-sediment sequence from the nearby Trettetj?rn, and considers the optimal location for studying fossil oribatid mites within a lake basin. Seven novel terrestrial traps (50 × 80 cm Astroturf doormats) were placed at major vegetational transitions along an altitudinal transect crossing the tree-line ecotone from 633 to 1,120 m a.s.l. at Upsete, west Norway. Three sediment traps were placed in Trettetj?rn (810 m a.sl.) at the inlet, the middle, and near the outlet. In each terrestrial trap, the oribatid assemblage was found to be characteristic of the surrounding habitat. The lake-trap analyses showed that aquatic or moist-habitat species had the highest chance of being incorporated into the lake sediments; the number of terrestrial species decreased considerably from both outlet and inlet traps to the central trap in the deepest water. The area adjacent to the inlet of Trettetj?rn would therefore be the optimal location for a sediment core for oribatid analysis. However, this conclusion is not supported when the modern trap results are compared with the Trettetj?rn sequence from the lake centre.