Abundance trends for river macroinvertebrates vary across taxa,trophic group and river typology

There is mounting evidence that terrestrial arthropods are declining rapidly in many areas of the world. It is unclear whether freshwater invertebrates, which are key providers of ecosystem services, are also declining. We addressed this question by analysing a long-term dataset of macroinvertebrate abundance collected from 2002 to 2019 across 5009 sampling sites in English rivers. Patterns varied markedly across taxonomic groups. Within trophic groups we detected increases in the abundance of carnivores by 19% and herbivores by 14.8%, while we estimated decomposers have declined by 21.7% in abundance since 2002. We also found heterogeneity in trends across rivers belonging to different typologies based on geological dominance and catchment altitude, with organic lowland rivers having generally higher rates of increase in abundance across taxa and trophic groups, with siliceous lowland rivers having the most declines. Our results reveal a complex picture of change in freshwater macroinvertebrate abundance between taxonomic groups, trophic levels and river typologies. Our analysis helps with identifying priority regions for action on potential environmental stressors where we discover macroinvertebrate abundance declines.     

河流微生境异质性与大型底栖动物空间分布的关系

大型底栖动物是河流生态系统较好的指示类群,越来越广泛地应用于河流生态状况评价.识别大型底栖动物空间分布的影响因素可以分为宏观尺度因子、中观尺度因子和微观尺度因子.前人的研究较多集中于中观尺度.本研究基于10 m河段微生境因子与大型底栖动物调查,采用地统计学方法,在微观尺度上分析了大型底栖动物空间分布特征及其与微生境的关系.结果表明:不同生境类型中底栖动物指标存在差异性,激流、深潭和急流的Shannon指数平均值分别为2、1.9、1.78;大型底栖动物密度、生物量、丰富度指数及Shannon指数具有空间自相关性,存在一定的扩散效应;微生境因子与大型底栖动物指标及物种的空间关系存在差异性,其中,水深和流速与大型底栖动物关系的拟合度较弱,底质组成与大型底栖动物的拟合关系相对较好,底栖动物密度与粒径<4 mm底质体积百分比呈现正空间自相关,生物量、丰富度指数、Shannon指数与粒径>32 mm底质体积百分比呈现正空间自相关.本研究结果可为底栖动物扩散机制研究、调查样方设置、物理生境修复等提供参考.     

城市化下平原河流水系变化及空间响应

针对平原河网地区水系形态难以刻画并且受城市化的空间影响难以定量等问题,以太湖平原杭嘉湖地区为例,基于地形图获取的1980s与2010s水系数据和遥感影像等资料,运用多重分形理论及地理加权回归模型,定量揭示了20世纪80年代以来城市发展对河网水系演变的影响。结果表明：（1）杭嘉湖地区河网密度和水面率均呈减小趋势,衰减率分别为10%、13%;区内水系分布集中,均匀性下降;河流曲度降幅为0.5%,干流面积长度比在中、高城市化区域增幅较大。（2）水系变化对城市化的响应在空间上存在较为明显的异质性。城市化水平越低,水系形态演变越剧烈,空间分布不规则性越明显。（3）杭嘉湖地区存在"低-低"、"低-中"、"低-高"、"中-高"4种不同的城市化水平转变类型。城市化水平未发生转变时,水面率衰减更为剧烈,且水系空间分布均匀性下降,水系形态变化较大;城市化水平转变幅度越大,水系均匀化分布趋势越明显;受政策影响"中-高"发展区域仅河网密度变化较为明显。本研究将为城市河网水系保护和生态环境可持续发展提供科学参考。     

Dominance rank predicts social network position across developmental stages in rhesus monkeys

Social network analysis is increasingly common in studying complex interactions among individuals. Across a range of primates, high-ranking adults are generally more socially connected, which results in better fitness outcomes. However, it still remains unclear whether this relationship between social network position and dominance rank emerges in infancy and whether, in species with a social transmission of dominance rank, social network positions are driven by the presence of the mother. To fill this gap, we first explored whether dominance ranks were related to social network position, measured via eigenvector centrality, in infants, juveniles, and adults in a troop of semi-free-ranging rhesus macaques (Macaca mulatta). We then examined relationships between dominance rank and eigenvector centrality in a peer-only group of yearlings who were reared with their mothers in either a rich, socially complex environment of multigenerational (MG) kin support or a unigenerational group of mothers and their infants from birth through 8 months. In Experiment 1, we found that mother's network position predicted offspring network position and that dominants across all age categories were more central in affiliative networks (social contact, social grooming, and social play). Experiment 2 showed that high-ranking yearlings in a peer-only group were more central only in the social contact network. Moreover, yearlings reared in a socially complex environment of MG kin support were more central. Our findings suggest that the relationship between dominance rank and social network position begins early in life, and that complex early social environments can promote later social competency. Our data add to the growing body of evidence that the presence/absence of the mother and kin influence how dominance rank affects social network position. These findings have important implications for the role of caregivers in the social status of developing primates, which ultimately ties to health and fitness outcomes.     

Ontogenetic structure and distribution patterns of ichthyoplankton in the confluence zone of two river systems in the Eastern Amazon

The ontogenetic structure and longitudinal variability of ichthyoplankton in a confluence zone of two river systems in the Eastern Amazon were evaluated between December 2018 and April 2019, at the time 137 eggs and 7,687 larvae of fish were captured. Ichthyoplankton proved to be heterogeneous between sections of rivers with differences in the number of taxa and abundance. The assemblages were distinguished by a NMDS Analysis, a ANOSIM, a SIMPER and a CCA, they presented a spatial zonation pattern with strong distinction and variability in the composition of the species between the river systems, under strong influence of limnological variables. The assemblages were mainly represented by larvae of Clupeiformes and Perciformes in the clear waters of the Tapajós river and Characiformes and Siluriforms in the cloudy waters of the Amazon river, influenced by the existence of a limnological gradient. Larvae in more advanced development stages were predominant in the Tapajós river while early stages were dominant in the Amazon river. The confluence zone does not seem to be a spawning area, but it is an important transport site for the larvae to reach the nursery areas in the lower stretch of the Amazon river. The encounter of these two river systems seems to guarantee the survival and biological recruitment of several fish species.     

Context dependency in biodiversity patterns of central German stream metacommunities

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Nitrous oxide emissions in the Shanghai river network: implications for the effects of urban sewage and IPCC methodology

Global nitrogen (N) enrichment has resulted in increased nitrous oxide (N₂O) emission that greatly contributes to climate change and stratospheric ozone destruction, but little is known about the N₂O emissions from urban river networks receiving anthropogenic N inputs. We examined N₂O saturation and emission in the Shanghai city river network, covering 6300 km², over 27 months. The overall mean saturation and emission from 87 locations was 770% and 1.91 mg N₂O‐N m^?2 d^?1, respectively. Nitrous oxide (N₂O) saturation did not exhibit a clear seasonality, but the temporal pattern was co‐regulated by both water temperature and N loadings. Rivers draining through urban and suburban areas receiving more sewage N inputs had higher N₂O saturation and emission than those in rural areas. Regression analysis indicated that water ammonium (NH₄⁺) and dissolved oxygen (DO) level had great control on N₂O production and were better predictors of N₂O emission in urban watershed. About 0.29 Gg N₂O‐N yr^?1 N₂O was emitted from the Shanghai river network annually, which was about 131% of IPCC's prediction using default emission values. Given the rapid progress of global urbanization, more study efforts, particularly on nitrification and its N₂O yielding, are needed to better quantify the role of urban rivers in global riverine N₂O emission.     

基于生态网络的山水林田湖草生物多样性保护研究——以广西左右江为例

“山水林田湖草是生命共同体”的理念强调生态系统的整体性,反映了自然界各生态系统之间的联系,表明对生态环境的治理要建立在系统论的思想方法上,怎样将“山水林田湖草”的理论思想落实到具体的地区已成为生态保护与修复的关注热点。生态网络的构建不仅可以连接破碎生境,而且能够综合考虑生态系统的各个要素,因此,以广西左右江流域为例,选取保护区作为生态源地,结合最小累积阻力模型（MCR,minimum cumulative resistance）和整体连通性指数（IIC,integral index of connectivity）,分析潜在生态廊道的结构组成以及源地重要性,探讨研究区潜在生态网络“山水林田湖草”空间分布。研究结果表明：通过构建生态网络识别出69条潜在生态廊道,但在研究区中部没有可利用的廊道,导致明显的南北阻隔;在51个源地斑块中,仅有3个斑块的重要性指数大于0.2,景观整体连通性较低;通过廊道景观构成的分析发现,耕地占廊道面积比例达20.28%,仅次于自然林地（74.16%）,说明耕地对生态网络的构建有重要影响。最后通过廊道与道路的叠加选取9个关键生态节点和23个断裂点,并提出相应的修复和优化对策。研究结果可为广西左右江流域生物多样性保护提供方法和建议,同时作为对“山水林田湖草”生态保护与修复的探索,能够为今后类似研究提供参考。     

Environmental drivers of ant species richness and composition across the Argentine Pampas grassland

Understanding the underlying mechanisms causing diversity patterns is a fundamental objective in ecology and science‐based conservation biology. Energy and environmental‐heterogeneity hypotheses have been suggested to explain spatial changes in ant diversity. However, the relative roles of each one in determining alpha and beta diversity patterns remain elusive. We investigated the main factors driving spatial changes in ant (Hymenoptera, Formicidae) species richness and composition (including turnover and nestedness components) along a 500 km longitudinal gradient in the Pampean region of Argentina. Ants were sampled using pitfall traps in 12 sample sites during the summer. We performed a model selection approach to analyse responses of ant richness and composition dissimilarity to environmental factors. Then, we computed a dissimilarity partitioning of the contributions of spatial turnover and nestedness to total composition dissimilarity. Temporal habitat heterogeneity and temperature were the primary factors explaining spatial patterns of epigean ant species richness across the Pampas. The distance decay in species composition similarity was best accounted by temperature dissimilarity, and turnover had the greatest contribution to the observed beta diversity pattern. Our findings suggest that both energy and environmental‐heterogeneity‐related variables are key factors shaping richness patterns of ants and niche‐based processes instead of neutral processes appear to be regulating species composition of ant assemblages. The major contribution of turnover to the beta diversity pattern indicated that lands for potential reconversion to grassland should represent the complete environmental gradient of the Pampean region, instead of prioritizing a single site with high species richness.     

Heterogeneity and typology of fish habitat in the main stream of a Breton coastal river (Elorn-Finistère,France)

Hydrobiologia - To study the salmonids potential production of a coastal river main stream from simple characterization of the fish habitat, it was necessary to rate the hydrosystem's spatial...     

珠三角河网裸藻的多样性特征

珠三角河网是珠江汇入南海的必经之地,2012年对该水域裸藻门及各属的多样性特征及影响因子进行系统阐析。调查期间共发现裸藻12属84种,其中裸藻属是最主要类群,其次为扁裸藻属和囊裸藻属。珠三角河网独特的地理位置和人类活动造成的水体富营养化是该水域裸藻物种多样性丰富的主要原因。季节特征显示,丰水期裸藻的种类丰富度和生物量均明显高于枯水期。除了洪水引发的裸藻物种的外源供给增大外,泄洪所带来的有机质的增加也是有利因素。此外,丰水期对应的高温也是有益条件。空间特征存在明显的季节差异,丰水期河网外侧站位的生物量和种类丰富度高于中部站位,主要原因是受径流影响较大;枯水季节除广州附近站位的值明显偏高外,其它站位间差异不大,营养盐的空间格局是主要决定因素。尽管裸藻主要依赖于沿江静水水体中的外源供给,分析表明,其在随水流下行的过程中存在增长过程。不同藻属相对组成的结果显示,扁裸藻属和囊裸藻属因属于生长缓慢的K-选择策略型,富集营养物质的能力不及裸藻属,仅在枯水期与裸藻属形成互补优势。裸藻门及主要属的生物量与种类丰富度呈线性正相关关系,偏重于多样性单峰模式的上升区。     

Poly-beta-hydroxy alkanoate and the support of river biofilm metabolism following radical changes in environmental conditions

Endogenous carbon reserves such as poly-beta-hydroxy alkanoate (PHA) can sustain microbial viability during conditions of nutrient deprivation. Microbial extracellular enzyme activities under one set of environmental conditions might be wholly inappropriate for another, and thus PHA might also serve as an energy source as the biofilm acclimates to a changed environment. In order to test this hypothesis, radical changes in environmental conditions were imposed upon river biofilms by transferring them between three rivers of acid, circum-neutral and alkaline pH. The findings supported the hypothesis; each of the transfers resulted in reduced PHA levels, while the physiology of the biofilm (metabolic activity, population density, phosphatase & glucosidase activities) acclimated to the environmental conditions of the recipient site. The greatest PHA depletion was observed when the magnitude of the imposed change resulted in an inability of phosphatase enzyme to respond to the change. The implicit greater dependence on the reserves of PHA, is similarly consistent with the hypothesis.     

平原圩区水系结构与功能特征及其影响机制——以昆山南部为例

明晰平原河网水系结构和功能的影响机制对区域生态可持续发展具有重要意义。以昆山市南部防洪分区为例,选取水系指标分析圩区单元尺度下的水系网络结构与调蓄功能,并构建贝叶斯网络模型,综合考虑用地、自然、工程与政策管理等因子及其相互作用,定量探究水系结构与功能的影响机制。结果表明:(1)水系网络结构具有显著空间异质性,且水系调蓄功能与结构特征密切相关,较复杂的水系形态结构往往表现出较强的调蓄功能;(2)政策、工程、用地和自然条件等因子对水系调蓄功能的影响强度依次减弱;(3)识别水系功能优化目标下的关键变量与关键状态子集,可从社会-生态协同视角指导圩区单元的水系治理与优化。研究结果可为平原圩区水系网络健康与可持续发展提供理论参考和决策依据。     

珠三角河网区典型生境植物群落构成特征及生态修复

如何实现生态文明建设与三生空间高度混杂地区的高质量协同发展是珠三角河网区新时期面对的重要难题。以2018—2021年间积累的第一手田野调查资料为基础,针对广佛地区20处样地202个样点,综合生态学数量分析与风景园林学空间分析方法,研究河网区典型生境的植物群落构成特征及应用。结果表明：(1)珠三角河网区植物物种丰富,维管束植物共122科382属551种;植物群落“乔、灌、草、藤本”垂直结构完整,但乡土植物占比较低、外来入侵较严重;(2)动物友好植物种类丰富,共有鸟类友好植物88种、昆虫类友好植物90种、鱼类两栖类友好植物34种,但缺乏针对动物友好生境的科学配置;(3)河网区包括滨水、坑塘、农田、聚落四类典型生境以及9个稳定的植物群系,但在长期人为干扰下其生态功能和水乡风貌特征被严重削弱。最后,以佛山大美公园为例,探讨了以恢复河网区生物多样性和特色景观风貌为目标的生态修复实践。研究为珠三角河网区地域性景观恢复和三生空间混杂区域的近自然生态修复提供了重要的规划设计蓝本和实践示范。     

Testing the facilitation-competition paradigm under the stress-gradient hypothesis: decoupling multiple stress factors

While the facilitation-competition paradigm under the stress-gradient hypothesis has received recent attention, its rigorous testing is yet to be explored. Most of the studies have considered a switch in the net interactions from competition to facilitation with increasing environmental stress as primary evidence supporting the hypothesis, though few studies examined changes in interaction along a full range of a stress gradient. Here, we have conceptualized possible variations in the patterns of change in interaction strength along such gradient. Based on this, we empirically evaluated the temporal shift in the interaction between two marine sessile animals, goose barnacles (Capitulum mitella) and mussels (Septifer virgatus), under multiple stress factors. The net effect of goose barnacles on mussel survivorship was positively related to the total stress gradient encompassing two stress factors, physical disturbance and thermal stress, while no negative value occurred even under mild conditions. When the two stress factors were treated separately, however, the net effect demonstrated apparently different patterns: monotonic increase with physical disturbance versus a quasi-asymptotic pattern (no change over a wide range) with thermal stress. These variable situations have not previously been recognized in this discipline, and the present study emphasizes the importance of an integrative and mechanistic approach to testing and deciphering the facilitation-competition paradigm.     

A novel approach to assess the impact of landuse activity on chemical and biological parameters in river catchments

1. Natural variation in environmental parameters, as well as practical constraints in study design and sampling methodology, often pose difficulties in treating impact assessments in river catchments as controlled field experiments. It is frequently impossible to develop robust relationships between reference and test stations prior to the onset of an impact and the range of statistical tools which can be adopted in data analysis to detect a change or disturbance is limited. 2. In an attempt to overcome these problems we introduce a novel disturbance index to assess the impact of landuse activities on river systems. The index identifies differences in hydrochemical parameters and macroinvertebrate community metrics between reference and test stations (at a set level of significance). This approach allows for objective assessment of the occurrence and direction of change as well as the duration of an impact. The disturbance index can be applied at different scales – for a single stream, a catchment or a region. 3. In this paper we describe the derivation of the index and illustrate its utility through worked examples. We use the index to assess impact of clearfelling on hydrochemical parameters such as hydrogen ion concentration, total hardness, suspended solids, conductivity and nitrate concentration as well as on macroinvertebrate parameters including abundance, richness, reciprocal of Simpson's diversity index, evenness, Ephemeroptera/Plecoptera/Trichoptera (EPT) richness and percentage of EPT taxa. 4. The sensitivity of the disturbance index changes with scale of application however, and the clearfelling (CF) index has proven sensitive to the detection of even quite small changes, although in these cases ecological significance should be considered. We show that the CF index, particularly when derived from a regional scale, is a conservative index but is very robust to variation in the number of samples used in its derivation. The application of the index corresponded very well with the application of more standard statistical approaches. We believe that the index can thus be applied to other impact studies with similar project design.     

网络理论在入侵生物学中的应用研究现状

生物入侵是一个动态有序的过程,其发生和危害存在异质性,通常由来源地、入侵地和它们之间的连接构成的系统中的自然、生物、社会等因素所决定。网络理论是研究复杂系统的一种新方法,本质是从复杂的信息中抽象出规律、揭示系统的结构特征共性。近20年,网络理论已被应用于生物入侵研究。本研究综述了网络理论在生物入侵研究中的应用进展,明确了主要的研究方向和前沿热点,认为:2000年以来国际上已开展的研究集中在评估外来物种入侵风险和入侵后对生态系统影响2个方面;外来物种随运输网络入侵的风险评估和景观连接性对入侵物种扩散的影响、外来物种入侵对本地物种间互作网络的影响及生态群落可入侵性是网络理论应用的热点;研究热点具有明显的时间发展特征,2013年以前多是对生态系统的影响,近10年来主要是风险评估。我国利用网络理论研究外来物种入侵较少且集中于对生态系统的危害,未来应加强对外来物种的时空定量传入和扩散风险评估,为我国制定和提升外来入侵物种早期监测预警、阻止新的入侵、抑制进一步扩散的管理措施提供依据。