The local responses of aquatic ecosystems to adjacent grassland conservation: Can streams of dreams exist in a degraded riverscape?

1. Landscape homogenization and the removal of riparian areas have altered stream ecosystems worldwide. Numerous conservation programmes attempt to improve water quality and increase instream habitat heterogeneity to elicit desired biological responses. However, the effectiveness of many conservation efforts on isolated stream fragments remains unknown, especially in grassland regions.
2. The effects of grassland conservation practices and the re-establishment of riparian corridors in the James River basin, South Dakota (USA) on stream water quality, habitat availability and aquatic macroinvertebrate and fish assemblages were studied in an agriculturally dominated prairie landscape.
3. Grassland conservation efforts may have repaired riparian condition, reduced turbidity and created more diverse instream habitat complexes at conservation sites based on comparisons with paired reference reaches. Reference sites were relatively homogeneous, with prevalent siltation, bank erosion and disturbances to the riparian vegetation. Owing to significant riparian vegetation development, overhanging and aquatic vegetation, benthic detritus and woody materials were significantly more common at conservation reaches.
4. Restoration efforts that assume ‘if you (re-)build it, they will come’ (i.e. the ‘field of dreams’ hypothesis) underestimate other important barriers to biodiversity restoration in dynamic, grassland riverscapes. Although aquatic organisms in grassland ecosystems are adapted to rapidly inhabit available habitats, the development of niche space at conservation reaches did not directly result in colonization by aquatic life.
5. Grassland management actions did not address stream connectivity issues or overcome land use influences elsewhere in the riverscape that may govern the responses of aquatic macroinvertebrates and fish. Stream fragmentation and continuing, damaging land use patterns seemed to exceed the positive effects of restoring isolated stream reaches in these heavily degraded catchments. Catchment-scale management strategies that combine reach-level restoration actions with efforts to improve connectivity are likely to be more successful in degraded riverscapes.

     

Biodiversity value of agricultural drainage ditches: a comparative analysis of the aquatic invertebrate fauna of ditches and small lakes

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基于底栖动物完整性指数的洞庭湖典型断面的水质评价

2010年在枯水期、平水期、丰水期对洞庭湖的7个典型断面进行了大型底栖无脊椎动物采样,共获得底栖动物40种,其中节肢动物16种、软体动物18种,环节动物6种。根据Shannon-Wiener物种多样性指数确定了4个相对清洁的断面和3个污染断面,然后进行23种生物指数的综合评估,结果表明,（甲壳动物＋软体动物）分类单元数、Shannon-Wiener物种多样性指数与Goodnight-Whitley指数3个底栖动物生物指数可以用作辨别洞庭湖典型断面水质的敏感生物指数。通过5、3、1记分法对3种生物指数统一量纲后,获得变化范围为3～15的综合生物指数,运用四分法划分出洞庭湖典型断面水质辨别的生物基准：3～6,差;7～9,一般;10～12,好;13～15,很好。据此对7个断面进行重新记分,获得了洞庭湖典型断面水质的基本分区现状：虞公庙、万子湖、目平湖3个断面的水质良好,而鹿角、坡头、南嘴及东洞庭湖4个断面的水质较差。该水质生物学基准基本适合评价洞庭湖典型断面的水质状况。     

Selective digestion of the peptide and polysaccharide components of synthetic humic acids by the humivorous larva of Pachnoda ephippiata (Coleoptera: Scarabaeidae)

In order to identify the potential nutrient and energy sources of humivorous beetle larvae, we carried out feeding trials with soil supplemented with specifically ¹⁴C-labeled model humic acids synthesized by peroxidase-initiated radical polymerization, using the cetoniid beetle Pachnoda ephippiata (Coleoptera: Scarabaeidae) as a model organism. Ingestion of soil by the larvae significantly increased the mineralization of humic acids labeled in their peptide (HA-*peptide) or polysaccharide components (HA-*peptidoglycan and HA-*chitin), whereas the mineralization of humic acids labeled in the aromatic components (HA-*catechol) did not increase significantly. Mineralization was accompanied by a reduction of residual radiolabel in the acid-soluble fraction and an increase in the humic acid and humin fractions of the fecal pellets. During the gut passage, the residual label in peptide or polysaccharide components was transformed into acid-soluble products, especially in the alkaline midgut. High-performance gel-permeation chromatography demonstrated that the changes in solubility were accompanied by large changes in the molecular weight of the residual material. The amount of radiolabel derived from the peptide and polysaccharide components recovered from the larval body and hemolymph was significantly higher than that derived from the aromatic component, which supports the hypothesis that humivorous beetle larvae selectively digest the peptide and polysaccharide components of humic substances, whereas the aromatic components of humic substances are not an important source of nutrients and energy. This is also the first experimental evidence that also chitin and peptidoglycan, the major structural polymers in fungal and bacterial biomass, can be protected from microbial degradation in soil by a copolymerization with phenols and might contribute substantially to the refractory nitrogen pool in soil organic matter.     

基于大型底栖动物群落生物指数的清河水环境模糊综合评价

为评价不同水期清河流域水环境状态,采用模糊综合评价法以大型底栖动物Shannon-Wiener多样性指数、Margalef丰富度指数、Simpson多样性指数、Pielou均匀度指数、FBI(Family Biotic Index)指数和敏感性指数6个生物指数为评价因子进行水体等级隶属度计算,综合比较得到枯水期和丰水期各点位的水体状态等级。清河流域大型底栖动物群落结构组成及生物指数在枯水期和丰水期之间发生变化,整体表现为丰水期生物物种丰度、多样性、丰富度及敏感性指数大于枯水期,清河及主要支流上游生物多样性及敏感性类群比例较大,下游、乡镇及城区附近的生物类群多样性降低,耐污值高的生物比例增加。模糊综合评价结果表明,枯水期和丰水期水体呈清洁、轻度污染、中度污染的样点比例分别为12.5%、12.5%、75%和18.75%、43.75%、37.5%,清河流域干流及支流上游点位多为清洁和轻度污染,下游点位多呈中度污染状态。     

帽儿山溪流中大型底栖动物的定殖对两种树叶分解速率的影响

利用复合网袋法,对五角槭(Acer mono)和稠李(Prunus padus)两种树叶在帽儿山溪流中的分解速率进行了为期105 d的研究。结果表明:五角槭和稠李树叶在溪流中的分解速率常数(k)分别为0.024和0.030,符合指数衰减模型,均属于快速分解组。定殖在五角槭和稠李树叶上的大型底栖动物种类分别有30种和26种,均以蜉蝣目小蜉属(Ephemerella spp.)为优势种。两种树叶上大型底栖动物的摄食功能群的多度和生物量无显著差异,而5次采样间的差异显著。定殖在五角槭树叶上的直接集食者比例最高(45.9%),其次是捕食者(23.8%)和撕食者(22.4%),最少的为过滤收集者,仅占4.6%;定殖在稠李树叶上直接集食者的比例最高(44.6%),其次是捕食者(26.1%)和撕食者(25.4%),过滤收集者仅占1.8%。说明在帽儿山溪流中,随着溪流增大,撕食者种类减少,直接集食者类群的密度对树叶分解速率具有显著影响。     

The role of pond management for biodiversity conservation in an agricultural landscape

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Relative contribution of small mountain ponds to regional richness of littoral macroinvertebrates and the implications for conservation

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基于大型底栖动物的乌伦古湖水质生物学评价

2006年11月至2007年7月在乌伦古湖设置28个采样点按季度对底栖动物采样。共采到大型底栖动物83种,其中寡毛类14种,水生昆虫58种,软体动物7种,其他类4种。年均密度为1048ind/m2,变幅为70～2480ind/m2;年均生物量为10.76g/m2,变幅为0.48～52.53g/m2。根据底栖动物的观测数据,利用Shannon-wie-ner多样性生物指数(H′)、Goodnight修正指数(GBI)、Margalef丰富度指数(d)、Chandler′s生物记分制(CS)和综合生物污染指数(BI)对乌伦古湖水体环境质量的评价结果显示,乌伦古湖水质整体属于轻度污染。人类活动影响较大的区域如73公里小海子、骆驼脖子、海滨浴场和吉力湖等处样点水质相对较差,处于中污染水平;投放牛羊粪养殖鱼种的吉力湖后泡子则为重度污染水平。利用底栖动物对乌伦古湖水质的生物学评价结果与理化指标评价结果基本一致。     

黄河源典型卵石河床底栖动物的小尺度分布

研究卵石河床上底栖动物的小尺度分布对保护河流生态完整具有重要意义。为了解底栖动物在单个卵石上的分布特征,于2012年7月和2013年6月在黄河源区兰木错曲卵石河床选取6个样点进行底栖动物采样调查,同时对样点环境参数进行监测,对河流水质、底栖动物组成、物种丰富度和卵石表面积进行分析,以揭示底栖动物种数、个体数与卵石表面积的关系,探究大卵石层和卵石夹沙层中的底栖动物群落特征。结果表明,研究河段基本处于自然状态,水质为II类。调查期间共采集底栖动物2门、4纲、9目、16科、28属,在物种组成上,以水生昆虫为主。单个卵石上底栖动物的种数和个体数随着卵石表面积的增加呈幂指数增加,对数函数相关系数R~2分别为0.589、0.655(P0.01)。卵石河床上,卵石夹沙层和大卵石层的物种丰富度(10～13种)差别不大,卵石夹沙层的密度(706～868个/m~2)远高于大卵石层(194～360个/m~2)。大卵石不易随水流运动,更适合附石类底栖动物尤其是毛翅目(Trichoptera)生存,大卵石层毛翅目的物种数(2～5种)和密度(12～87个/m~2)均高于卵石夹沙层(1～2种、1～9个/m~2)。毛翅目对河流生态具有重要意义,大卵石层对维持河流生态健康具有重要作用。