Conservation value of variable connectivity: aquatic invertebrate assemblages of channel and floodplain habitats of a central Australian arid-zone river, Cooper Creek

Rapidly expanding water resource development in arid and semi-arid zones of Australia threatens the flow regime and ecological integrity of the few large dryland rivers and their immense floodplains. Efforts to manage and conserve the surface waters of these rivers are hampered by limited scientific data on the ecology of their flora and fauna and on their responses to the high natural variability of flow regime that typifies dryland rivers. Irregular floods connect channel and floodplain wetlands to differing degrees and for varying periods of time but the ecological significance of this connectivity is poorly understood. On Cooper Creek, a large dryland river in central Australia, we explored the degree to which assemblage composition varied with connectivity and hydrological regime. Shortly after protracted regional flooding, we sampled aquatic macroinvertebrate assemblages from the principal microhabitats in 12 channel and floodplain wetlands. Ephemeral and temporary lakes tended to have fewer taxa than semi-permanent channel or terminal lake habitats. Although hydrological connection had only recently been lost for some wetlands, there was already evidence of divergence in aquatic macroinvertebrate assemblage composition. Disruption of the natural variability in connectivity and hydrological regime by excessive water abstraction or river-flow regulation threatens the ecological integrity and aquatic macroinvertebrate biodiversity of dryland rivers. Preservation of the irregular flow regime and sporadic connectivity underpins conservation of the mosaic of floodplain wetlands that play such a crucial role in the ecosystem functioning of rivers such as Cooper Creek.     

改善生态环境防治长江上游水土流失

长江上游长约４５００ｋｍ,流域面积约１００万ｋｍ＾２。本区域地理条件特征。水力、矿产、动植物和旅游资源部十分丰富,具有巨大的经济发展潜力。近几十来,由于本区域森林植被遭到严重破坏,垦殖率不断增高以及对资源的不合理开发利用,致使长江上游地区生态环境日益恶化,水土流失不断加剧。在长江上游地区自然生态系统遭到严重破坏的同时,也给长江中下游地区带来了巨大的危害,改善长江上游生态环境和防治水土流失,是实现流     

Soil macroinvertebrate fauna of a Mediterranean arid system: Composition and temporal changes in the assemblage

Temporal variability is a key factor to understand the structure of belowground communities. Seasonal and annual variations are especially relevant in unpredictable desert ecosystems, where macroinvertebrates are poorly known, despite constituting an important group of soil organisms. In the present study, we analyse the composition and temporal (seasonal and annual) variations of soil macroinvertebrates in an arid area of southern Spain. During two years, macroinvertebrates were sampled in litter and belowground levels by means of soil cores. Results show that the assemblage was dominated by arthropods, especially Formicidae and Coleoptera. The assemblage differed between litter and belowground levels. In litter, detritivores dominated the community, while belowground fauna showed a similar proportion of detritivores and herbivores and a low percentage of predators. Litter and belowground assemblages showed seasonal variations in richness, abundance, biomass and composition, although variations were more marked in litter than belowground. Patterns of seasonal variation also differed between the two study years for both litter and belowground invertebrates. The seasonal and annual variability of the assemblage has potentially important implications for community dynamics in the study system, since the changes in species composition and trophic structure of soil invertebrate assemblages may affect species interactions and food web dynamics over time. Therefore, integrating temporal variability is likely to be crucial to understand soil community dynamics and food webs, especially in heterogeneous, variable systems as deserts.     

典型工业区河道水与底泥氟污染分布及评价

[目的]评价分析浙江省温州市龙湾工业区永强塘河及中横河干支流河道水与底泥氟污染程度和空间分布特征,确定水氟污染严重河道和污染源,为河道水氟污染治理修复提供科学依据。[方法]在野外实地采样基础上,利用离子选择电极法、单因子污染指数法和相关统计法对河道水和底泥氟含量进行测定,评价氟污染程度并探讨氟污染来源。[结果]永强塘河与中横河主干及支流河道采样断面水氟含量超标率分别达到96%和83.3%,永强塘河中游主干及东、西两侧支流河道采样断面水氟污染达到中度和重度污染等级比例分别为60%,85.7%和80%,中横河经开区河段主干和东侧支流河道水氟污染达到重度等级的采样断面比例依次为80%和75%,河道底泥氟污染全部在轻度及以下等级;71.4%的河道采样断面水氟含量与沿岸不锈钢类企业数量相关系数超过0.9。[结论]以含氟工业废水治理为重点,大力开展永强塘河中游支流河道、中横河经济开区主干及东侧支流河道水氟污染综合整治,可有效改善研究区河道水环境质量。     

Brain AChE activity studies in some fish species collected from a mercury contaminated estuary

In an attempt to investigate the impact of the discharge of Hg contaminated effluent from a chlor-alkali industry into the Rushikulya river estuary, brain AChE activity was measured in three fish species, S. sihama, A. nenga and S. argus, sampled from the contaminated water of the estuary. The residual Hg levels in the brain tissue of the fishes were also determined. The maximum brain residual Hg level, 0.702 ± 0.205 mg kg^?1 ww, was recorded in S. sihama. The inhibition of the AChE activity observed in that species was as much as 26.48% when compared to the normal enzyme activity. The levels of inhibition. observed in the other two fish species, A. nenga and S. argus, were also more than the 10% index level suggested. A significant negative correlation observed between the brain residual Hg levels and the AChE activity levels suggested the use of fish brain AChE measurement as a regular monitoring protocol in assessment of the pollution of aquatic systems by Hg.     

Biotic Effects in Planktonic Crustacean Communities in Acifified Swedish Forest Lakes after Liming

In Sweden, approximately 16 000 of a total of about 85 000 lakes have been acidified due to acidic deposition. Of these about 8000 have been treated with limestone powder in order to detoxify the acidified waters and protect sensitive fauna. The present study was performed in ten lakes in the southern part of the country. The lakes belong to four different catchments and were in different stages of acidification at the time of lime treatment. The composition of the zooplankton and fish communities also differed and three lakes were empty of fish at the beginning of the studies. Quantitative sampling of planktonic crustaceans was performed during the ice free season between 1976–87 in five of the lakes and between 1977–87 in the other five. After treatment the pH increased significantly in all lakes except one. The average number of crustacean taxa found per sampling occasion increased in all lakes. Increases were statistically significant in four of the lakes. In the lakes empty of fish, increased abundances of chaoborids inhibited, by predation, the increase of species richness. Species richness increased after the introduction of fish and the subsequent reduction of the chaoborids. At the end of the study, more taxa were found in the limed study lakes than in non-treated west coast lakes with an alkalinity of 0.04–0.10 meq L^-1. Most species normally occurring in oligotrophic forest lakes were found. It was shown that the water quality after liming made the occurrence of sensitive species possible and that predation from fish and interactions within the zooplankton assemblage were of great importance to the species composition and structure of the zooplankton community.     

Influence of invasive palms on terrestrial arthropod assemblages in desert spring habitat

Invasive plants can eliminate native flora and ultimately have negative indirect effects on fauna and the functional ecology of ecosystems, but understanding of these cascading effects on arthropod assemblages is poor. Desert spring habitats are small, isolated landscape elements that are literal oases for flora and fauna and support high diversity assemblages; invasive palms can colonize desert springs and form monocultures. In an effort to understand effects of these invasive trees on higher terrestrial trophic levels at springs, we contrasted assemblage structure of terrestrial arthropods in native vegetation versus invasive palm habitat. We sampled arthropods in paired palm and native habitat at 10 springs in Death Valley National Park, California, USA, during both spring and fall growing seasons using suction sampling. The invading palms Phoenix dactylifera L. and Washingtonia filifera (Linden ex André) supported a mean of only one-sixth of the arthropod abundance, one-third of the species richness, and half the family richness of native habitat. Almost all orders were less abundant in palms, and most families and species were either absent or virtually absent in palm habitat. Both live and dead palm leaves were depauperate, and season and block effects were minimal. Impacts of these visually striking invasives clearly go beyond monopolization of ground cover, and invading palms appear capable of reshaping the functional ecology of desert springs. If control efforts are undertaken, we recommend complete removal of palms, because killed but standing “ghost palms” and associated thatch persist for many years and will continue to provide poor arthropod habitat and prevent native plant establishment.     

Diadromous fish conservation plans need to consider global warming issues: An approach using biogeographical models

Most of the European diadromous fish species are endangered and listed in the habitats fauna and flora directive, the bern convention and the IUCN Red List. Current conservation plans do not address global warming issues and consider the 1900 distribution range as the reference without taking into account the potential re-distribution of these species under global warming. However, for other taxa, predictive models have been used successfully to relate conservation assessment with the impact of global warming. We investigated the distribution of the various diadromous species regularly encountered in Europe, North Africa and the Middle East at the beginning of the 20th century. For each species, we related the observed distribution to a set of environmental variables describing the prevailing climate in the basins, the physical nature of the basins and reflecting historical events known to have affected freshwater fish distribution. We successfully built twenty-one accurate species-specific models out of twenty-eight during both the calibration and the validation phases. Longitude, a factor we interpret as related to biogeographical history, was selected in all models and temperature was included in fifteen models, in six it was the most explanatory variable. These models allowed us to separate the roles of ecology and history in explaining distribution patterns at species level. Historical events such as glaciations constrained the continental distribution of all diadromous species and six of these were also highly temperature-dependent. Based on these results, we claim that these models can be used to predict the potential distribution under changing climatic conditions and provide two relevant examples (i.e. for Alosa alosa and Pe tromyzon marinus). Predictive models could be useful as a preliminary tool to prepare long-term conservation plans on European, national and regional scales.     

汉江与渭河大洪水滞流沉积物性质对比分析

通过广泛野外考察,在汉江上游和渭河干支流发现多次现代大洪水滞流沉积物(SWD),进行样品采集和粒度成分、磁化率特征对比分析。结果表明:汉江上游与渭河大洪水SWD的磁化率都很低,在(20～60)×10-8 m3/kg之间。这与渭河流域马兰黄土L1的磁化率相当。这也正是那些未受到风化成壤作用影响的新鲜沉积物的基本特征。汉江上游与渭河大洪水SWD粒度成分均以粉沙为主,沙级颗粒含量次之,粘土成分含量最少。它们主要是河流洪水悬移质和跃移质成分在高水位滞流环境当中的沉积物。与渭河相比,汉江上游大洪水SWD粒度成分更粗,沙级颗粒成分含量略多。汉江上游大洪水SWD性质主要是粉沙质亚沙土和沙质粉沙土。渭河大洪水SWD性质则主要是粉沙土、沙质粉沙土和粘土质粉沙土。这是因为汉江上游穿行于秦岭和巴山基岩山地之间,羽毛状分布的支流水系比降大,河流搬运动力强,在暴雨洪水期间,不断地向干流输入粗颗粒泥沙。而渭河流域为黄土高原,河流泥沙主要来源于粉沙质的黄土层和地表土壤。该研究成果对汉江上游和渭河流域防洪减灾和水土流失防治具有重要的科学意义。     

Fluvial development and the sediment regime of the lower Calder,Ribble catchment,northwest England

In the lower reaches of the Calder (Lancashire) tributary of the Ribble catchment (northwest England), five river terraces set into the surrounding glacial terrain have been mapped and their underlying sediments radiocarbon dated. The earliest terrace (T1) reflects sandur-style deposition during deglaciation and it aggraded in a reach cut into glacial diamict and glaciolacustrine muds. Incision below T1 spanned the start of the Holocene, driven by a combination of reduced sediment supply under a stabilising landscape and lower base-levels. T2 had aggraded and was being abandoned by 4000 BC; its formation latterly involving a period of comparative stability in terms of channel migration, perhaps a function of extensive forest cover and sea levels reaching above present day levels. The last 3000 years were marked by substantial changes in the sedimentary regime, with increased and varying sediment supply driving cycles of cut-and-fill and greater lateral channel migration. These changes coincided with the first widespread and substantial reductions in forest cover and a progression towards an agricultural landscape. Between the aggradation of terraces T3 and T4 there was a substantial increase in sediment supply, which is broadly in keeping with the erosion history in the surrounding uplands. This sediment slug appears to have induced a switch from highly sinuous meandering to lower sinuosity channels characterised by lateral scroll-style migration. Late Holocene vegetation changes, particularly woodland removal, driven by anthropogenic land-pressure appear to have rendered the floodplain prone to channel migration and the landscape more susceptible to erosion.     

Rove beetles and ground beetles (Coleoptera: Staphylinidae, Carabidae) as indicators of harvest and regeneration practices in western Canadian foothills forests

Staphylinid beetle assemblages from coniferous foothills forest in west-central Alberta, Canada were studied via pitfall trapping to examine the effects of stand age and possible edge effects. Sites included a chronosequence of stands from 1 to 27 years post-harvest, and four types of mature forest that had not been disturbed by fire for at least 80 years. In all, 19 sites were sampled between 1989 and 1991. A total of 98 species were identified, nine of which are reported for the first time in Alberta. Staphylinids were more abundant in mature forest stands but assemblages were more diverse in regenerating stands. Thirty-four rove beetle species showed significant indicator value for particular stands or groups of stands, including mature forest, young forest, and open ground specialists. After harvesting, the catch rate of many forest species decreased dramatically, and open ground species were more commonly collected. Populations of some forest species remained active on logged sites for one or 2 years before disappearing. As stands regenerated, they were colonized by species characteristic of young stands, but true forest species were found only in older unharvested stands. The beetle assemblages from regenerating stands became more similar to those from mature stands as they aged, but still differed considerably from them 27 years after harvesting. Transects across forest-clearcut edges revealed a significant beetle response to habitat edges. Staphylinids assemblages were compared to the ground beetle (Carabidae) assemblage sampled via the same pitfall trapping regime. Mature forest specialists are threatened by fragmentation and loss of habitat. In order to conserve these beetle assemblages, forest managers should retain adequate patches of older successional stages on working landscapes.     

Buffers,barriers and blankets: The (dis)connectivity of catchment-scale sediment cascades

Catchment configuration and the nature of connectivity within and between landscape compartments affect the operation of sediment cascades and geomorphic responses to disturbance events of differing magnitude and frequency. This paper introduces the concept of landform impediments, termed buffers, barriers and blankets, that impede sediment conveyance by limiting the connectivity between landscape compartments. Buffers restrict sediment delivery to channels, barriers inhibit sediment movement along channels, and blankets drape channel or floodplain surfaces affecting the accessibility of sediment to entrainment. These features operate as a series of switches which turn on/off processes of sediment delivery, determining the effective catchment area at any given time. Using previously documented examples, the role of these features in affecting the operation of sediment cascades in a low relief, passive landscape setting such as the Australian landmass is contrasted to examples from high relief, uplifting settings in New Zealand. The Australian examples are further explored by examining how changes to landscape connectivity brought about by human disturbance since European settlement have impacted upon landscape sensitivity and prospects for river recovery. This approach to analysis of impediments to sediment conveyance is generic and can be applied in any environmental setting.     

Combined effects of habitat modification on trait composition and species nestedness in river invertebrates

Changes in catchment land-use and sedimentation have large ecological effects on rivers, but there is limited transferable understanding of the consequences for river conservation. In the Usk river system (Wales, UK), we assessed whether catchment-scale change in land-use and patch-scale sedimentation (i) affected organisms with specific life-history traits and (ii) resulted in nested assemblages with species-poor sites occupied mostly by sub-sets of organisms from richer sites.Reaches in catchments converted to agriculture had nested species assemblages characterised by greater representation of organisms with small body size, shorter life cycle and effective dispersal capacity. In contrast, richer sites in semi-natural catchments supported taxa with longer life cycles. Patch-scale sedimentation was also accompanied by nested patterns in which depauperate patches supported taxa mostly with shorter life cycles, small size and detrital feeding habits. Sediment-free patches were richer and characterised by larger taxa, poor dispersers and predators. Trait diversity was reduced by habitat modification at both scales.We conclude that habitat modification in this river catchment has led to the systematic drop-out at two different scales of specific groups of organisms with particular trait character. Large-scale agricultural intensification appears to have removed larger, longer-lived invertebrates that probably require stable conditions, and we advocate further studies to appraise whether such organisms are at risk more globally from land-use conversion. This river case study is one of the first to combine nestedness analysis with biological trait assessment and it might help in developing transferable methods to predict the conservation impacts of land-use change.     

Relative efficiency of extensive grazing vs. wild ungulates management for dung beetle conservation in a heterogeneous landscape from Southern Europe (Scarabaeinae, Aphodiinae, Geotrupinae)

The goal of this paper is to evaluate the relative efficiency of two strategies that favour dung beetles conservation (Scarabaeinae, Aphodiinae, Geotrupinae) in Southern Europe: extensive grazing and wild ungulate management. We conducted a study in the French Cévennes national park/UNESCO World Biosphere Reserve where dung beetles are distributed in a dichotomous sheep (grasslands, shrublands) and deer (clearings, shrublands, forests) droppings dominating abroad landscape. Natural sheep droppings and deer lumps dung beetle assemblages have been sampled two consecutive years during spring, summer and autumn in five representative habitats. This sampling of natural assemblages allowed for the estimation of (i) the density of trophic resource in the habitats, (ii) the regional dung beetle fauna and the distribution of species among the habitats and (iii) the density of beetles in natural droppings and the evenness of assemblages. High diversity, high species density in droppings and high evenness were observed in grazed shrubland, whereas fewer species were observed in deer lumps. Our results clearly showed that, while wild ungulates manure is not enough to ensure the conservation of the regional dung beetle species pool, the spatial habitat heterogeneity of grazed shrubland allows the local coexistence of numerous species. Consequently, one may expect that the conservation of European dung beetle fauna, especially Scarabaeinae and several long lifetime species, could be enhanced by extensive grazing.     

A river runs through it: Land-use and the composition of vegetation along a riparian corridor in the Cape Floristic Region, South Africa

Riparian zones are important for the many ecosystem services they supply. In settled areas, the vegetation of such zones is shaped by human land-use; this often creates conditions under which alien plant species thrive. Alien plants have been shown to induce large-scale changes in riparian habitats, and they pose a major threat to the continued provision of key ecosystem services. We used direct gradient analysis to assess correlations between land-use and the composition of vegetation along a riparian river corridor in the highly transformed landscape surrounding Stellenbosch in South Africa’s Western Cape Province. Vegetation plots were sampled along the entire length of the river from headwaters to estuary (ca. 40 km). Plant community composition was analyzed in relation to land-use data collected in the field, and additional land-use variables computed from digital land-cover data. Patterns of plant community structure were found to be directly related to land-use, with measures of cover, richness, and diversity differing significantly among land-use types. Portions of the riparian zone adjacent to agricultural land had the greatest level of alien plant cover, while areas bordered by urban land maintained the highest alien species richness. Areas adjacent to grazing and natural lands showed intermediate and low levels of invasion, respectively. Several native species were found to persist in areas with high abundance and diversity of invasive alien plants, suggesting that they will be valuable focal species for future restoration attempts. Due to the level of human-mediated change in many areas of the riparian zone, restoration to historic conditions over most of the river is not considered feasible. These areas should be recognized as examples of novel ecosystems, and management efforts should focus on restoring or creating desirable ecosystem functions, rather than on achieving assemblages comprising only native species.     

Comparison of Coleoptera assemblages from a recently burned and unburned black spruce forests of northeastern North America

Several insect groups have adapted to fire cycles in boreal forests, and can efficiently use new habitats created by fire. Our study aimed at producing a first characterization of post-fire Coleoptera assemblages of black spruce forests of eastern North America. For two years, we sampled Coleoptera using flight-interception traps in burned stands of contrasting age and structure in a 5097-ha wildfire and in neighbouring unburned mature stands. More than 40 species were exclusively captured in burned stands. Time elapsed since fire and proximity of unburned forests were the most significant parameters affecting Coleoptera assemblages. Stand age and structure had limited effects on assemblage structure; the Scolytid Polygraphus rufipennis Kirby was the only common species to clearly favor older stands. Fire-associated Coleoptera assemblages found in our study area were clearly distinct from those found in similar unburned stands; we should thus be conservative in our management approach concerning recently burned stands.     

Surrogate measures for assessing cryptic faunal biodiversity on macroalgal-dominated subtidal reefs

A major impediment to the identification of priority areas for marine biodiversity conservation is a fundamental lack of information about the distribution of many marine species. Comprehensive species inventories for many areas currently do not exist, and performing detailed taxonomic surveys is often prohibitively expensive and time-consuming. Accordingly, there is a need to develop simple and reliable rapid-assessment techniques for mapping marine biodiversity. One potential approach is to use ‘surrogates’ that function as proxies for the distribution of other, less easily sampled, ‘cryptic’ biota. Two potential surrogates for predicting arthropod faunal biodiversity on rock subtidal reefs were investigated in this study: (1) macroalgae, and (2) faunal subsets derived by aggregating the arthropod fauna at higher taxonomic levels. Faunal and macroalgal assemblage composition was only weakly correlated across sites reflecting broad faunal responses to changes in algal structural complexity and/or common environmental gradients. This suggests that algal species composition may not be very informative in mapping patterns of faunal species distribution on reefs. Instead, the best surrogates were related (i.e. nested), subsets of the faunal assemblages such as family-level taxon richness which was found to be a good predictor of arthropod species richness at independent test sites.     

Complementarity among sampling methods for harvestman assemblages

Tropical arthropod surveys generally use a combination of complementary sampling methods to increase the detection of species and individuals, and to decrease the number of singletons. However, given the high arthropod abundance and the taxonomic challenges of arthropod surveys, the combination of different sampling methods may be inefficient and may increase survey costs. Harvestmen were sampled using beating tray, nocturnal search, leaf-litter manual sorting and Winkler apparatus in 70 plots distributed in two areas in Central Amazonia. Every sampled method documented different assemblages, and only the nocturnal search method proved to be efficient in representing both harvestmen richness and composition. Given the data collected from leaf-litter manual sorting, Winkler apparatus and beating tray can be used in inventories to increase the number of species collected, but may be less useful for applied or monitoring studies. Although pooling data from three methods was effective to obtain an overview of species richness, it may not be the more efficient strategy for studies of assemblage associations with environmental variables. As each method may sample distinct assemblages that have different responses to the surrounding environment, pooling data from these different methods may obfuscate patterns of assemblage composition related to environmental factors instead of clarifying them.