两种边坡生态修复模式土壤肥力与酶活性的变化

[目的]研究不同修复技术处理对边坡土壤酶活性的长期影响,以期为土壤地力培育提供理论依据。[方法]以向家坝水电站工程扰动区代表性的天然次生林以及人工次生林为基础,测定不同坡位以及坡向土壤酶活性,探讨土壤酶活性的变化规律,分析酶活性与其他肥力因子间的相互关系。[结果]不论阴坡还是阳坡,两种林地坡面地形部位(上坡位、中坡位、下坡位),除土壤pH值降低以外,下坡位肥力因子均显著提高1.1倍以上,酶活性水平与肥力因子变化基本一致。除过氧酶活性增长不显著外,磷酸酶活性增长91.67%~116.67%,脲酶活性增长5.3%~30.01%,蔗糖酶活性增长1.38~1.56倍;阴坡各项指标均高于阳坡,除过氧酶以外,都增长显著。相关性分析表明,两种修复技术下,碱性磷酸酶、脲酶、蔗糖酶两两之间的正相关关系均达到极显著水平,但与过氧化氢酶活性之间相关性均不显著。[结论]研究区肥力因子总体上呈现空间分布不均匀,沿着坡体从上至下依次增加,北坡高南坡低的趋势,说明坡位坡向影响着土壤内环境的变化进程,因此对于此类边坡坡顶和阳面的二次修复,适当追肥可以更好地进行地力培育和生态修复。     

Fishing efficiency of competitive largemouth bass tournament anglers has increased since early 21st century

Tournament fishing has risen in popularity over the last half a century. As such, social and financial incentives combined with technological advancements are expected to drive changes in angler's capacity to exploit tournament‐eligible fish stocks, as has been observed in commercial fisheries. The aim of this study was to quantify temporal trends in angler efficiency and their ability to exploit a given fish stock relative to effort in largemouth bass fishing tournaments. A collective analysis across seven Illinois reservoirs comparing change through time in angler catch rates and relative population abundances indicated that angler efficiency has generally improved through time. For the decade from 2005 to 2015, a greater than threefold increase in the efficiency of anglers to exploit a static population of largemouth bass was estimated. Anglers have become more efficient at exploiting populations, which is likely to influence management decisions in the future, particularly in harvest‐orientated fisheries and those reliant upon fishery‐dependent surveys.     

干湿交替条件下土壤磷释放及其与土壤性质的关系

通过四川瀑布沟水电站消落区典型土壤磷释放室内模拟试验,研究淹水及干湿交替条件下消落区土壤性质变化情况以及土壤性质与磷释放之间的关系,以期为预防水库水体富营养化,水库消落区合理利用与科学制定管理对策提供参考。结果表明：淹水能够提高土壤活性氧化铁（Feox）含量,淹水风干后土壤Feox含量降低至淹水前的水平;淹水后Feox变化幅度为：旱地〉水田〉果园,紫色土〉冲积土。土壤磷吸持饱和度（DPS）与无定形铁铝氧化物Alox密切相关;土壤最大吸磷量（Qm）淹水时最高增加至2 758.01 mg/kg,土壤淹水后Qm、土壤最大缓冲容量（MBC）、土壤吸磷指数（PSI）值升高;淹水能够明显提高土壤的磷素缓冲容量、土壤的最大缓冲能力和吸附能力、土壤磷的保持率,其原因也是与淹水后土壤无定形铁铝氧化物含量大幅度增加有关;通过主成分分析,土壤磷释放能力主要与土壤磷水平和土壤吸磷能力有关,且主要指标包括土壤有机质含量（OM）、土壤有效磷含量（Olsen-P）、土壤磷保持率（f）、土壤最大吸磷量（Qm）、土壤活性氧化铁（Feox）、土壤活性氧化铝（Alox）等,说明四川省瀑布沟水电站消落区土壤存在较大的磷释放风险。     

City sanitation and socioeconomics predict rat zoonotic infection across diverse neighbourhoods

Rat‐associated zoonoses transmitted through faeces or urine are of particular concern for public health because environmental exposure in homes and businesses may be frequent and undetected. To identify times and locations with greater public health risks from rats, we investigated whether rat characteristics, environmental features, socioeconomic factors, or season could predict rat infection risk across diverse urban neighbourhoods. In partnership with a pest management company, we sampled rats in 13 community areas along an income gradient in Chicago, a large city where concern about rats has increased in recent years. We collected kidneys for Leptospira spp. testing and colon contents for aerobic bacteria such as Salmonella spp. and Escherichia coli. Of 202 sampled rats, 5% carried Leptospira spp. and 22% carried E. coli. Rats were significantly more likely to carry Leptospira spp. on blocks with more standing water complaints in higher‐income neighbourhoods (OR = 6.74, 95% CI: 1.54–29.39). Rats were significantly more likely to carry E. coli on blocks with more food vendors (OR = 9.94, 2.27–43.50) particularly in low‐income neighbourhoods (OR = 0.26, 0.09–0.82) and in the spring (OR = 15.96, 2.90–88.62). We detected a high diversity of E. coli serovars but none contained major virulence factors. These associations between environmental features related to sanitation and infection risk in rats support transmission through water for Leptospira spp. and faecal–oral transmission for E. coli. We also found opposing relationships between zoonotic infection risk and income for these two pathogens. Thus, our results highlight the importance of sanitation for predicting zoonotic disease risks and including diverse urban areas in pathogen surveillance to mitigate public health risks from rats.     

Fishing for conservation of freshwater tropical fishes in the Anthropocene

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Habitat suitability,coverage by protected areas and population connectivity for the Siamese crocodile Crocodylus siamensis Schneider, 1801

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紫坪铺水利枢纽引水系统取消厂前伸缩节研究

结合紫坪铺水利枢纽工程的实际情况，采用三维有限元方法对该工程发电引水系统取消伸缩节的可行性进行了研究。计算结果表明，主厂房上游永久分缝处以一段垫层管代替常规伸缩节，结构位移和应力完全可以满足使用要求，从而达到了取消伸缩节、节省工程投资的目的。     

Turbine entrainment and passage of potadromous fish through hydropower dams: Developing conceptual frameworks and metrics for moving beyond turbine passage mortality

Potadromous fishes are vulnerable to involuntary entrainment through hydropower turbines. However, turbines can also provide a downstream passage route for potadromous fish. Here, we review evidence for turbine entrainment and passage in potadromous fish, and evaluate the effects of these processes on upstream and downstream populations. We develop conceptual frameworks and metrics to quantify vulnerability to turbine entrainment removals, and to quantify the efficiency of turbines as a downstream passage route. We highlight factors that influence these processes and provide case‐studies demonstrating their applicability. We found that juvenile potadromous fish are being entrained through turbines at rates high enough to impact upstream populations. Given that juvenile passage survival is often high, we argue that turbines provide an important downstream passage route for potadromous fish. We show that entrainment vulnerability is likely a function of interactions between in‐reservoir fish behaviour, habitat configuration and operations and thus not well captured by passage mortality estimates. Similarly, we show that while passage mortality can limit downstream passage efficiency, passage success is also dependent on reservoir and forebay navigation, along with survival and fitness in the downstream river. We advocate for a shift in focus away from estimates of passage mortality and injury, which have previously accounted for the majority of turbine passage research. Instead, we recommend an approach that focusses on quantification of the factors that influence downstream passage efficiency and entrainment vulnerability. Moreover, we highlight the need to better understand the broader scale impacts of these events on upstream and downstream populations.     

Projecting future habitat quality of three midwestern reservoir fishes under warming conditions

Rising temperatures caused by climate change are likely to affect cool‐water and warm‐water fishes differently. Yet, forecasts of anticipated temperature effects on fishes of different thermal guilds are lacking, especially in freshwater ecosystems. Towards this end, we used spatially explicit, growth rate potential (GRP) models to project changes in seasonal habitat quality for a warm‐water piscivore (largemouth bass Micropterus salmoides), a cool‐water piscivore (walleye Sander vitreus) and a hybrid piscivore (saugeye S. vitreus × S. canadensis) in two Midwestern reservoirs. We assessed habitat quality for two periods (early and middle 21st century) under two realistic greenhouse gas emission scenarios (a mid‐century emissions peak and a rapid continuous increase in emissions). Largemouth bass were projected to experience enhanced or slightly reduced habitat during all seasons, and throughout the mid‐21st century. By contrast, walleye habitat was projected to decline with anticipated warming, except during the spring in the smaller of our two study reservoirs and during the fall in the larger of our two study reservoirs. Saugeye habitat was projected to either increase modestly or decline slightly during the spring and fall and declines in habitat quality and quantity that were smaller than those for walleye were identified during summer. Collectively, our findings indicate that climate warming will differentially alter habitat suitability for reservoir piscivores, favouring warm‐water species over cool‐water species. We expect these changes in habitat quality to impact the dynamics of reservoir fish populations to varying degrees necessitating the consideration of climate when making future management decisions.     

Amazon floodplain hydrology and implications for aquatic conservation

1. The amplitude, duration, frequency, and predictability of runoff and inundation of aquatic habitats are key hydrological characteristics linked to aquatic ecosystem functioning and biodiversity, but they are seldom integrated into analyses of Amazon floodplain ecology. Remote sensing approaches, measurements and modelling of floodplain hydrology provide a basis for this integration.
2. Effective legislation to protect floodplains and other wetlands depends on operational definitions that require application of hydrological data.
3. Extent and changes of flooded areas are linked to fish diversity and to presence and growth of flooded forests and floating plants.
4. Dam construction reduces river system connectivity and modifies the flood pulse, with major negative implications for floodplain ecosystems adapted to and dependent on a natural flood regime.
5. Trends and variability in climate plus deforestation are altering the Amazon's hydrological cycle, causing changes in discharge and flooded area with concomitant ecological impacts.