生态公共服务视野下城市森林生态-经济系统的协同机理研究

在生态公共服务视野下,尽管当前我国的城市森林发展较为迅速,但对其森林生态经济系统的协同机理研究仍然还是一个新课题。本文结合海南国际旅游岛建设的相关实践,从治理机制、市场机制、利益分配机制、合作机制、扶持机制5个方面,对海南城市森林进行研究,以促进海南城市森林资源的优化利用和社会经济的可持续发展。     

Assessing the utility of topographic variables in predicting structural complexity of tree stands in a reforested urban landscape

The transformation of natural landscapes into impervious built-up surfaces through urbanization is known to significantly interfere with the ecological integrity of urban landscapes and accelerate climate change and associated impacts. Although urban reforestation is widely recognised as an ideal mitigation practice against these impacts, it often has to compete with other lucrative land uses within an urban area. The often limited urban space provided for reforestation therefore necessitates the optimization of the ecological benefits, which demands spatially explicit information. The recent proliferation of tree stands structural complexity (SSC) and topographic data offer great potential for determining the ecological performance of reforested areas across an urban landscape. This study explores the potential of using topographic datasets to predict SSC in a reforested urban landscape and ranks the value of these topographic variables in determining SSC. Tree structural data from a reforested urban area was collected and fed into a tree stand structural complexity index, which was used to indicate ecological performance. Topographic variables (Topographic Wetness Index, slope, Area Solar Radiation and elevation)- were derived from a Digital Elevation Model (DEM) and used to predict SSC using the Partial Least Squares (PLS) regression technique. Results show that SSC varied significantly between the topographic variables. Results also show that the topographic variables could be used to reliably predict SSC. As expected, the Topographic Wetness Index and slope were the most important topographic determinants of SSC while elevation was the least valuable. These results provide valuable spatially explicit information about the ecological performance of the reforested areas within an urban landscape. Specifically, the study demonstrates the value of topographic data as aids to urban reforestation planning.     

Does full protection count for the maintenance of β‐diversity patterns in marine communities? Evidence from Mediterranean fish assemblages

1. Although it is widely recognized that protection may enhance size, abundance, and diversity of fish, its effect on spatial heterogeneity of fish assemblages and species turnover is still poorly understood.
2. Here the effect of full protection within a Mediterranean marine protected area on β‐diversity patterns of fish assemblages along a depth gradient comparing a no‐take zone with multiple unprotected areas is explored. The no‐take zone showed significantly higher synecological parameters, higher β‐diversity among depths, and lower small‐scale heterogeneity of fish assemblages relative to unprotected areas.
3. Such patterns might likely depend on the high level of fishing pressure outside the no‐take zone, as also abundance‐biomass curves seemed to indicate. Results suggested that full protection could play a role in maintaining high β‐diversity, thus reducing the fragility of marine communities and ecosystems, and spatial heterogeneity may represent a reliable predictor of how management actions could provide insurance against undesirable phase shifts.

     

基于PSR模型的黄河陕西段鱼类增殖放流生态安全评价

基于压力、状态、响应模型(PSR)和层次分析法(AHP),确定17项指标通过数据的标准化处理,指标权重赋值、权重一致性检验、评价等级确定以及评价模型的构建,用生态安全评价黄河陕西段鱼类增殖放流效果,分析生态安全所面临的主要问题。结果表明:黄河陕西段2013年增殖放流生态安全度(ESI)评价等级为Ⅱ级,为良好状态;2014年评价等级为Ⅲ级,处于一般状态;2015年评价等级为Ⅳ级,处于较差状态,属于临界不安全状态以下水平。生态安全形势呈现出逐年下降局势。不安全状态受到影响较大的前3个指标是:黄河径流量变化影响、重要生境保持率和公众资源环境保护意识的影响,3个指标下降值占到下降ESI值的64.93%。其次还受到污水排放达标率、鱼类增殖放流量、政策和管理水平、鱼类生物多样性指数、保护区建设、水质综合污染指数、群落结构等诸多因素影响。研究显示,现阶段增殖放流对黄河生态安全有一定影响,还存在一定提升空间。     

Growth and yield responses of upland NERICAs to variable water management under field conditions

This study aimed to investigate the possible causes for inconsistent performances of upland New Rice for Africa (NERICA) varieties in uplands and lowlands, while identifying important determinants in grain yield under deficient soil moisture. We compared the growth and yield of NERICA 1 and NERICA 5 to those of Yumenohatamochi, a Japanese upland variety, and Hinohikari, a Japanese lowland variety, subjected to different water management regimes (continually flooded, supplementary irrigation, and non-irrigation). Under conditions of deficient soil moisture, panicle number per square meter, spikelet number per panicle, and 1000-grain weight of NERICAs decreased, whereas the panicle number of the Japanese varieties experienced little change. In contrast, the grain filling ratio was unaffected by water management, irrespective of variety. The primary source of yield reduction under low soil water conditions was a decrease in spikelet number per panicle, and water stress intensity was the primary factor for the degree of this reduction. Variation in the abortion of secondary rachis-branches caused differences between NERICAs in their spikelet number response to soil moisture deficiency. The inconsistency in NERICA performance across uplands vs. lowlands can be partially attributed to variation in yield response to low soil water conditions. Moreover, water stress intensity and the presence of a water gradient along the vertical soil profile may combine to affect the fluctuation in NERICA performance under upland conditions.     

Coexisting invasive gobies reveal no evidence for temporal and trophic niche differentiation in the sublittoral habitat of Lake Erhai,China

Niche differentiation facilitates the coexistence of species within a community through avoidance of competition via mechanisms involving spatial, temporal and/or trophic dimensions. Where invasive species coexist in their non‐native range, niche differentiation could allow their persistence at higher levels of abundance. Here, we tested whether there was temporal and/or trophic niche differentiation between two congeneric invasive goby species (Rhinogobius cliffordpopei and Rhinogobius giurinus) in the sublittoral habitat of Lake Erhai (south‐west China) through quantifying their diel and seasonal rhythm of locomotion activities, feeding activities and diet composition. Both species displayed two similar diel peaks in activity and two main feeding periods (6:00–10:00 and 18:00–22:00), with rhythms of locomotion and feeding activity not differing significantly between the species in each season. Their diets had a high degree of overlap, being primarily composed of macrozooplankton, aquatic insects and shrimp larvae, with no diel changes across the seasons. Thus, in this habitat, there was no clear temporal or trophic niche differentiation between the invasive congeners, indicating their coexistence with high temporal and trophic overlap. In conjunction with data from the littoral and profundal habitats, the gobies revealed different strategies across the habitats (e.g. spatial segregation, trophic niche differentiation) that minimised their competitive interactions and promoted their coexistence. This suggests that the interactions of invasive fishes during the integration into native communities can be context dependent, varying according to factors including habitat and the availability of food resources.     

Long‐term habitat loss in a lightly‐disturbed population of the Indo‐Pacific humpback dolphin,Sousa chinensis

1. Coastal and estuarine waters are important ecosystems with high primary and secondary productivity, but they are prone to the impacts of habitat loss caused by anthropogenic activities. For species exclusively inhabiting coastal and estuarine waters, such as the Indo‐Pacific humpback dolphin, Sousa chinensis , irreversible habitat loss can have dramatic implications for population viability.
2. A Landsat image database was used to determine the extent of coastal changes along the northern Beibu Gulf, where a large humpback dolphin population is found. The results were compared with the standardized sighting gradient (SPUF) determined from a questionnaire survey of fishermen and likely core habitats identified by application of a global digital elevation model.
3. Both SPUF and likely core habitat results indicated a continuous distribution of the humpback dolphin along the northern Beibu Gulf. Landsat images revealed that 129.6 km² of coastal waters were permanently lost in the past 40 years, 60 km² within the likely core habitats. Although this may be considered small, the impact of such habitat loss could be substantial in some local habitats.
4. The humpback dolphin population in the northern Beibu Gulf should be regarded as one management unit, with two or more social subunits. Immediate systematic surveys are needed to fill information gaps on true distribution range and habitat‐use patterns.
5. Habitat protection actions for dolphins in the northern Beibu Gulf should include both core and linking habitats, including enacting protected areas in core habitats, mitigating anthropogenic impacts in likely habitats, restoring both coastal waters and surrounding landscape quality, effective treatment of industrial sewage discharge, and comprehensive environmental impact assessments for the planning of coastal development projects.

     

Reproductive resilience: a paradigm shift in understanding spawner‐recruit systems in exploited marine fish

A close relationship between adult abundance and stock productivity may not exist for many marine fish stocks, resulting in concern that the management goal of maximum sustainable yield is either inefficient or risky. Although reproductive success is tightly coupled with adult abundance and fecundity in many terrestrial animals, in exploited marine fish where and when fish spawn and consequent dispersal dynamics may have a greater impact. Here, we propose an eco‐evolutionary perspective, reproductive resilience, to understand connectivity and productivity in marine fish. Reproductive resilience is the capacity of a population to maintain the reproductive success needed to result in long‐term population stability despite disturbances. A stock's reproductive resilience is driven by the underlying traits in its spawner‐recruit system, selected for over evolutionary timescales, and the ecological context within which it is operating. Spawner‐recruit systems are species specific, have both density‐dependent and fitness feedback loops and are made up of fixed, behavioural and ecologically variable traits. They operate over multiple temporal, spatial and biological scales, with trait diversity affecting reproductive resilience at both the population and individual (i.e. portfolio) scales. Models of spawner‐recruit systems fall within three categories: (i) two‐dimensional models (i.e. spawner and recruit); (ii) process‐based biophysical dispersal models which integrate physical and environmental processes into understanding recruitment; and (iii) complex spatially explicit integrated life cycle models. We review these models and their underlying assumptions about reproductive success vs. our emerging mechanistic understanding. We conclude with practical guidelines for integrating reproductive resilience into assessments of population connectivity and stock productivity.     

Elasmobranch fisheries in the Arabian Seas Region: Characteristics,trade and management

The Arabian Seas Region plays an important role in the global landings and trade of sharks and rays. The United Arab Emirates (UAE) and Yemen, two countries with stark socio‐economic differences, serve as major regional trade hubs for shark and ray products and four countries (Oman, Pakistan, UAE and Yemen) supply nearly 11% of dried fin exports to Hong Kong. Yet, little information is available on the characteristics of this trade and the fisheries contributing to it. Here, we review the fisheries characteristics, trade, utilization and distribution chain of sharks and rays in 15 countries of the Arabian Seas Region based on published and grey literature, landing surveys, field observations and interviews with fishermen and traders. Although regional shark fisheries remain mostly artisanal, reported shark and ray landings represent 28% of the regional total fish production, reaching 56,074 mt in 2012 (7.3% of total world catches), with Iran, Oman, Pakistan and Yemen ranking as the primary catchers. Utilization and distribution patterns are complex, vary between landing sites and countries, and remain unmonitored. Based on widespread over‐exploitation of most teleost fisheries, current exploitation levels for most sharks and rays are potentially unsustainable. The situation is exacerbated by limited research and political will to support policy development, the incomplete nature of fisheries data, as well as insufficient regulations and enforcement. A better understanding of shark and ray fisheries will be key for regulating trade, promoting conservation and developing management initiatives to secure food security, livelihoods and biodiversity conservation in the region.