植物顽拗性种子研究进展

对植物顽拗性种子的概念、物种分类、形态、分布及一些生理生态特征进行了综述,分析了顽拗性种子脱水敏感性的原因和对环境的生态适应性,探讨其可能的进化地位和贮存技术。同时,对顽拗性种子研究的发展趋势和应用前景进行了展望,即加强生境调查,更新顽拗性种子植物数据库,从形态学、生理生态学和分子生物学分析种子顽拗性本质。     

Differential Distribution of Metals and Enzymes in Quanzhou Bay Estuarine Wetland Soils under Three Mangrove Species

This study aimed to investigate the effects of three dominant mangrove species (Avicennia marina, Aegiceras corniculatum, and Kandelia obovata) on the distribution of the metal elements Fe, Mn, Cu, and Zn and the enzymes urease, phosphatase, polyphenol oxidase, and catalase. Concentrations of the metallic elements and enzymatic activities were quantified in soils under the three mangrove species in the Quanzhou Bay estuarine wetland, a typical coastal wetland in China. Results showed that A. corniculatum promoted aggregation of Mn, urease, and phosphatase, while K. obovata contributed to accumulation of Cu, urease, and phosphatase. Furthermore, A. marina induced activation of Zn and accumulation of urease, phosphatase, and catalase. The characteristic enzyme and metal distributions induced by the different mangrove species are likely to result from different planting times, root systems, and soil pH and salinity. Moreover, the three mangrove species were found to influence the diversity of elemental and enzymatic stoichiometry through differences in the soil microenvironment, which can promote biodiversity in wetland ecosystems. These findings provide a useful guideline to develop strategies for restoration of estuarine wetlands.     

The Concept of City Carbon Maps: A Case Study of Melbourne,Australia

Cities are thought to be associated with most of humanity's consumption of natural resources and impacts on the environment. Cities not only constitute major centers of economic activity, knowledge, innovation, and governance—they are also said to be linked to approximately 70% to 80% of global carbon dioxide emissions. This makes cities primary agents of change in a resource‐ and carbon‐constraint world. In order to set meaningful targets, design successful policies, and implement effective mitigation strategies, it is important that greenhouse gas (GHG) emissions accounting for cities is accurate, comparable, comprehensive, and complete. Despite recent developments in the standardization of city GHG accounting, there is still a lack of consistent guidelines regarding out‐of‐boundary emissions, thus hampering efforts to identify mitigation priorities and responsibilities. We introduce a new conceptual framework—based on environmental input‐output analysis—that allows for a consistent and complete reconciliation of direct and indirect GHG emissions from a city. The “city carbon map” shows local, regional, national, and global origins and destinations of flows of embodied emissions. We test the carbon map concept by applying it to the greater metropolitan area of Melbourne, Australia. We discuss the results and limitations of the approach in the light of possible mitigation strategies and policies by different urban stakeholders.     

Land use and biodiversity patterns of the herpetofauna: The role of olive groves

The intensification of agriculture has significant environmental consequences. This intensification entails the simplification and homogenisation of the landscape, which leads to strong negative impacts at ecosystem level, including declines in animal biodiversity. The purpose of this study was to assess the effect of different land uses on reptilian and amphibian biodiversity patterns at a regional scale by analysing a large database on the presence of amphibians and reptiles in Andalusia (southern Spain). GIS techniques and the Ecological-Niche Factor Analysis (ENFA) were applied in order to assess whether the habitat was suitable for each reptilian and amphibian species, when the land use variables were excluded. The incongruence between the potential and the observed species richness was then correlated with the main types of land use in Andalusia. Our results showed that irrigated and unirrigated olive groves were associated with a biodiversity deficit of amphibians and reptiles respectively, whereas natural forests and pastures, along with more heterogeneous crops areas, were more suitable. A clustering analysis showed that generalist species were related to olive groves whereas rare and specialist species were related to land uses related to natural vegetation. In summary, our results indicate that large areas covered by olives groves harbour less amphibian and reptilian diversity, thus suggesting that agro-environmental schemes should be carried to promote the species richness in these crops.     

Direct N2O emission factors for synthetic N‐fertilizer and organic residues applied on sugarcane for bioethanol production in Central‐Southern Brazil

The production and use of biofuels have increased rapidly in recent decades. Bioethanol derived from sugarcane has become a promising alternative to fossil fuel for use in automotive vehicles. The ‘savings’ calculated from the carbon footprint of this energy source still generates many questions related to nitrous oxide (N₂O) emissions from sugarcane cultivation. We quantified N₂O emissions from soil covered with different amounts of sugarcane straw and determined the direct N₂O emission factors of nitrogen fertilizers (applied at the planting furrows and in the topdressing) and the by‐products of sugarcane processing (filter cake and vinasse) applied to sugarcane fields. The results showed that the presence of different amounts of sugarcane straw did not change N₂O emissions relative to bare soil (control). N‐fertilizer increased N₂O emissions from the soil, especially when urea was used, both at the planting furrow (plant cane) and during the regrowth process (ratoon cane) in relation to ammonium nitrate. The emission factor for N‐fertilizer was 0.46 ± 0.33%. The field application of filter cake and vinasse favored N₂O emissions from the soil, the emission factor for vinasse was 0.65 ± 0.29%, while filter cake had a lower emission factor of 0.13 ± 0.04%. The experimentally obtained N₂O emission factors associated with sugarcane cultivation, specific to the major sugarcane production region of the Brazil, were lower than those considered by the IPCC. Thus, the results of this study should contribute to bioethanol carbon footprint calculations.     

Establishing an ecological vulnerability assessment indicator system for spatial recognition and management of ecologically vulnerable areas in highly urbanized regions: A case study of Shenzhen,China

The extensive use of modeling and technologies such as a geographic information system (GIS) in ecological vulnerability assessment and the recognition of eco-environmentally vulnerable areas from the perspective of spatial positioning provide important complements to urban ecological space management research. This study establishes an ecological vulnerability assessment indicator system containing nine elements and twelve indicators with respect to ecological sensitivity, ecological pressure, and self-resilience. The range of ecologically vulnerable areas in a highly urbanized region is spatially recognized. Management strategies are proposed with regard to institutionalization and marketization. The results show that the ecological vulnerability in Shenzhen is good overall and that most areas are moderately vulnerable; the goal of space management is to enhance ecological function and prevent further expansion of the city as a threat to ecological security. Highly vulnerable areas are mainly distributed in the west and agglomerate with urban functional areas; it is suggested to delimit an ecological red line in this region and implement the most stringent “steel wire” control following the existing ecological protection law in China. Furthermore, this study proposes an ecological preparedness system suited for the particularity of the highly urbanized region in Shenzhen and attempts to introduce marketization into ecological restoration to solve the economic and social plight of ecological reconstruction in highly urbanized regions. The vulnerability assessment results objectively reflect the condition of the regional ecological environment, and the space management policy has implications for ecological protection, resource utilization, and sustainable development in similar cities.     

Factors influencing cyanobacteria community structure in Chara-lakes

For practical reasons, cyanobacteria attract scientific interest in eutrophicated, often degraded water bodies. Much less attention is paid to blue-greens in less fertilized lakes, including a group of macrophytic lakes with vegetation dominated by charophytes (Chara-lakes). In this study, therefore, two small, mid-forest Chara-lakes with negligible recreational use were compared with two large Chara-lakes subject, along with their drainage basin, to higher human pressure. An attempt was made to find out whether there are any differences in the qualitative and quantitative structure of cyanobacteria and in cyanobacteria functional groups between the studied Chara-lakes. In addition, the lakes ecological status was assessed based on their total phytoplankton and cyanobacteria biomass.Small mid-forest Chara-lakes were distinguished by Chroococcales taxa, while Oscillatoriales and Nostocales preferred large recreationally used water bodies with catchment areas changed by human activity. Aphanothece minutissima, Merismopedia tenuissima, Aphanizomenon gracile, Aphanocapsa holsatica and Cyanodictyon planctonicum differentiated among the studied Chara-lakes.Although cyanobacteria dynamics did not differ Chara-lakes from eutrophic water bodies, the dominance of cyanobacteria was only detected in the two large Chara-lakes characterised by a worse ecological status compared to the small mid-forest ones.Alkalinity, water temperature, colour and, to a lesser extent, TP and TN:TP ratio are postulated to be water properties which, in addition to extensive charophyte meadows, control the development of cyanobacteria in the studied Chara-lakes.     

Fractal dimensions of metropolitan area road networks and the impacts on the urban built environment

The fractal dimension of road networks emerges as a measure of the complexity of road transport infrastructures. In this study, we measured fractal dimensions of both the geometric form (i.e., the layout of the roads) and structure hierarchy (i.e., the connections among roads) of the major road networks in the largest 95 U.S. metro areas. We explained the causes of the variances in these fractal dimensions, especially the one for structure hierarchy. Further, we hypothesized the impacts of these fractal dimensions on the urban built environment and validated our hypotheses using path analysis. We found that a larger geometric fractal dimension (D_g) shows a more uniform distribution of roads over the metro area, which provides the accessibility to suburban areas and incentives to low-density development. A larger structural fractal dimension (D_s) indicates the highly-connected roads (e.g., highways) tend to join to other highly-connected roads so that most roads can be reached by a small number of neighboring roads (i.e., the small-world phenomenon). As D_s increases and the small-world effect become more significant, daily vehicle miles traveled per capita (DVMT/Cap) decline. However, D_s should be kept low in order to reduce the DVMT/Cap as population size increases. We consider that the low D_s can contribute to more mixed, polycentric and more uniform on an urban area-wide basis. Overall, higher D_g and D_s of the major road network in a metro area leads to higher per capita carbon emissions of transport, and lower quality of life as population increases. In the end, we conclude that fractal dimensions can provide valuable insight into the nature of the transportation land use nexus.