凌源至建昌高速公路选线要点浅析

凌源至建昌高速公路位于辽宁省西部,地形、地质、水文等条件复杂。针对凌建高速公路选线的影响因素,列举了各种不利条件下的处理措施,为我省后期山区高速公路选线提供实例经验。

Henry's Law constant for phosphine in seawater:determination and assessment of influencing factors

The Henry＇s Law constant （k） for phosphine in seawater was determined by multiple phase equilibration combined with headspace gas chromatography. The effects of pH, temperature, and salinity on k were studied. The k value for phosphine in natural seawater was 6.415 at room temperature （approximately 23℃）. This value increases with increases in temperature and salinity, but no obvious change was observed at different pH levels. At the same temperature, there was no significant difference between the k for phosphine in natural seawater and that in artificial seawater. This implies that temperature and salinity are major determining factors for k in marine environment. Double linear regression with Henry＇s Law constants for phosphine as a function of temperature and salinity confirmed our observations. These results provide a basis for the measurement of trace phosphine concentrations in seawater, and will be helpful for future research on the status of phosphine in the oceanic biogeochemical cycle of phosphorus.

Advantages of Maize-Legume Intercropping Systems

An experiment was conducted during Kharif seasons of 2009 and 2010 on sandy loam soil of West Bengal, India to evaluate the productivity and economic viability of maize ＋ legume intercropping systems in additive as well as in replacement series with different row proportions. Maize （Zea rnays L.） cv. ＂Vijay＂ （composite）, green gram （Vigna radiata L.） cv. ＂Samrat＂, black gram （Vigna mungo L.） cv. ＂Sarada＂, soybean （Glycine max L. Merril） cv. ＂PK 327＂ and peanut （Arachis hypogaea L.） cv. ＂JL 24＂, were tested in monoculture as well as in intercropping situations with 1：1 （additive series） and 1：2 ratios （replacement series）. The result indicated that intercropped legumes improved the yield components of maize and offered some bonus yield. The highest maize grain yield （2,916.28 kg/ha） and maize equivalent yield （4,831.45 kg/ha） were recorded with maize ＋ green gram （1：1） and maize ＋ peanut （1：I）, respectively. The values of all the competition functions were always greater than unity and maize ＋ black gram （1：2） recorded the highest values of land equivalent ratio （1.433）, area time equivalent ratio （1.374） and land equivalent coefficient （0.421）. Maximum monetary advantage （Rs. 10,579.13） was found with maize ＋ green gam （l：1）. Maize ＋ peanut （1：2） combination recorded the highest relative net return （2.01）, net return （Rs. 28,523.08）, benefit-cost ratio （2.76） ad per day return （Rs. 259.30）.

Sap Flow of Abies georgei var. smithii and Its Relationship with the Environment Factors in the Tibetan Subalpine Region, China

Abies georgei var. smithii is a dominant species playing an important role in protecting biodiversity and sustaining the forestry ecosystems in Southeastern Tibetan Plateau. Stem sap flows of five different diameters at the breast height(DBH) A. georgei var. smithii samples were monitored continuously with the thermal dissipation probe for the entire growing period in order to understand the water transportation mechanism and the effects of environmental factors on its transpiration and growth. Relative environment factors, temperature and humidity of air, photosynthetically active radiation, rainfall, and wind speed, soil moisture, etc. were measured by the automatic weather stations. Diurnal and seasonal variations in sap flow rate with the different stem diameters and their correlations with meteorological factors were analyzed. The diurnal change in sap flow velocity showed a single-peak curve at the daily time scale, whereas a lower sap flow velocity can be observed in the largest DBH sample tree at night. The maximum average velocity was observed in August, whereas the minimum velocity was observed in January, and a large amount of water evaporated in summer owing to the higher sap flow velocity. In addition, sap flow velocity was closely related to changes in the micrometeorological factors, with average sap flow velocity showing significant linear correlations with air temperature, photosynthetically active radiation, rainfall, and vapor pressure deficit of air and soil moisture. Therefore, some measures, improving the light and temperature conditions, should be taken for protecting A. georgei var. smithii population in the Tibetan Plateau.

Aquatic molluscs in high mountain lakes of the Eastern Alps (Austria): Species-environment relationships and specific colonization behaviour

Mountain lakes represent essential stages for aquatic species on their way colonizing habitats of more elevated regions. Despite extensive biological and chemical study, only little has been reported about the species number and density of freshwater molluscs in these waters. The article presented here elucidates the dispersal of aquatic gastropods and bivalves in 12 mountain lakes that are commonly situated in the Eastern Alps, Austria. Molluscs were recorded at 120 sample points, where a total of 13 species （8 gastropods and 5 bivalves） could be determined. Species distribution data as well as results from contemporarily conducted physico-chemical factor recording were subject to weighted average analysis. In addition, a global marginality coefficient indicating the particularity of a habitat inhabited by a focal species as well as a global tolerance coefficient expressing the width of a niche occupied by this species were computed. Species-environment relationships exhibited that species number and specific density decrease with increasing geographic altitude, declining water temperature, and decreasing amount of submerged vegetation. Whilst waters of the montane altitude level are partly charcterized by high number of mollusc species （〉 10）, lakes of the subalpine altitude level commonly bear 1 or 2 species with 〈〈1 ind./mz. As proposed by the results of statistics, 9 of the 13 mollusc species are characterized by a pronounced behaviour as specialists with respect to most environmental factors. The four remaining species, Pisidium casertanum, Galba truncatula, Radix labiata, and Radix balthica, act as generalists which increases their pioneering role in the long-term occupation of the Central-alpine region.

Withdrawing from Agrarian Livelihoods: Environmental Migration in Nepal

Although about two-thirds of Nepalese families depend on agriculture as their major source of income, the agriculture is mostly rain-fed and it has been adversely affected by water hazards and the subsequent degradation of resources. Based on case studies from three different geographical regions in Nepal, this research examines how environmental factors cause decreasing crop production and push people to abandon agriculture and accept emigration for employment. The research findings suggest a chain of push factors starting from drought or erratic rainfall causing water hazards, which impacts on depletion of crops and livestock, losses in income and employment and increased human mobility and emigration. The paper argues that the Government of Nepal and development partners can be more effective in enabling agrarian families to cope with the water hazards and shocks by formulating pro-poor mitigation and adaptation policies and strategies,focusing both on ‘rapid-onset' and ‘slow-onset' water hazards.

Reproductive Strategies of a Terrestrial Snail along an Altitudinal Gradient on an Oceanic Island

This study reports how the reproductive cycle of a land snail endemic from an oceanic island is shaped by abiotic factors over an altitudinal gradient of 800 m. In addition, the validity of two morphometric shell parameters （maximum diameter and total height） was assessed, as maturation diagnostic characteristics. The authors＇ findings suggest that, at Piedade （200 m）, individuals are active and mature from October/November to March, and they exhibit dormancy in the remaining months, as a consequence of soil dryness. Thus, at low altitude, gonadal maturation was considered to be primarily influenced by photoperiod, rainfall and temperature At Cabeqo da Bola （1000 m）, in turn, individuals are mature from March to July/August and they seem to have minimal gametogenic conditions throughout the remaining months of the year to reproduce. As soil moisture is never a limiting factor, gonadal maturation is mainly shaped by photoperiod and temperature at high altitude. The morphometric shell parameters under analysis were unable to diagnose gonadal maturation, as recently described for related Azorean species.

Biogeography and Evolutionary Factors Determine Genetic Differentiation of Pinus mugo(Turra) in the Tatra Mountains(Central Europe)

Inter Simple Sequence Repeats （ISSR） markers were used to assess genetic diversity within and among populations of dwarf mountain pine （Pinus rnugo Turra） growing in the Tatra National Park （UNESCO Biosphere Reserve） in Southern Poland （Central Europe）. The analyzed population belongs to two different geobotanical sub-districts： the Western and High Tatras. The level of genetic diversity assessed in this study for P. mugo is generally comparable to that reported for the other pine species in the Pinaceae family assessed by ISSR markers, especially with respect to Nei＇s genetic diversity and the percentage of polymorphic bands. Bayesian analysis clustered the analyzed populations into two groups, corresponding to their geobotanical locations in the Tatras. Significant divergence between the two genetical clusters was supported by the results of Analysis of Molecular Variance （AMOVA）. According to the Mantel test, there was no correlation between the genetic distance and the geographical distance. The present study confirms the existence of two genetically distinct dusters of P. mugo populations in the Tatra Mountains. The observed high population-genetic differentiation of P.mugo in the Tatras could be attributed to several genetic, environmental and historical factors occurring in this mountain area.

Road-Spine versus Road-Tube： Roads as Space Generators

Arteries devoted to sustain streams of users, resources and debris, are a foremost factor and pre-condition of the development of urban areas and of the transformation of landscapes. Roadscapes reflect outcomes related to super urbanization tendencies. Often conceived as isolated tubes, roads cut and obscure form, structure, biotic and abiotic factors of sites, urban fabrics and spaces. A broad vision of landscape is a basis for reconceiving roads. The concept of road-spine emerges： the road is conceived as the basis of a bundle of routes, nodes, surfaces, poles and tiles, devised to frame and shape a mosaic of open spaces, crops, farms, stores, basins and service areas. The road-spine entails the idea of a permeable infrastructure devised to integrate diverse functions： from serving various forms of motion, by ordering an isotropic grid of routes, to framing a porous urbanscape; from disposing surfaces meant to preserve biocenosis and biotopes, to favoring osmosis amid land uses. It also prefigures a distribution of land uses dependent on site vocations, and a mosaic of scenarios open to encounter, evasion, rest, amusement, participation, and to spontaneous practices of space.

Soil CO_2 Flux in Different Types of Forests Under a Subtropical Microclimatic Environment

The flux of carbon dioxide （CO2） from soil surface presents an important component of carbon （C） cycle in terrestrial ecosystems and is controlled by a number of biotic and abiotic factors. In order to better understand characteristics of soil CO2 flux （FCO2） in subtropical forests, soil FCO2 rates were quantified in five adjacent forest types （camphor tree forest, Masson pine forest, mixed camphor tree and Masson pine forest, Chinese sweet gum forest, and slash pine forest） at the Tianjiling National Park in Changsha, Hunan Province, in subtropical China, from January to December 2010. The influences of soil temperature （Tsoil）, volumetric soil water content （0soiI）, soil pH, soil organic carbon （SOC） and soil C/nitrogen （N） ratio on soil FCO2 rates were also investigated. The annual mean soil FCO2 rate varied with the forest types. The soil FCO2 rate was the highest in the camphor tree forest （3.53 ± 0.51 μmol m-2 s-I）, followed by, in order, the mixed, Masson pine, Chinese sweet gum, and slash pine forests （1.53 ± 0.25 μmol m-2 sl）. Soil FCO2 rates from the five forest types followed a similar seasonal pattern with the maximum values occurring in summer （July and August） and the minimum values during winter （December and January）. Soil FCO2 rates were correlated to Tsoil and 0soil, but the relationships were only significant for Tsoil. No correlations were found between soil FCO2 rates and other selected soil properties, such as soil pH, SOC, and C/N ratio, in the examined forest types. Our results indicated that soil FCO2 rates were much higher in the evergreen broadleaved forest than coniferous forest under the same microclimatic environment in the study region.

Fungal Community-Plant Litter Decomposition Relationships Along a Climate Gradient

The decomposition of plant litter is a major process of equivalent status to primary production in ecosystem functioning.The spatiotemporal changes in the composition and dynamics of litter fungal community along a climate gradient ranging from arid desert to humid-Mediterranean regions in Israel was examined using wheat straw litter bags placed at four selected sites along the climate gradient,arid,semi-arid,Mediterranean,and humid-Mediterranean sites.Litter samples were collected over a two-year decomposition period to evaluate litter weight loss,moisture,C:N ratio,fungal composition,and isolate density.The litter decomposition rate was found to be the highest during the first year of the study at the Mediterranean and arid sites.Although the Shannon-Wiener index values of the fungal communities in the litter samples were the highest at the humid-Mediterranean site,the number of fungal species was not significantly different between the four study sites.Different fungal groups were found to be related to different study sites:Basidiomycota,Mucoromycotina,and teleomorphic Ascomycota were associated with the humid-Mediterranean site,while Coelomycetes were mostly affected by the arid site.Our results indicate that climate factors play an important role in determining the structure of saprotrophic fungal communities in the decomposing litter and in mediating plant litter decomposition processes.

Understorey plant community assemblage of Australian Eucalyptus woodlands under elevated CO_(2)is modulated by water and phosphorus availability

Aims Given the key functional role of understorey plant communities and the substantial extent of forest cover at the global scale,investigating understorey community responses to elevated CO_(2)(eCO_(2))concentrations,and the role of soil resources in these responses,is important for understanding the ecosystem-level consequences of rising CO_(2)concentrations for forest ecosystems.Here,we evaluated how experimentally manipulating the availabilities of the two most limiting resources in an extremely phosphorus-limited eucalypt woodland in eastern Australia(i.e.water and phosphorus)can modulate the response of the understorey community to eCO_(2)in terms of germination,phenology,cover,community composition and leaf traits.Methods We collected soil containing native soil seed bank to grow experimental understorey plant communities under glasshouse conditions.Important Findings Phosphorus addition increased total plant cover,particularly during the first 4 weeks of growth and under high water conditions,a response driven by the graminoid component of the plant community.However,the treatment differences diminished as the experiment progressed,with all treatments converging at〜80%lant cover after〜11 weeks.In contrast,plant cover was not affected by eCO_(2).Multivariate analyses reflected temporal changes in the composition of plant communities,from pots where bare soil was dominant to high-cover pots dominated by a diverse community.However,both phosphorus addition and the interaction between water availability and CO_(2)affected the temporal trajectory of the plant community during the experiment.eCO_(2)also increased community-level specific leaf area,suggesting that functional adaptation of plant communities to CO_(2)may precede the onset of compositional responses.Given that the response of our seed bank-derived understorey community to CO_(2)developed over time and was mediated by interactions with phosphorus and water availability,our results suggest a limited role of eCO_(2)in shaping plant communities in water-limited systems,particularly where low soil nutrient availability constrains productivity responses.