Spatial evaluation of the ecological importance based on GIS for environmental management: A case study in Xingguo county of China

How to assort with the relationship between the urban construction and the maintenance of ecological security is a hot issue during the process of urbanization. The purpose of this study is to identify the key ecological land maintaining ecological security and to put forward some measures for environmental management. Based on the GIS technology, from the view of water security, biodiversity conservation, disaster protection, natural recreation security, and human disturbance, an integrated index is put forward to evaluate the ecological importance of regional space. Then, a GIS-based approach for evaluating ecological importance was created, with Xingguo county of China as a case study. The results show that the area of core eco-space in the study area accounts for 30% of the total area. These areas mainly consist of the core areas of regional river systems, wetlands, nature reserves, forest parks, and scenic spots and the endangered and protected zone of geological hazards. According to the spatial characteristics of ecological importance for different regions, this study proposes some zoning regulations and measures for environmental management.     

Floristic turnover in Iceland from 15 to 6 Ma – extracting biogeographical signals from fossil floral assemblages

Aim This study aims to document the floristic changes that occurred in Iceland between 15 and 6 Ma and to establish the dispersal mechanisms for the plant taxa encountered. Using changing patterns of dispersal, two factors controlling floristic changes are tested. Possible factors are (1) climate change, and (2) the changing biogeography of Iceland over the time interval studied; that is, the presence or absence of a Miocene North Atlantic Land Bridge. Location The North Atlantic. Methods Species lists of fossil plants from Iceland in the time period 15 to 6 Ma were compiled using published data and new data. Closest living analogues were used to establish dispersal properties for the fossil taxa. Dispersal mechanisms of fossil plants were then used to reconstruct how Iceland was colonized during various periods. Results Miocene floras of Iceland (15–6 Ma) show relatively high floristic turnover from the oldest floras towards the youngest; and few taxa from the oldest floras persist in the younger floras. The frequencies of the various dispersal mechanisms seen in the 15‐Ma floras are quite different from those recorded in the 6‐Ma floras, and there is a gradual change in the prevailing mode of dispersal from short‐distance anemochory and dyschory to long‐distance anemochory. Two mechanisms can be used to explain changing floral composition: (1) climate change, and (2) the interaction between the dispersal mechanisms of plants and the increasing isolation of proto‐Iceland during the Miocene. Main conclusions Dispersal mechanisms can be used to extract palaeogeographic signals from fossil floras. The composition of floras and dispersal mechanisms indicate that Iceland was connected both to Greenland and to Europe in the early Middle Miocene, allowing transcontinental migration. The change in prevalence of dispersal modes from 15 to 6 Ma appears to reflect the break‐up of a land bridge and the increasing isolation of Iceland after 12 Ma. Concurrent gradual cooling and isolation caused changes in species composition. Specifically, the widening of the North Atlantic Ocean prevented taxa with limited dispersal capability from colonizing Iceland, while climate cooling led to the extinction of thermophilous taxa.     

Soil carbon sequestration and land‐use change: processes and potential

When agricultural land is no longer used for cultivation and allowed to revert to natural vegetation or replanted to perennial vegetation, soil organic carbon can accumulate. This accumulation process essentially reverses some of the effects responsible for soil organic carbon losses from when the land was converted from perennial vegetation. We discuss the essential elements of what is known about soil organic matter dynamics that may result in enhanced soil carbon sequestration with changes in land‐use and soil management. We review literature that reports changes in soil organic carbon after changes in land‐use that favour carbon accumulation. This data summary provides a guide to approximate rates of SOC sequestration that are possible with management, and indicates the relative importance of some factors that influence the rates of organic carbon sequestration in soil. There is a large variation in the length of time for and the rate at which carbon may accumulate in soil, related to the productivity of the recovering vegetation, physical and biological conditions in the soil, and the past history of soil organic carbon inputs and physical disturbance. Maximum rates of C accumulation during the early aggrading stage of perennial vegetation growth, while substantial, are usually much less than 100 g C m^?2 y^?1. Average rates of accumulation are similar for forest or grassland establishment: 33.8 g C m^?2 y^?1 and 33.2 g C m^?2 y^?1, respectively. These observed rates of soil organic C accumulation, when combined with the small amount of land area involved, are insufficient to account for a significant fraction of the missing C in the global carbon cycle as accumulating in the soils of formerly agricultural land.     

Integration of transhumant pastoralism and irrigated agriculture in semi-arid East Africa

Agricultural development projects in the fertile and most well-watered areas of arid and semiarid Africa usually deny access to nomadic pastoralists whose production system and livelihood depend upon such areas in the dry season and during frequent droughts. The result can be degradation of range resources through overgrazing, and greater vulnerability of pastoralists. Recent calls for compatible land use schemes or nonexclusionary agricultural development projects in the context of pastoralist transhumance, suggest allowing pastoralists structured access to project sites in the dry season in order to utilize forage and water supplies. This paper examines the capacity of an irrigation scheme to support the seasonal influx of transhumant livestock in dry seasons of varying severity. The livestock carrying capacity of the existing mosaic of land use patterns and practices is used in the determination of the proportional areas of land use needed to absorb large seasonal concentrations of livestock.     

A general principle for the allocation of limited resources

Summary A marginal fitness theorem is derived for the allocation of a limited resource among alternative activities that have effects on the fitness of an individual. The marginal advantage theorem states that at the evolutionarily stable strategy (ESS), the marginal gains from increasing each of the allocations (expressed as partial derivatives of the fitness advantage of a rare mutant) are equal. The theorem is true for all proportional allocations (a + b + c + ...=j), regardless of the number of allocations, the nature of the response curves describing the direct effects of the allocations [f(a), etc.], or the way the effects of different allocations combine into fitness. The theorem is extended to size-number compromises and packaging strategies. The marginal advantage theorem is used to derive general theorems about the marginal effects of allocations [f (a), etc.] at the ESS and matching rules concerned with the total fitness to cost ratios of allocations at the ESS. The marginal advantage theorem is applicable to diverse allocation strategies, and provides a method for obtaining ESS allocations for any number of allocations and their components.     

Genetic diversity and environmental associations of wild barley,Hordeum spontaneum (Poaceae), in Iran

Genetic diversity and structure of populations of the wild progenitor of barleyHordeum spontaneum in Iran was studied by electrophoretically discernible allozymic variation in proteins encoded by 30 gene loci in 509 individuals representing 13 populations of wild barley. The results indicate that: a)Hordeum spontaneum in Iran is extremely rich genetically but, because of predominant self-pollination, the variation is carried primarily by different homozygotes in the population. Thus, genetic indices of polymorphismP-1% = 0.375, range = 0.267–0.500, and of genetic diversity,He = 0.134, range = 0.069–0.198, are very high. b) Genetic differentiation of populations includes clinal, regional and local patterns, sometimes displaying sharp geographic differentiation over short distances. The average relative differentiation among populations isGst = 0.28, range = 0.02–0.61. c) A substantial portion of the patterns of allozyme variation in the wild gene pool is significanctly correlated with the environment and is predictable ecologically, chiefly by combinations of temperature and humidity variables. d) The natural populations studied, on the average, are more variable than two composite crosses, and more variable than indigenous land races of cultivated barely,Hordeum vulgare, in Iran. — The spatial patterns and environmental correlates and predictors of genetic variation ofH. spontaneum in Iran indicate that genetic variation in wild barley populations is not only rich but also at least partly adaptive. Therefore, a much fuller exploitation of these genetic resources by breeding for disease resistance and economically important agronomic traits is warranted.     

A late Wenlock flora from Co. Tipperary, Ireland

An assemblage of macroplants preserved as highly coalified compressions which lack anatomy is described from a Wenlock locality in County Tipperary, Ireland. Most of the fertile specimens are assigned to Cooksonia Lang. The taxonomic status of this genus is discussed. Some poorly preserved palynomorphs, including miospores, acritarchs, chitinozoans and a variety of tubes, have been isolated from associated sediments, but the age of the flora is based on graptolites. Sedimentological and palaeontological studies of the region are summarized. They provide little direct evidence for the habitats of the plants which are considered to have been terrestrial. The relevance of this flora to the current debate on the colonization of the land is evaluated and it is concluded that these plants provide the earliest record of erect fertile land plants of possible pteridophyte affinity.     

四川大型真菌资源调查研究

本文介绍了四川大型真菌资源348种,包括药用真菌163种、食用真菌123种、有毒真菌41种、菌根真菌101种等。全国新记录26种。其中冬虫夏草(cordyceps sinensis)、凉山虫草(c.liangshanensis)、松口蘑(Tricholoma matsutake)、银耳(Tremella fuciformis)、短裙竹荪(Dictyophora duplicata)猴头(Hericium erinaceus)、鸡(土从)(Termitomyces albuminosus)、木耳(Auricuiaria auricula)、灵芝(Ganoderma lucidum)等尤为著名。并对四川大型真菌中部分重要种类的分布、资源及用途进行了分析和评价。为合理开发利用及有关教学科研提供了资料。     

沙地草场植物根系化学元素含量的特征

 本文报道了内蒙古沙地草场不同植物根系的化学元素含量特征。结果表明：51种植物根系的N、P、K、Si、Na、Fe和灰分的平均含量分别为1.08%、0.104%、0.686%、0.811%、0.049%、0.030%和6.416%。其中相同植物根系的N、P、K、Na和灰分的含量低于其地上部分的平均含量,而Si和Fe相反,根系的平均含量高于其地上部分。