基于地统计学和15N技术的湿地土壤氮素 空间运移理论探讨

地统计学是探讨自然环境要素空间异质性的有效工具,它适合于定量研究区域化变量的空间结构变异特征。湿地土壤氮素是时空连续的变异体,不论尺度大小均具有高度的空间异质性,而其变量又属于区域化变量,同时具有随机性和结构性特征。因15N示踪技术能够示踪氮素物质的踪迹,而用15N标记的示踪体在湿地土壤中运移时所产生的丰度变化又具有空间异质性,故可考虑将二者结合起来来定量探讨湿地土壤氮素的空间运移。在此,就试对这一问题进行了较为系统和完整的理论探讨。     

乌拉盖开发区土地资源利用现状、模式与评价

本文利用RS、GIS的高新科技手段，结合外业调查，编制土地资源利用现状图，并建立土地资源数据库，快速、准确、实时地掌握了土地利用现状。对乌拉盖开发区土地资源利用现状进行综合分析，为该研究区域今后有效开发利用土地资源，实现持续发展提供了科学依据。     

Needles in haystacks: Estimating detection probability and occupancy of rare and cryptic snakes

The species most in need of conservation or management are often also the most difficult to monitor, because of their rarity, secretive habits, or both. To combat these challenges, presence/absence (site occupancy) models can be used to track species occupancy at landscape scales. However, quantitative knowledge of detection probability (which is almost always <1) is required to reliably estimate site occupancy. Here, we present a case study that combines detection probabilities and site occupancy modeling to monitor a notoriously secretive guild of animals, North American aquatic snakes. Specifically, we use program PRESENCE to estimate detection probability (p) and probability of site occupancy (ψ) for seven snake species in relationship to site covariates, to understand the proximate and ultimate factors that influence habitat suitability. We were able to estimate p (3–46%) and ψ (12–96%) for each species and calculate the amount of unsuccessful effort necessary to declare absence of each species with statistical confidence (5–63 visits; 150–1890 trap-nights). We documented considerable interspecific variation in p and ψ; one species (Nerodia fasciata) was widespread and highly detectable, while another (Agkistrodon piscivorus) had low detectability despite its wide distribution. Five other species were secretive, or restricted to specific habitat types, or both, illustrating that complex and sometimes counterintuitive relationships exist between capture rate and occupancy. Incorporating p and ψ is essential to the success of large-scale monitoring programs for elusive species.     

Plant species traits regulate methane production in freshwater wetland soils

Ecosystem and biogeochemical responses to anthropogenic stressors are the result of complex interactions between plants and microbes. A mechanistic understanding of how plant traits influence microbial processes is needed in order to predict the ecosystem-level effects of natural or anthropogenic change. This is particularly true in wetland ecosystems, where plants alter the availability of both electron donors (e.g., organic carbon) and electron acceptors (e.g., oxygen and ferric iron), thereby regulating the total amount of anaerobic respiration and the production of methane, a highly potent greenhouse gas. In this study, we examined how plant traits associated with plant inputs of carbon (photosynthesis and biomass) and oxygen (root porosity and ferric iron on roots) to mineral soils relate to microbial competition for organic carbon and, ultimately, methane production. Plant productivity was positively correlated with microbial respiration and negatively correlated to methane production. Root porosity was relatively constant across plant species, but belowground biomass, total biomass, and the concentration of oxidized (ferric) iron on roots varied significantly between species. As a result the size of the total root oxidized iron pool varied considerably across plant species, scaling with plant productivity. Large pools of oxidized iron were related to high CO₂:CH₄ ratios during microbial respiration, indicating that as plant productivity and biomass increased, microbes used non-methanogenic respiration pathways, most likely including the reduction of iron oxides. Taken together these results suggest that increased oxygen input from plants with greater biomass can offset any potential stimulation of methanogenic microbes from additional carbon inputs. Because the species composition of plant communities influences both electron donor and acceptor availability in wetland soils, changes in plant species as a consequence of anthropogenic disturbance have the potential to trigger profound effects on microbial processes, including changes in anaerobic decomposition rates and the proportion of mineralized carbon emitted as the greenhouse gas methane.     

中国湿地博物馆湿地景观展示特色分析

中国湿地博物馆是以展示湿地景观及文化为主题,集收藏、研究、展示、教育、宣传、娱乐于一体的大众化国家级专业博物馆。其湿地景观的塑造和表达特色明显,在总体设计、道路布局、空间疏理等方面都具有独到之处,且将各种类型的湿地景观化、情景化,在追求精密风格的同时,还夹杂着东方园林中的空间渗透与穿插的浪漫情结。现就中国湿地博物馆景观空间结构及形态设计进行分析,归纳出还原自然,虚实相交、柳暗花明,动态布局,步移景异等湿地景观展示特色。     

Urea hydrolysis in wetland soil amended with Sesbania aculeata green manure and rice straw

Summary The effect of incorporating sesbania and rice straw and of period of decomposition on urea hydrolysis was studied in a wetland soil under laboratory conditions. Urea hydrolysis proceeded more rapidly in the crop residue-amended soil than in the control soil, and increased with increases in the rate of addition of crop residues and with longer periods of decomposition. Irrespective of amendment treatment, urea hydrolysis followed first-order reaction kinetics, and rate constants in the unamended soil ranged from 0.021 to 0.024 h^-1 after urea application of 200 g N g^-1 soil. In the amended soil, hydrolysis rates ranged from 0.033 to 0.149 h^-1 with sesbania and 0.071 and 0.250 h^-1 with rice straw, depending on the length of decomposition period.     

Nitrogen fixation and beneficial effects of some grain legumes and green-manure crops on rice

Studies were conducted on paddy soils to ascertain N₂ fixation, growth, and N supplying ability of some green-manure crops and grain legumes. In a 60-day pot trial, sunhemp (Crotalaria juncia) produced a significantly higher dry matter content and N yield than Sesbania sesban, S. rostrata, cowpeas (Vigna unguiculata), and blackgram (V. mungo), deriving 91% of its N content from the atmosphere. Dry matter production and N yield by the legumes were significantly correlated with the quantity of N₂ fixed. In a lowland field study involving sunhemp, blackgram, cowpeas, and mungbean, the former produced the highest stover yield and the stover N content, accumulating 160–250 kg N ha^-1 in 60 days, and showed great promise as a biofertilizer for rice. The grain legumes showed good adaptability to rice-based cropping systems and produced a seed yield of 1125–2080 kg ha^-1, depending on the location, species, and cultivar. Significant inter- and intraspecific differences in the stover N content were evident among the grain legumes, with blackgram having the highest N (104–155 kg N ha^-1). In a trial on sequential cropping, the groundnut (Arachis hypogaea) showed a significantly higher N₂ fixation and residual N effect on the succeeding rice crop than cowpeas, blackgram, mungbeans (V. radiata), and pigeonpeas (Cajanus cajan). The growth and N yield of the rice crop were positively correlated with the quantity of N₂ fixed by the preceding legume crop.     

Effect of encapsulated calcium carbide on dinitrogen,nitrous oxide,methane, and carbon dioxide emissions from flooded rice

Summary The efficiency of N use in flooded rice is usually low, chiefly due to gaseous losses. Emission of CH₄, a gas implicated in global warming, can also be substantial in flooded rice. In a greenhouse study, the nitrification inhibitor encapsulated calcium carbide (a slow-release source of acetylene) was added with 75, 150, and 225 mg of 75 atom % ¹⁵N urea-N to flooded pots containing 18-day-old rice (Oryza sativa L.) plants. Urea treatments without calcium carbide were included as controls. After the application of encapsulated calcium carbide, 3.6 g N₂, 12.4 g N₂O-N, and 3.6 mg CH₄ were emitted per pot in 30 days. Without calcium carbide, 3.0 mg N₂, 22.8 g N₂O-N, and 39.0 mg CH₄ per pot were emitted during the same period. The rate of N added had a positive effect on N₂ and N₂O emissions, but the effect on CH₄ emissions varied with time. Carbon dioxide emissions were lower with encapsulated calcium carbide than without. The use of encapsulated calcium carbide appears effective in eliminating N₂ losses, and in minimizing emissions of the greenhouse gases N₂O and CH₄ in flooded rice.     

Soils of a dune coastal salt marsh system in relation to groundwater level,micro-topography and vegetation under a semiarid Mediterranean climate in SE Spain

Twenty-one soil profiles were described, analysed and classified in a salt marsh dune system in SE Spain. Sites for sampling were selected according to micro-topographical positions and vegetation types. The pedons showed an A–C type profile. Most of the profiles at summit positions had a microbiotical crust in the upper centimetres, formed by fungal mycelia that contribute to agglutination of sand particles. In two soils, a buried Ab horizon could be identified. Soils at inter-dune depressions showed redoximorphic features with diffuse boundaries, therefore indicating the actual activity of the oxidation–reduction processes. The presence of remains of Posidonia oceanica buried in many of the profiles indicates both a progressive regression of the shoreline and the accretion of the dune system. Sand grains were the most abundant size fraction (generally higher than 65%). Salinity strongly increased at the depressions, with Cl⁻, SO₄²⁻, Na⁺ and Mg²⁺ being the most abundant ions. The microtopographical position at the dune had more influence on the vegetation cover and the soil type than did the distance to the shoreline. Most of the profiles at summit sites were colonised by trees (Pinus halepensis and Juniperus phoenicea subsp. turbinata), shrubs (Pistacea lentiscus, Rhamnus lycioides), thyme-brushwoods (Crucianella maritima, Teucrium dunense) or grasses (Ammophila arenaria), and they were classified as Arenosols or Torripsammens. The slopes of the depressions were dominated by Schoenus nigricans, living on Gleysols or Halaquepts and Aquisalids, or Limonium cossonianum, living on Solonchaks or Aquisalids. Juncus maritimus occupied footslope or bottom positions of the depressions, growing on Solonchaks or Aquisalids and Gleysols or Halaquepts. The succulent halophytes Arthrocnemum macrostachyum and Sarcocornia fruticosa were typical species at bottom positions, living on Solonchaks and Fluvisols or Aquisalids. In two of the profiles at interdune depressions a petrocalcic horizon appeared.     

Reedbeds as refuges for water voles (Arvicola terrestris) from predation by introduced mink (Mustela vison)

The water vole has recently undergone a catastrophic decline in the UK. This has resulted from loss and fragmentation of suitable habitat leaving water vole populations highly vulnerable to the impact of predation by introduced American mink. However, at some reedbed sites water voles and mink have apparently coexisted for many years. To determine if reedbeds offer a refuge from predation, 70 voles were radio-tagged at three sites in England and overwinter mortality monitored. Water vole perception of predation risk was also assessed. Mortality was high (64%), predation by mustelids, including mink, being the chief cause. Experiments suggested that voles failed to perceive areas of highest predation risk. However, predation rate declined strongly with the distance water voles lived from a main water channel. Thus, reedbeds provide a refuge from predation, even by mink, and calculations suggest that they may support source populations enhancing the viability of water vole metapopulations. Consequently reedbeds are now being used as one focus for the conservation of water voles in England and Wales.