气象要素对草面温度的影响分析及其质量控制方法

运用天气学原理,分析天气现象变化(辐射、云、降水、风)与草温变化的密切关系,找出草面温度的各种不同天气变化规律,对草面温度观测资料进行质量控制.     

The effects of initial soil moisture conditions on swale flow hydrographs

The effects of soil water content (SWC) on the formation of run‐off in grass swales draining into a storm sewer system were studied in two 30‐m test swales with trapezoidal cross sections. Swale 1 was built in a loamy fine‐sand soil, on a slope of 1.5%, and Swale 2 was built in a sandy loam soil, on a slope of 0.7%. In experimental runs, the swales were irrigated with 2 flow rates reproducing run‐off from block rainfalls with intensities approximately corresponding to 2‐month and 3‐year events. Run‐off experiments were conducted for initial SWC (SWC_ini) ranging from 0.18 to 0.43 m³/m³. For low SWC_ini, the run‐off volume was greatly reduced by up to 82%, but at high SWC_ini, the volume reduction was as low as 15%. The relative swale flow volume reductions decreased with increasing SWC_ini and, for the conditions studied, indicated a transition of the dominating swale functions from run‐off dissipation to conveyance. Run‐off flow peaks were reduced proportionally to the flow volume reductions, in the range from 4% to 55%. The swale outflow hydrograph lag times varied from 5 to 15 min, with the high values corresponding to low SWC_ini. Analysis of swale inflow/outflow hydrographs for high SWC_ini allowed estimations of the saturated hydraulic conductivities as 3.27 and 4.84 cm/hr in Swales 1 and 2, respectively. Such estimates differed from averages (N = 9) of double‐ring infiltrometer measurements (9.41 and 1.78 cm/hr). Irregularities in swale bottom slopes created bottom surface depression storage of 0.35 and 0.61 m³ for Swales 1 and 2, respectively, and functioned similarly as check berms contributing to run‐off attenuation. The experimental findings offer implications for drainage swale planning and design: (a) SWC_ini strongly affect swale functioning in run‐off dissipation and conveyance during the early phase of run‐off, which is particularly important for design storms and their antecedent moisture conditions, and (b) concerning the longevity of swale operation, Swale 1 remains fully functional even after almost 60 years of operation, as judged from its attractive appearance, good infiltration rates (3.27 cm/hr), and high flow capacity.     

杭锦旗北部牧草引种试验

利用在内蒙古杭锦旗北部进行牧草引种试验的数据,结合产量效益分析了4个牧草品种对当地土壤与气候条件的适应性,初步得出适应杭锦旗北部气候、生态条件的牧草品种,并通过产量效益分析,确定了适合当地的牧草间、混作模式,为当地建立人工饲草基地发展生态畜牧业提供决策参考。     

Comparison of intestinal bacterial communities in grass carp, Ctenopharyngodon idellus, from two different habitats

The intestinal bacteria of vertebrates form a close relationship with their host.External and internal conditions of the host,including its habitat,affect the intestinal bacterial community.Similarly,the intestinal bacterial community can,in turn,influence the host,particularly with respect to disease resistance.We compared the intestinal bacterial communities of grass carp that were collected from farm-ponds or a lake.We conducted denaturing gradient gel electrophoresis of amplified 16S rRNA genes,from which 66 different operational taxonomic units were identified.Using both the unweighted pair-group method with arithmetic means clustering and principal component analysis ordination,we found that the intestinal bacterial communities from the two groups of pond fish were clustered together and inset into the clusters of wild fish,except for DF-7,and there was no significant correlation between genetic diversity of grass carp and their intestinal bacterial communities(Mantel one-tailed test,R=0.157,P=0.175).Cetobacterium appeared more frequently in the intestine of grass carp collected from pond.A more thorough understanding of the role played by intestinal microbiota on fish health would be of considerable benefit to the aquaculture industry.     

Chelant‐assisted Phytostabilization of Paint‐contaminated Residential Sites

Following the basic incubation study, a greenhouse experiment was conducted to elucidate the efficiency of vetiver grass (Vetiveria zizanioides L.), with or without chelating agents, in remediating lead (Pb)‐contaminated soils from actual residential sites where Pb‐based paints were used. Because the primary factor affecting Pb phytoavailability in soils is soil pH, we used two soil types widely varying in pH that have total Pb concentrations above 1500 mg kg^?1 soil. Lead‐contaminated, low pH, acidic soils were collected from residential sites in Baltimore, MD and high pH, alkaline soils were collected from residential sites in San Antonio, TX. Based on the soil characterization results, two most appropriate soils (one from each city, having similar Pb levels but variable soil physico‐chemical properties) were selected for this study. Ethylenediaminetetraacetic acid (EDTA) and [S,S′]ethylenediaminedisuccinate (EDDS) were applied at 5, 10, and 15 mmol kg^?1 soil. Lead uptake and translocation in vetiver was determined on day 10 after chelants addition. Plant and soil analysis show that EDTA treated soils have maximum Pb uptake and lower total soil Pb levels. Prediction models developed for exchangeable Pb show a strong correlation for total Pb accumulated in vetiver grass. Results of the sequential chemical extraction of the soils at both initial and final time‐points, indicates a significant mobilization of Pb by the two chelants from carbonate‐bound fraction to exchangeable pool. Information on physico‐chemical properties of contaminated residential soils help in predicting Pb phytoextraction and thus further help in calibrating a successful chelant‐assisted phytoremediation model.     

Range expansion and potential distribution of the invasive grass Bromus tectorum in southern South America on the base of herbarium records

We reconstructed the invasion history and modelled the potential distribution of the invasive grass Bromus tectorum in southern South America. On the base of herbarium data, we described two aspects of B. tectorum's range expansion over time: area of occupancy and extent of occurrence. A maximum entropy model was used to identify both climatic variables associated with B. tectorum's current distribution and potentially invasible areas. The area-of-occupancy curve showed a steady increase of the occupied area since the first collection in 1937, with no obvious asymptote. However, the extent-of-occurrence curve indicated that range expansion was not homogeneous through time, but faster between 1965 and 1980. Most invasible areas were arid and semiarid with markedly Mediterranean precipitation regime. Within this susceptible region, there were large areas containing only a few known records of B. tectorum. Our results indicate that B. tectorum has successfully expanded over much of southern South America. In addition, there seems to be room for further local invasion (i.e. an increase of its area of occupancy) over large susceptible areas within the invaded region. Overall, our results confirm the suitability of southern South America's arid environments to B. tectorum invasion, and stress the importance of long-distance dispersal in accelerating its expansion across the region.     

不同经济水平牧户草场植被特征比较

以内蒙古荒漠草原家庭牧场为研究尺度,比较分析了不同经济水平牧户草场的植物群落特征,结果表明:主要植物种群的高度、盖度、密度、地上生物量、重要值及群落多样性指数均呈现出不同程度的趋同性.从社会学角度分析表明,牧区牧户的经济收入与饲养牲畜头数呈高度正相关.不同经济水平牧户草畜平衡的调整和适应能力不同,低经济水平牧户一般牲畜头数少,草场相对可使用面积大,经营意识薄弱,草场经常被有意或无意占用;中等经济水平牧户扩大饲养规模的愿望最为强烈,并积极通过围封、租借草场等方式来保护自家草场和扩大牲畜数量;高经济水平牧户则普遍采取常年租借草场、走场、购买饲草料等措施,减缓对自己草场放牧压力,同时保持畜饲养规模的维持和扩大.牧户存在调整适应行为,并会基于自己的“草畜平衡标准”,根据经济条件、草场面积、牲畜数量和对草场状况、放牧超载及效益的认知,适时通过草场流转和输入外部资源等方式,转移放牧压力,致使不同牧户草场生态状况趋于一致.     

Temporal variability in the life history and reproductive biology of female dugongs in Torres Strait: The likely role of sea grass dieback

The extensive sea grass meadows in Torres Strait enable it to be a globally important habitat for the dugong, Dugong dugon, a marine mammal of cultural and dietary significance to Torres Strait Islanders and the basis for the substantial island-based fishery in the Torres Strait Protected Zone. Torres Strait sea grass communities are subjected to episodic diebacks which are now believed to be largely natural events. Information on dugong life history was obtained from specimens obtained from female dugongs as they were butchered for food by Indigenous hunters at two major dugong hunting communities in Torres Strait: Daru (9.04°S, 143.21°E) in 1978–1982 (a time of sea grass dieback and recovery) and Mabuiag Island (9.95°S, 142.15°E) in 1997–1999 (when sea grasses were abundant). Dugongs sampled in 1997–1999 had their first calf at younger ages (minimum of 6 cf. 10 years), and more frequently (interbirth interval based on all possible pregnancies 2.6±0.4 (S.E.) yr cf. 5.8±1.0 yr) than the dugongs sampled in 1978–1982. Pregnancy rates increased monotonically during 1978–1982, coincident with sea grass recovery. The age distribution of the female dugongs collected in 1997–1999 also suggested a low birth rate between 1973 and 1983 and/or or a high level of mortality for animals born during this period. These results add to the evidence from other regions that the life history and reproductive rate of female dugongs are adversely affected by sea grass loss, the effect of which cannot be separated from a possible density-dependent response to changes in dugong population size. Many green turtles in Torres Strait were also in poor body condition coincident with the 1970s sea grass dieback. The impacts of future sea grass diebacks need to be anticipated when management options for the traditional Torres Strait fisheries for dugongs and green turtles are evaluated.     

植被作用下土壤抗剪强度和径流侵蚀力的耦合效应

利用野外径流小区动态监测和人工模拟降雨试验,阐明了草被和灌木的减流减沙效应,从力学层面揭示了坡面侵蚀产沙的过程机理。结果表明,与裸地相比,野外坡面草地和灌木地径流量分别减少28.1%~56.5%和85.7%~100%、产沙量分别减少84.9%~90.7%和98.5%~100%;在人工模拟降雨强度下,草地和灌木地径流量分别减少51.9%~90.9%和61.7%~80.6%、产沙量分别减少93.6%~99.2%和95.5%~99.2%;植被具有明显的增强土壤抗剪强度的作用,不同植被坡面抗剪强度与剪切面上的法向压力成正比,且符合库仑定律;不同下垫面条件下土壤黏聚力与坡面径流量和侵蚀产沙量呈显著的负相关关系,随着黏聚力的增大,径流量和侵蚀产沙量呈下降趋势;草地和灌木地坡面侵蚀临界径流切应力分别为裸地的2.64~3.16倍和2.44~3.18倍,建立了不同被覆坡面临界径流切应力与土壤抗剪强度和黏聚力的关系。研究结果对定量评价植被减蚀作用和深化土壤侵蚀力学过程有一定的参考意义。     

青海湖布哈河流域树轮宽度指数与NDVI植被指数的关系

利用来自青海湖流域乌兰和天峻的树轮指数和1982-2003年逐月标准化植被指数(NDVI)数据及气候数据, 在分析树轮指数及草地NDVI与气候因子关系的基础上, 探讨了树轮宽度指数序列与青海湖布哈河流域草地NDVI之间的关系.结果表明: 树轮宽度指数及草地NDVI主要受6-8月份的水热条件的影响, 温度与同期树轮宽度指数及草地NDVI具有较高的正相关, 而降水的影响存在滞后性.树木年轮指数序列与6-8月草地NDVI有显著的相关关系, 与8月份的NDVI相关性最强.树轮指数与草地NDVI间的显著相关性为研究该地区草地过去的动态变化提供了基础, 利用乌兰和天峻的两条树轮指数重建了8月份NDVI的千年变化.