黄土丘陵区小流域土壤碳氮比的变化及其影响因素

研究土壤C:N的变化有助于深入理解土壤有机碳氮的积累过程及其土壤质量的变化趋势。以黄土高原丘陵沟壑区砖窑沟小流域为单元,基于地貌类型和土地利用方式两大因素,采集737个土壤样品,研究流域内土壤C:N的变化差异及其影响因素。梁峁坡上,林地和草地0~20 cm土层的土壤C:N分别是农田土壤C:N的1.13和1.03倍;沟坡上,林地、草地和农田土壤的C:N分别为13.88、12.58、9.02。农田条件下,梁峁坡、沟坡和沟谷的土壤C:N分别为10.34、9.02和10.77;林地条件下,沟坡和梁峁坡的土壤C:N分别为13.88、11.67;草地条件下,沟坡土壤C:N是梁峁坡土壤C:N的1.19倍。同一地貌类型或土地利用方式条件下,土壤C:N均呈现表层大于深层的趋势,0~20 cm和20~40 cm土层的土壤C:N分别是40~100 cm土层土壤C:N的1.05~1.17和1.16~1.42倍。     

定量评估气候变化对长江中下游地区植被GPPGS变化的影响

在区域和植被类型尺度上定量厘定气候因子对长江中下游地区生长季植被GPP（GPP_GS）的直接、间接和综合影响,可为全球气候变化背景下区域植被资源管理与恢复提供科学依据.利用MODIS GPP数据、气象数据和植被类型数据,结合Theil-Sen Median趋势分析和Mann-Kendall显著性检验探究长江中下游地区植被GPP_GS时空变化特征,并通过通径分析揭示气候因子对长江中下游地区整体和不同类型植被GPP_GS变化的直接影响、间接影响和综合影响.结果表明：①2000~2021年长江中下游地区植被GPP_GS呈波动上升趋势,上升速率（以C计,下同）为2.70 g·（m²·a）^-1 （P<0.01）.不同类型植被GPP_GS均呈极显著上升趋势（P<0.01）,其中,灌丛上升速率最高,为3.31 g·（m²·a）^-1,栽培植被上升速率最低,为2.54 g·（m²·a）^-1.②长江中下游地区GPP_GS呈上升趋势的面积占比为88.11%.不同类型植被GPP_GS呈上升趋势的面积占比均大于84%.③通径分析结果表明,降水和最高气温对植被GPP_GS的直接影响呈显著正向影响（P<0.05）,而太阳辐射呈不显著正向影响（P≥0.05）.最高气温、降水和太阳辐射对植被GPP_GS的间接影响均呈非显著负向影响（P≥0.05）.在直接影响和间接影响的综合作用下,降水和最高气温对植被GPP_GS呈不显著正向影响（P≥0.05）,而太阳辐射对植被GPP_GS呈不显著负向影响（P≥0.05）;不同植被类型上,降水是影响栽培植被GPP_GS变化的主要气候因子,最高气温是影响针叶林、阔叶林、灌丛和草丛GPP_GS变化的主要气候因子.④长江中下游地区植被GPP_GS变化主要受最高气温、降水和太阳辐射的直接影响,降水的直接影响对植被GPP_GS变化的主导区域占56.72%.研究结果可为量化长江中下游地区植被固碳潜力和全球气候变化背景下制定因地制宜的生态恢复治理政策提供参考.     

Detecting general plant functional type responses in fragmented landscapes using spatially-explicit simulations

Habitat loss and increasing landscape fragmentation are known to be key forces driving the ongoing loss of plant species diversity. While the combined effects of increasing isolation and decreasing population size have been studied intensively; it is less understood how plant population performance in heterogeneous landscapes is affected by changes in fragmentation alone.     

县域单元美丽乡村建设类型划分与生态廊道构建——以浙江省德清县为例

基于第一次地理国情普查数据,以浙江省德清县为例,探讨县域单元美丽乡村建设类型划分和生态廊道建设。首先,基于自然本底,将村域单元划分为3种类型:山地景观型、丘陵风光型和平原水乡型;在此基础上,考虑城市未来扩展空间,增加都市风貌型,最终将美丽乡村建设划分为4种类型。其次,依据资源空间分布,评价各个村域单元美丽乡村建设潜力,将所有村域分为3个等级:核心建设村落、重点建设村落和一般建设村落。第三,识别出对德清具有重要生态意义的6个生态保护区,考虑不同地表覆盖景观格局对动物迁移的阻碍差异,利用GIS空间分析方法,计算出迁徙成本最小的路径,识别出4条重要的生态廊道。第四,将识别的生态廊道与地表覆盖进行匹配调整分析,最终构建起德清县“六核心、四廊道”的生态空间格局。     

Suitability of the vegetation types in Mexico's Tamaulipas state for the siting of hazardous waste treatment plants

A land suitability study was carried out by applying a multiple-criteria technique to 12 different vegetation types in Mexico's Tamaulipas state to help select potentially suitable sites for hazardous waste treatment plants. Species richness, spatial distribution, and uniqueness were selected as the criteria for estimating a vegetation type's suitability. Using the analytical hierarchy process, we ranked and mapped vegetation types, then compared the results with rankings of the same vegetation types based only on their number of endemic species. The suitabilities of the various vegetation types were ordered in more or less the same way by both methods, except in two cases for which the results were very different. The method proved to be a useful tool despite the availability of only partial (mostly qualitative) information; under such circumstances, expert experience can be incorporated in the evaluation process to a limited degree. The technique described in this paper has a high potential to aid decisions when many opinions and options must be considered simultaneously.     

混凝土生态膜污水处理工艺生物相变化研究

通过试验方法,研究了混凝土生态膜污水处理工艺的循环挂膜过程,综合考察了混凝土膜片表面生物膜的生长变化情况,细菌数量及其微型动物的组成演化。同时在挂膜一定时间后投加生活污水,考察对COD、NH3-N的去除率。     

呼伦贝尔市城郊河岸带土壤与河流沉积物重金属污染现状分析

河岸带类型对河流环境重金属富集具有显著影响,合理规划河岸环境,可以减缓河流周围土地的重金属污染对河流生态系统的影响。随着内蒙古自治区呼伦贝尔市工矿业、农牧业和旅游业的快速发展,频繁的人类活动会增加对河流周边重金属污染潜在威胁。为揭示呼伦贝尔市河流域环境重金属污染的现状、分布特征以及不同的河岸带类型对河流沉积物重金属污染的影响,在该区域采集了34个河岸带表层土壤和河流表层沉积物样品,并测定了6种重金属（Cr、Cu、Mn、Ni、Pb与Zn）含量,采用污染负荷指数法（pollution load index,PLI）对重金属污染情况进行评价。结果显示：6种重金属的平均含量分别为背景值的2.08倍、1.55倍、0.80倍、1.61倍、0.82倍、1.00倍,总体PLI为1.19,属轻度污染;河岸带的重金属污染程度总体高于河流,但是河流的重金属污染变率更大,相比之下重金属含量的最高值多出现于河流中;不同河岸带类型的PLI呈工业型河岸最高（1.535）、自然型河岸次之（1.126）、城市绿化河岸最低（1.030）、工矿业活动是区域重金属污染的主要源头,城市绿化型河岸带与自然型河岸带具有一定的缓解重...     

The effects of disturbance based management on the dynamics of Mediterranean vegetation: A hierarchical and spatially explicit modeling approach

The eastern Mediterranean region has been subjected to intensive human disturbance in the past 10,000 years, mainly in the forms of agro-pastoral activities such as grazing, shrub clearing, and prescribed burning. This disturbance history resulted in the formation of highly heterogeneous landscapes, characterized by high biodiversity. Recent changes in human activities have resulted in a decrease of landscape heterogeneity, leading to decreasing biodiversity and increasing fire risk. To conserve heterogeneity, land managers apply disturbance based management practices, using the same activities that created and maintained landscape heterogeneity in the past. However, the long-term and large-scale outcomes of these disturbances are often unknown, due to the complex response of Mediterranean vegetation to disturbance. Here we report on a spatially explicit, hybrid, and spatially hierarchical ecological model developed by us. The model attempts to predict the outcome of various disturbance based management activities on the long-term spatio-temporal dynamics of five common Mediterranean vegetation types. The model uses a spatially explicit state and transition formulation, with continuous transition functions. Model simulations were conducted on a Mediterranean landscape in Northern Israel, incorporating various disturbance practices that are common in the region. Simulation results highlight the potential of disturbance based management as a tool for conserving landscape heterogeneity, as well as the complex interactions between disturbances and the spatial structure of the landscape in Mediterranean regions.     

MODELING DEVELOPED COASTAL WATERSHEDS WITH THE AGRICULTURAL NON-POINT SOURCE MODEL1

ABSTRACT: Many coastal states are facing increasing urban growth along their coast lines. The growth has caused urban non-point source nitrogen runoff to be a major contributor to coastal and estuarine enrichment. Water resource managers are responsible for evaluating the impacts from point and non-point sources in developed watersheds and developing strategies to manage future growth. Non-point source models provide an effective approach to these management challenges. The Agricultural Non-Point Source Model (AGNPS) permits the incorporation of important spatial information (soils, landuse, topography, hydrology) in simulating surface hydrology and nitrogen non-point source runoff. The AGNPS model was adapted for developed coastal watersheds by deriving urban coefficients that reflect urban landuse classes and the amount of impervious surface area. Popperdam Creek watershed was used for model parameter development and model calibration. Four additional watersheds were simulated to validate the model. The model predictions of the peak flow and total nitrogen concentrations were close to the field measurements for the five sub-basins simulated. Measured peak flow varied by 30 fold among the sub-basins. The average simulated peak flow was within 14 percent of the average measured peak flow. Measured total nitrogen loads varied over an order of magnitude among the sub-basins yet error between the measured and simulated loads for a given sub-basin averaged 5 percent. The AGNPS model provided better estimates of nitrogen loads than widely used regression methods. The spatial distribution of important watershed characteristics influenced the impacts of urban landuse and projecting future residential expansion on runoff, sediment and nitrogen yields. The AGNPS model provides a useful tool to incorporate these characteristics, evaluate their importance, and evaluate fieldscale to watershed-scale urban impacts.     

Motor Vehicle Crashes on Bridges and Countermeasure Opportunities

There are approximately 600,000 highway bridges in the United States. These structures differ from surface streets and highways in terms of their physical properties and operational characteristics, which in turn, affect the risk of motor-vehicle crashes and the kinds of crashes that occur. The purpose of this study was to identify motor-vehicle crash patterns and contributing factors to bridge crashes and related countermeasure opportunities on four urban bridges in the New York metropolitan area. A crash typology was developed using the narratives and diagrams in police crash reports in addition to standard police classifications of crashes. The final dataset contained records of 1,381 police-reported crashes. The four bridges studied had higher crash rates than their respective approach roads. Four major crash types accounted for approximately 90% of the bridge crashes. Primary collision factors are reviewed, and potential countermeasures are discussed.