城市化进程对地下河中溶解态正构烷烃来源的影响

为了探明城市化进程影响下地下河溶解态正构烷烃(D-ALK)的组分特征,于2014年11月至2015年4月,分别对受不同程度城市化进程影响的老龙洞与青木关两条地下河出口(老龙洞口、姜家泉)进行采样,利用气相色谱-质谱联用仪(GCMS)对样品中的D-ALK进行定量分析.结果表明,两地D-ALK碳数分布均为n C14~n C35.其中,姜家泉中的溶解态正构烷烃总量(DT-ALK)为102~356 ng·L~(-1),平均值为230 ng·L~(-1).2014年12月、2015年1月和4月,其正构烷烃碳数分布的峰型均为"单峰-前锋"型;LMH/HMH(n C-21/n C+22)为2.0~10;在n C14~n C25内碳优势指数(CPI14~25)为0.19~0.57,主碳峰均为C16(C_(max)16).2014年11月、2015年2月与3月,其碳数分布呈"双峰"形态,LMH/HMH与CPI14~25均小于1且C_(max)16;CPI24~35为1.2~23,C_(max)31或C_(max)33;Paq分别为0.2、0.7和0.1.其中,2014年11月与2015年3月的烷烃指数(AI)分别为0.95和0.98.老龙洞出口中的DT-ALK为110~697 ng·L~(-1),平均值为310 ng·L~(-1);各月碳数分布均呈现"单峰-前峰"峰型且C_(max)16,CPI14~25小于1.在旱季,由于受到不同人为活动的综合影响,以微生物输入为主的老龙洞中的溶解态正构烷烃在含量和组分的稳定性方面均大于以微生物和微生物、植物混合输入为主的姜家泉.     

杭州市城乡乔木物种的多样性

沿杭州市区至临安农村取1 km宽75 km长样带调查乔木物种多样性。调查结果表明市区本土树种保存较好,树种数量达到20余种,农村物种丰富度极低,树种数量仅有10种左右。从物种丰富度指数可以看出市区物种最为丰富,丰富度指数最高达4.343,郊区物种丰富度指数最低,为1.303,农村物种丰富度指数较郊区有所上升,但仍显著低...     

Simulating spatiotemporal dynamics of urbanization with multi-agent systems—A case study of the Phoenix metropolitan region, USA

Urbanization is a human-dominated process and has greatly impacted biodiversity, ecosystem processes, and regional climate. To understand the socioeconomic drivers of urbanization and project future urban landscape changes, multi-agent systems provide a powerful tool. We develop an agent-based model of urban growth for the Phoenix metropolitan region of the United States, which simulates the behavior of regional authorities, real estate developers, residents, and environmentalists. The BDI (Beliefs-Desires-Intentions) structure is employed to simulate the agents behavior and decision models. The heterogeneity of agents is reflected by adjusting parameters according to the agents’ beliefs, desires and preferences. Three scenarios, baseline, economic development priority and environmental protection, are developed and analyzed. The combination of multi-agent system and spatial regression model is employed to predict the future urban development of the Phoenix metropolitan region. Landscape metrics are used to compare the spatial patterns of the urban landscape resulting from different scenarios in different times. In general, with the rapid urban expansion, the shape of urban patches will become more regular as many of them become coalesced. The spatial analysis of urban development through modeling individual and group decisions and human-environment interactions with a multi-agent systems approach can enhance our understanding of the socioeconomic driving forces and mechanisms of urban development.     

URBAN IMPACTS ON PHYSICAL STREAM CONDITION: EFFECTS OF SPATIAL SCALE,CONNECTIVITY, AND LONGITUDINAL TRENDS1

ABSTRACT: An assessment of physical conditions in urban streams of the Puget Sound region, coupled with spatially explicit watershed characterizations, demonstrates the importance of spatial scale, drainage network connectivity, and longitudinal downstream trends when considering the effects of urbanization on streams. A rapid stream assessment technique and a multimetric index were used to describe the physical conditions of multiple reaches in four watersheds. Watersheds were characterized using geographic information system (GIS) derived landscape metrics that represent the magnitude of urbanization at three spatial scales and the connectivity of urban land. Physical conditions, as measured by the physical stream conditions index (PSCI), were best explained for the watersheds by two landscape metrics: quantity of intense and grassy urban land in the subwatershed and quantity of intense and grassy urban land within 500 m of the site (R²= 0.52, p > 0.0005). A multiple regression of PSCI with these metrics and an additional connectivity metric (proximity of a road crossing) provided the best model for the three urban watersheds (R²= 0.41, p > 0.0005). Analyses of longitudinal trends in PSCI within the three urban watersheds showed that conditions improved when a stream flowed through an intact riparian buffer with forest or wetland vegetation and without road crossings. Results demonstrate that information on spatial scale and patterns of urbanization is essential to understanding and successfully managing urban streams.     

城市化进程中的土地资源优化配置

土地资源的优化配置是目前我国城市化进程中面临的重要问题.在分析城市化的内涵和我国城市化进程的基础上,运用定性与定量相结合的方法,明确了城市化进程与土地资源优化配置的密切关系,阐述了城市化进程中土地利用存在的四大问题,提出了五大对策,以确保城市化进程中土地资源的优化配置.     

重庆市城镇化外部环境分析

从自然资源与生态环境的角度、人文与社会环境的角度、工农业等经济发展的角度对重庆市城镇化建设中的外部环境进行了深入分析，探讨了重庆市城镇化建设中具有的自身优势和存在的主要问题，以期能为重庆市城镇化建设提供一定的理论依据和参考价值。     

滨海半城市化地区植被覆盖度的时空变化——以青岛市崂山区为例

基于青岛市崂山区1990、1997、2002、2008年四期TM遥感影像数据,利用遥感二分像元估算模型和归一化植被指数,定量研究了半城市化地区的植被覆盖度演化过程及其时空动态变化特征,结果表明:研究区植被覆盖度演变具有快速性、差异性和不稳定性特征;1990-1997年,植被平均覆盖度由48.71%下降到24.74%,是植被覆盖度下降最快时期;2002-2008年间,植被平均覆盖度由23.58%增加到44.49%,属于植被覆盖恢复时期。整体空间变化呈现分散和无序特征,地形因子显著影响植被覆盖度的分布及变化。从气候因素和人为活动影响两个方面分析了造成崂山地区植被覆盖度下降的原因,对降雨量与各地区植被覆盖度进行了相关性分析,划分出气候影响显著区域。最后通过主成份分析定量研究气候、人为因素对当地植被覆盖度的影响程度,结果发现城市化作用是造成植被覆盖度变化的主要因素。     

Urbanization and Its Effect On Runoff in the Whiteoak Bayou Watershed,Texas1

Abstract: The capacity of a watershed to urbanize without changing its hydrologic response and the relationship between that response and the spatial configuration of the developed areas was studied. The study was conducted in the Whiteoak Bayou watershed (223 km²), located northwest of Houston, Texas, over an analysis period from 1949 to 2000. Annual development data were derived from parcel data collected by the Harris County Appraisal District. Using these data, measures of the spatial configuration of the watershed urban areas were calculated for each year. Based on regression models, it was determined that the annual runoff depths and annual peak flows depended on the annual precipitation depth, the developed area and the maximum 12‐h precipitation depth on the day and day before the peak flow took place. It was found that, since the early 1970s, when the watershed reached a 10% impervious area, annual runoff depths and peak flows have increased by 146% and 159%, respectively. However, urbanization is responsible for only 77% and 32% of the increase, respectively, while precipitation changes are responsible for the remaining 39% and 96%, respectively. Likewise, an analysis of the development data showed that, starting in the early 1970s, urbanization in the watershed consisted more of connecting already developed areas than of creating new ones, which increases the watershed’s conveyance capacity and explains the change in its response. Before generalizing conclusions, though, further research on other urban watersheds with different urbanization models appears to be necessary.     

基于生态服务价值的上海土地利用变化影响评价

基于Costanza的生态系统服务单价和我国国情,评估了上海中心城区1947~2006年土地利用变化对区域生态系统服务功能的影响.研究表明,60年间生态系统服务功能总体下降了87.96%,可分为缓慢减少、剧烈减少、趋缓减少和缓慢上升4个阶段,各阶段生态系统服务价值年均变化分别为-278.90×104,-2451.60×104,-88.89×104,36.66×104元/a.17类生态系统服务功能中,土壤侵蚀控制、栖息地、文化功能和扰动调节功能呈正增长,其中20年来绿地面积和绿化覆盖率持续增加是侵蚀控制功能和栖息地功能显著增加的主要原因.60年来水域面积大量减少使得水分调节和水供应功能的降幅巨大,两者对中心城区生态系统服务功能减少的贡献率为63.74%和24.33%.水域、耕地、绿地、城市住宅和公共建筑用地的生态系统服务功能变化,对中心城区生态系统服务功能减少的贡献率为99.57%,5.09%,-4.09%,-0.34%, -0.22%.除水域和耕地的生态系统服务功能显著下降外,其余均有上升,其中绿地的生态系统服务价值增幅最大,年增长率为19.45%.     

城市化影响下北京市外来入侵植物特征及其分布

通过文献资料分析和实地调查相结合的方法,对北京市外来入侵植物的种类、生活型、起源地、引入途径和分布等特征进行了分析,结果表明:该地区共有48种外来入侵植物,隶属39属19科,其中菊科、禾本科、苋科和大戟科植物为优势科,占到了所有入侵植物总数的60.4%.除火炬树外,其余47种植物均为草本植物,以起源于美洲的居多(70.8%),多为伴随种子苗木运输无意引进.入侵植物分布受城市化水平和人口密度影响显著,城市功能扩展区分布有最多的入侵植物,就入侵种分布密度而言,城市功能拓展区和城市核心区均明显高于近郊区和远郊区.目前北京入侵植物主要分布于农田、绿地、花圃等半人工生态系统,尚处于可控范围之内,但北京的自然地理条件及城市化进程使其仍存在较高的入侵风险,在将来的防治工作中应采取更加严格的检疫措施.