多沙粗沙区林草植被建设对径流影响初析

依据以往的研究成果,针对多沙粗沙区北部、中部和西南部的实际情况,采用综合分析和统计的方法,在确定林草植被蒸散耗水量基础上,应用与坡地蒸散耗水量相对比的方法,分析了林草植被建设对径流量的影响。结果表明:①对于灌木草地来说,整个多沙粗沙区都能够满足其对水分的需求,而乔木林地在北部区基本上不能满足其需要。②林草植被蒸散耗水量的区域分布,与最大可能蒸发量的分布大体相似,而与降水量分布呈相反趋势,呈现出由西北向东南部递减以及自西向东减少的趋势;北部较中部乔灌草植被分别约偏多8%、10%和17%,而西南部较中部乔灌林地和人工草地分别偏多3%左右和约6%。③从水资源的适应性来说,多沙粗沙区适应乔木生长的区域还是有一定的限制。     

Decision-making in Water Management under Uncertainty

Decision-making in water management requires the delivery of accurate scientific information. However, the task is challenging under the situation where a large amount of uncertainty exists in the available information (e.g., model outputs). This paper investigates the effect of uncertainty on the ranking of options in water management. Different methods for ranking the management options under uncertainty are reviewed and they account for only partial uncertainty information in model outputs. To consider the full uncertainty information, a new ranking procedure is proposed in this paper, which is capable of providing more information to decision makers and at the same time taking their opinions on uncertainty into consideration. The ranking is achieved by conducting pair-wise comparison of management options, on the basis of the risk defined by the probability of obtaining an unacceptable ranking and the mean difference in model outputs in pair-wise comparison. An application example is presented to illustrate the use of the proposed ranking approach. Furthermore, the sensitivity of management option ranking to different ranking methods and to model uncertainty is also investigated.     

Quantifying the effect of riparian forest versus agricultural vegetation on river meander migration rates,central Sacramento River,California, USA

Riparian forest vegetation is widely believed to protect riverbanks from erosion, but few studies have quantified the effect of riparian vegetation removal on rates of river channel migration. Measured historical changes in a river channel centreline, combined with mapped changes in floodplain vegetation, provide an opportunity to test how riparian vegetation cover affects the erodibility of riverbanks. We analysed meander migration patterns from 1896 to 1997 for the central reach of the Sacramento River between Red Bluff and Colusa, using channel planform and vegetation cover data compiled from maps and aerial photography. We used a numerical model of meander migration to back‐calculate local values for bank erodibility (i.e. the susceptibility of bank materials to erosion via lateral channel migration, normalized for variations in near‐bank flow velocities due to channel curvature). A comparison of migration rates for approximately 50 years before and after the construction of Shasta dam suggests that bank migration rates and erodibility increased roughly 50%, despite significant flow regulation, as riparian floodplains were progressively converted to agriculture. A comparison of migration rates and bank erodibilities between 1949 and 1997, for reaches bordered by riparian forest versus agriculture, shows that agricultural floodplains are 80 to 150% more erodible than riparian forest floodplains. An improved understanding of the effect of floodplain vegetation on river channel migration will aid efforts to predict future patterns of meander migration for different river management and restoration scenarios. Copyright © 2004 John Wiley & Sons, Ltd.     

Effects of an enhanced flood on riparian plants of the River Murray,South Australia

In October 2000, the flow of the River Murray entering South Australia was increased from 32 000 to 42 050 ML day^?1 by release of water from an offstream reservoir, and a downstream weir was raised by 500 mm to impound the flood and enhance local floodplain inundation. The flood was maintained for about two weeks, although the duration of inundation was longer at low elevations on the floodplain. Vegetation at three sites was surveyed before and after the flood to examine the impact of inundation on the growth and germination of flood‐tolerant, flood‐dependent and flood‐intolerant species. Among 32 recorded species, Atriplex vesicaria (bladder saltbush, Chenopodiaceae), Sporobolus mitchellii (rats tail couch, Graminae) and Sarcocornia quinqueflora (samphire, Chenopodiaceae) accounted for nearly 82% of the total cover/abundance. Flood‐tolerant and flood‐dependent species (e.g. S. mitchellii) grew and germinated and flood‐intolerant species (e.g. A. vesicaria) senesced. No aquatic plants germinated or established, despite favourable conditions, suggesting an impoverished seed bank or grazing. Based on the growth but lack of germination of flood‐tolerant and flood‐dependent species, the value of small, occasional interventions in environmental flow management may be to maintain existing communities rather than restore degraded ones. Copyright © 2004 John Wiley & Sons, Ltd.     

城市绿地对热岛效应缓解作用研究——以保定市中心城区为例

随着中国城镇化建设的进行,城市热岛效应逐渐成为城市发展的显著问题之一,而城市绿地能有效地缓解城市热岛效应,在城市规划中,可以通过对城市绿地进行合理布局,从而减缓城市热岛效应的影响。本文采用遥感数据反演的方法,综合应用地理信息系统（GIS）和遥感（RS）技术,得到不同时期保定市中心城区地表温度和植被覆盖度的时空演变图,分析近10年的时空演变规律,并用网格法对植被覆盖度与地表温度之间的耦合关系进行研究,得出研究区内的植被覆盖度每增加10%,其地表的平均温度可减少0.9℃~1.3℃。选取研究区域内的8个城市绿地,利用缓冲区分析的方法,定量研究城市绿地面积与其降温范围之间的关系,结合保定市热岛效应集中区域及周边土地利用现状,提出增加城市绿地的可能位置,为城市绿地布局提供科学依据。     

澳大利亚植物园中的城市生物多样性设计与保护策略

由于景观起源、物理环境条件和社会经济发展的差异,在南北半球,学术界对城市生物多样性及其与生态设计方法的相互作用有着不同的理解。数千年来,澳大利亚本土植物群落在这片大陆繁衍生息,形成了生物多样性极高的独特景观。植物园融合自然和人造元素,具有科研和保育功能,其设计与规划反映了科学知识随时间变化的动态特征,也为研究不同社会群体在过去如何利用和重视植物提供了的独特视角,植物园的生态设计方法反映了重视和保护生物多样性的新愿景。以澳大利亚为例,研究并回顾了植物园在保护生物多样性方面的益处,讨论了为展示生物多样性植物园设计重点的变化,分析了澳大利亚植物园的设计历史、澳大利亚本土生物多样性以及以生物多样性为重点的设计解决方案。为了解澳大利亚当地生物多样性和制定植物园示范保护与策略提供研究框架,为重新思考和加强植物园设计中的"生物多样性"提供新视角。     

基于MODIS温度植被角度指数的农作物估产模型研究

利用MODIS数据,以河北石家庄和邢台地区冬小麦产量估算为例,探讨了综合植被指数与陆表温度的温度植被角度指数在农作物估产中的应用研究.首先,根据冬小麦物候历,计算了冬小麦抽穗期四种参量指数:归一化植被指数(NDVI)、增强型植被指数(EVI)、温度植被角度指数(TVA)和增强型温度植被角度指数(ETVA);其次,将实测的冬小麦产量数据与NDVI、EVI、VTA和EVTA数据进行回归分析,建立模型.结果表明,实测产量数据与这四种指数均具有很好的线性回归关系,相关系数R2均在0.60以上(分别为0.61、0.65、0.68、0.74),其中基于TVA和ETVA的估产模型要好于NDVI和EVI模型.由此可见,综合了MODIS光学反射和辐射信息的TVA/ETVA,能有效应用于实践估产中,并提高预测的准确性.     

城市植被景观规划的初探

从景观生态的角度,阐述了城市景观、城市植被景观规划的概念,植被的景观特点和景观功能,概括了植被景观规划理念与原则,初步探讨了城市植被景观规划中存在的问题,并提出了城市植被景观规划的一些建议。     

利用Fluent软件对植物坝覆盖区域流场的数值模拟

利用计算流体力学软件Fluent,用VOF方法追踪自由水面,对有植物坝覆盖的水槽二维两相流场进行数值模拟,采用多孔介质域模拟植物坝覆盖区域,以多孔介质前后压强配合孔隙率来确定渗透率。将数值计算得到的流速值与模型试验流速值实测结果进行比对,研究表明两者吻合较好。     

南水北调工程秦岭水源区保护与监测

阐述了秦岭及其水资源对当地社会、经济可持续发展和南水北调工程的重要意义;探讨了秦岭水源与生态环境的关系和水环境存在的问题,并就此提出了水源保护的策略,即恢复植被、控制旅游景区过度开发、治理污染、创建人工生态系统等;最后,针对秦岭水环境现状,较为详细地提出了水源保护监测的内容及方法.