西北干旱区河西走廊荒漠绿洲土地覆盖类型与蒸散的关系研究——基于Landsat 8和ZY3数据融合

蒸散是地表水热平衡的重要分量,也是陆地生态过程与水文过程之间的重要纽带,尤其在干旱区地-气相互作用、碳循环、水循环等过程所包含的物质与能量交换中占有极其重要的地位。基于Landsat 8遥感影像和资源三号影像(ZY3)的高分辨率植被信息,利用SEBS模型对西北干旱区河西走廊中段临泽绿洲北部区域地表蒸散量进行了估算,并用绿洲内部和绿洲-荒漠过渡带两个通量塔涡动相关数据对模型进行评估,分析了不同土地覆盖类型对蒸散量空间分布的影响。结果表明:(1)SEBS模型模拟值与实测日蒸散值之间拟合效果较好,且在均一地表时(绿洲农田区)估算精度更高(R~2=0.96,P0.001),RMSE、MAE分别为0.84 mm/d、0.56 mm/d;(2)从季节变化来看蒸散量与作物生长密切相关,夏季灌溉和降雨使得研究区水分充足,植被覆盖度高,蒸散量相应增加,在绿洲地区可达5.95 mm/d,而冬季最小仅为0.52 mm/d;(3)从蒸散量的空间变化来看,水体蒸散值最大,其余依次为农田、防护林、裸地和灌木丛,说明除水体外,随着植被覆盖的增大,蒸散量也逐渐增加。通过ZY3影像的高分辨率植被信息与Landsat 8影像热红外数据融合,提高了SEBS模型对该区域蒸散量的模拟效果,增进了我们对绿洲下垫面与大气间水热交换规律、水文过程、生态-水文相互作用的深入理解。     

不同植被条件下实际蒸散的变化特征及其影响因子——以淮河流域为例

基于遥感-过程耦合模型开展淮河流域2001—2012年实际蒸散(ET)的模拟研究,并对其时空变化特征、不同覆被类型下的区域实际蒸散特征及其主要影响因子进行定量分析.结果表明: 研究期间,研究区年均ET在空间上呈现由东南向西北逐渐递减的趋势;时间上呈现逐年增加趋势,月际波动为双峰变化曲线.不同植被类型下ET的差异性表现为: 农田对研究区域实际蒸散总量的贡献最大;混交林的年均单位面积实际蒸散量最大,裸地的年均单位面积实际蒸散量最小;除裸地以外,其他土地覆被类型年均实际蒸散都呈增长趋势,其中常绿阔叶林实际蒸散增加趋势最明显.平均温度等热力学因子是影响淮河流域实际蒸散的主导因子,其次是辐射因子和水分因子.     

基于能流物流理论的农牧交错带生态治理模式研究——以内蒙古后山旱农区为例

中国北方农牧交错带的生态环境问题引起了人们广泛关注．经过多年的攻关研究。以能物流理论为指导,根据地处北方农牧交错带的后山旱农区的自然、社会、经济特征,提出了以丘陵为单元的生态治理模式,1999年对传统顺坡种植模式、人工草地模式和生态治理模式进行观测．能物流分析结果表明。生态治理模式与传统的种植模式相比,能提高太阳能利用率8．3％,提高能量输出量8．7％,提高能量转化效率19．4％,N的输出量提高26．5％,转化效率提高57．1％,P的输出量提高12．1％,转化效率提高45．0％。水分利用效率提高17．7％．人工草地模式与传统模式和生态治理模式相比,其太阳能利用率、能量输出量、能量转化效率都是最低的．治理模式产出最多,盈利最多,是经济效益最好的模式,经济效率比传统模式提高16．1％。     

Shrub encroachment effect on the evapotranspiration and its component—A numerical simulation study of a shrub encroachment grassland in Nei Mongol,China

Aims Shrub encroachment is a common global change phenomenon occurring in arid and semi-arid regions. Due to the difficulty of partitioning evapotranspiration into shrub plants, grass plants and soil in the field, there are few studies focusing on shrub encroachment effect on the evapotranspiration and its component in China. This study aims to illustrate shrub encroachment effect on evapotranspiration by the numerical modeling method. Methods A two-source model was applied and calibrated with the measured evapotranspiration (ET) by the Bowen ratio system to simulate evapotranspiration and its component in a shrub encroachment grassland in Nei Mongol, China. Based on the calibrated model and previous shrub encroachment investigation, we set three scenarios of shrub encroachment characterized by relative shrub coverage of 5%, 15% and 30%, respectively, and quantified their effects caused by shrub encroachment through localized and calibrated two-source model.Important findings The two-source model can well reconstruct the evapotranspiration characteristics of a shrub encroachment grassland. Sensitivity analysis of the model shows that errors for the input variables and parameters have small influence on the result of partitioning evapotranspiration. The result shows that shrub encroachment has relatively small influence on the total amount of ET, but it has clear influence on the proportion of the components of evapotranspiration (E/ET). With shrub coverage increasing from 5% to 15% and then 30%, the evapotranspiration decreased from 182.97 to 180.38 and 176.72 W·m^-2, decreasing amplitude values of 0.34% and 0.44%, respectively. On average, E/ET rises from 52.9% to 53.9% and 55.5%, increasing amplitude values to 2.04% and 3.25%. Data analysis indicates that shrub encroachment results in smaller soil moisture changes, but clear changes of ecosystem structure (decreasing ecosystem leaf area index while increasing vegetation height) which lead to the decrease of transpiration fraction through decreasing canopy conductance. The research highlights that, with the shrub encroachment, more water will be consumed as soil evaporation which is often regarded as invalid part of evapotranspiration and thus resulting in the decrease of water use efficiency.     

A characterization model with spatial and temporal resolution for life cycle impact assessment of photochemical precursors in the United States

Background, aim, and scope  Traditional life cycle impact assessment methodologies have used aggregated characterization factors, neglecting spatial and temporal variations in regional impacts like photochemical oxidant formation. This increases the uncertainty of the LCA results and diminishes the ease of decision-making. This study compares four common impact assessment methods, CML2001, Eco-indicator 99, TRACI, and EDIP2003, on their underlying models, spatial and temporal resolution, and the level at which photochemical oxidant impacts are calculated. A new characterization model is proposed that incorporates spatial and temporal differentiation. Materials and methods  A photochemical air quality modeling system (CAMx-MM5-SMOKE) is used to simulate the process of formation, transformation, transport, and removal of photochemical pollutants. Monthly characterization factors for individual US states are calculated at three levels along the cause–effect chain, namely, fate level, human and ecosystem exposure level, and human effect level. Results and discussion  The results indicate that a spatial variability of one order of magnitude and a temporal variability of two orders of magnitude exist in both the fate level and human exposure and effect level characterization factors for NO_x. The summer time characterization factors for NO_x are higher than the winter time factors. However, for anthropogenic VOC, the summer time factors are lower than the winter time in almost half of the states. This is due to the higher emission rates of biogenic VOCs in the summer. The ecosystem exposure factors for NO_x and VOC do not follow a regular pattern and show a spatial variation of about three orders of magnitude. They do not show strong correlation with the human exposure factors. Sensitivity analysis has shown that the effect of meteorology and emission inputs is limited to a factor of three, which is several times smaller than the variation seen in the factors. Conclusions  Uncertainties are introduced in the characterization of photochemical precursors due to a failure to consider the spatial and temporal variations. Seasonal variations in photochemical activity influence the characterization factors more than the location of emissions. The human and ecosystem exposures occur through different mechanisms, and impacts calculated at the fate level based only on ozone concentration are not a good indicator for ecosystem impacts. Recommendations and perspectives  Spatial and temporal differentiation account for fate and transport of the pollutant, and the exposure of and effect on the sensitive human population or ecosystem. Adequate resolution for seasonal and regional processes, like photochemical oxidant formation, is important to reduce the uncertainty in impact assessment and improve decision-making power. An emphasis on incorporating some form of spatial and temporal information within standard LCI databases and using adequately resolved characterization factors will greatly increase the fidelity of a standard LCA. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

菲律宾海脊索动物多样性评估: 基于OBIS数据库

菲律宾海邻近全球生物多样性和进化的中心, 分布着多种重要生物资源。了解本区生物多样性及受威胁物种的分布特征可对掌握其生物多样性现状, 以及未来实施有效的生物多样性保护管理策略提供重要依据。本文利用海洋生物地理信息系统(Ocean Biogeographic Information System, OBIS)数据库, 并参考世界自然保护联盟濒危物种红色名录(IUCN Redlist)的物种濒危程度评估结果, 构建了菲律宾海脊索动物生物多样性和受威胁物种数据库, 结合海洋生态因子特征对该海区脊索动物的物种多样性和不同等级受威胁物种的数量空间分布格局进行了初步分析, 并对脊索动物不同分类阶元生物多样性与生态因子的关系进行了相关性分析。结果表明, 本区海洋脊索动物门已报道11纲56目320科1,171属2,876种。其中在菲律宾海的边缘区域, 特别是菲律宾群岛、台湾岛、日本群岛、马里亚纳群岛及中央的九州-帕劳海脊附近海域, 生物多样性水平相对较高, 而中央海盆区的生物多样性较低。本海域鱼类生物多样性尤其丰富, 共计4纲45目292科1,105属2,768种, 在物种水平上占本区脊索动物物种数的96%。各分类阶元水平的多样性与初级生产力呈显著正相关, 而与水深呈显著负相关。本区脊索动物门受威胁物种共计54种, 其中极危3种、濒危5种、易危22种、近危24种, 分别约占全区脊索动物总种数的0.10%、0.17%、0.76%、0.83%。与本区生物多样性分布格局相似, 受威胁物种多分布于菲律宾海边缘区域, 在中央海脊和深水盆地区域分布较少。本研究表明, 对菲律宾海脊索动物特别是受威胁物种的保护应当以边缘区域优先; 但考虑到当前菲律宾海深海区域生物多样性数据的不足, 也应加强对中央海脊和深水盆地等区域的生物多样性普查。     

基于分布式水文模型的水源涵养不同功能评估方法——以渭河涵养区为例

为了实现水源涵养量计算和不同功能的综合评估,基于分布式水文模型(WEP-L)提出了一种新方法,即利用WEP-L模型计算次降水过程中降水量和地表产流、冠层截留量的差值作为水源涵养量,并分别评估削洪(地表径流量)、补枯(地下径流量)、维持植被生态系统用水(植被蒸腾量)等不同水源涵养功能的评估方法。为了验证该方法的合理性,以渭河流域咸阳站以上区域为例,对比了该方法和InVEST模型方法的计算结果,由于两种方法在评估内容和使用模型上都存在差异,为了保证计算结果的可比性,先对比了基于相同评价内容的WEP-L模型法I和InVEST模型方法,再对比了基于不同评价内容的WEP-L模型法I和WEP-L模型法II,结论如下:基于相同评价内容的WEP模型法I和InVEST模型法计算结果数值接近,研究区2000-2018年水源涵养量年均值分别为12.43 mm(5.76亿m³)和12.08 mm(5.6亿m³),两种方法所得结果空间分布特征相似,稍有差异之处与InVEST模型的参数没有经过本地化处理有关;基于不同评价内容的WEP-L模型法Ⅰ和WEP-L模型法II计算结果数值相差较大,研究区2000-2018年水源涵养量均值分别为12.43 mm和432.57 mm,空间分布特征上有差异的地方分布于研究区的北部、东部及东北部,主要与两种方法评价时是否考虑蒸散发有关。WEP-L模型法II评估结果中削洪、补枯、维持植被生态系统用水等功能多年变化趋势分别为:2006-2010年期间增加、2012年以后下降以及增加。2012年后补枯功能和维持植被生态系统用水功能之间可能存在权衡关系。通过不同方法计算结果差异原因分析,证明了基于WEP-L模型的不同涵养功能评估方法的合理性,其结果也可为渭河涵养区水资源和生态保护策略的制定提供更多依据。     

基于区域城市化LUCC的人类生态过程定量研究——以上海市区典型城市化样带为例

借鉴流域研究的范例,根据上海市1987年、1995年和2003年3期Landsat5 TM遥感影像记录的土地利用／覆被数据和有关的社会经济统计数据,运用Rs和GIS技术在上海市中心西南城市边缘建立典型城市化样带。采用生态足迹法分析该样带内人类的生态供给与需求;提出一城市化区域人类生态过程的新研究方法,得出城市化过程中区域的人类生态质量指数与波动指数,并根据模型计算出的指数值,对样带区域总体及其中城乡区域在城市化中的人类生态状况进行了动态分析,以尝试对区域城市化中人类生态过程进行定量化研究。     

基于MODIS与Landsat 8的艾比湖湿地旱情时空变化及其影响因素分析

对干旱区艾比湖湿地旱情进行多源遥感监测,分析干旱对艾比湖湿地的生态安全与农业生产的影响,为水资源合理配置与干旱预警提供依据。选用2013年5月到2016年5月的MODIS温度和植被指数产品数据反演TVDI指数,并构建二维特征空间,分析土壤水分的时空分布特征,结果表明:TVDI可以有效地反演土壤水分,且精度较高;通过分析,艾比湖湿地土壤水分格局呈现由"极湿润-湿润-正常"面积减少,"干旱-极干旱"面积增加的趋势;在此基础上分析了影响艾比湖干旱变化的影响因素,近年来随着温度升高,风速与蒸发量增加,降水量减少,使艾比湖湿地旱情急剧恶化。利用多源遥感能很好的实现大面积、长时间、高精度的旱情监测,在四年间艾比湖湿地的旱情有所加剧,湖水面积与冰川萎缩变化较为严重,可见艾比湖湿地旱情情况较为不乐观,需加强水资源管理,开展艾比湖旱情监测对于干旱区湖泊生态有重要的理论与实际意义。     

基于元胞自动机的城市空间动态模拟

城市空间动态的模拟与预测可以为城市可持续发展规划与管理提供重要的参考依据。SLEUTH元胞自动机模型在城市空间模拟中较强的适用性和可移植性,该模型通过对历史数据的蒙特卡洛迭代自动寻找城市增长误差最小的参数组合,解决了传统元胞自动机模型中转换规则不易确定的问题。以武汉市为研究案例,运用SLEUTH模型进行了城市空间动态模拟与情景预测。2007年至2011年的城市空间模拟结果显示,模拟结果与实际历史数据可以获得良好的空间匹配度,Lee-Sallee形状指数均在0.6以上,显示SLEUTH元胞自动机模型经过本地化校正后具有较强的适用性和满意的模拟精度。进而,设置了现状趋势、基本保护、严格保护等3种情景对武汉2025年城市空间动态进行了预测,结果显示,各情景模式下城市居住用地均明显增长,农业用地、林地、水域等均有所减少;现状趋势情景和基本保护情景下农田、林地、水域减少的幅度较大,会加剧区域的生境破碎、耕地功能下降、水资源匮乏、湖滨湿地萎缩等生态问题,说明这两种情景不能有效满足城市生态系统健康和可持续发展的需要。严格保护情景下,城市居住用地扩张的程度得到了明显的控制,水域和林地得到了有效的保护,对于重要的自然生态系统组分保护及其服务能力维持可以起到显著作用。