黑河流域2001~2017年植被变化特征及其可延续性评价

植被的变化特征是流域生态监测的重要内容和流域综合管理决策的基础信息。基于谷歌地球引擎(Google Earth Engine,GEE),利用空间分辨率为250 m的MODIS-EVI(Enhanced Vegetation Index)产品,研究2001~2017年黑河流域植被的时空变化趋势及延续性特征。结合气温、降水与河流径流量观测数据,分析黑河流域上游、中下游绿洲与非绿洲区植被变化的影响因素。结果表明:近17年来黑河流域植被年最大EVI值年均增幅为0.0039,年均新增植被面积为480.3 km^2。受气温、降水、耕地开垦、水资源管理措施及与其密切相关的地下水等因素的不同影响,上中下游表现出不同的变化特征。无论是年最大EVI值还是植被面积,中游的增加趋势最为显著,绿洲区较非绿洲区增加趋势更为明显。这种变化趋势短期内可能延续,但长时间内存在较大风险。研究为快速监测植被变化提供了示范,揭示了干旱区植被监测中长势变化与类型变化的同等重要性,流域植被变化的区域协同性对合理分水、加强地表-地下水协同管理等流域综合管理提出了更高要求。     

利用MODIS植被指数评估分水对黑河中游的影响

为缓解黑河下游额济纳旗生态恶化的现状,国家对黑河流域实施了分水政策。在下游环境得到了充分改善的同时,中游绿洲地区的发展却受到了不同程度的限制。利用2000~2004年的MODIS归一化植被指数数据,对中游两个绿洲地区连续5 a生长季的植被覆盖面积进行监测。分析并对比其植被覆盖面积的增长趋势,对黑河流域中游地区受分水影响的程度做出评估。     

Relating vegetation dynamics to temperature and precipitation at monthly and annual timescales in Taiwan using MODIS vegetation indices

To predict the responses of the timing, duration, and density of photosynthetically active plant cover to a changing climate, it is necessary to first quantitatively describe the relationships between temporal and spatial patterns of vegetation cover and both spatial and inter-annual variation in temperature and precipitation. We examined these relationships at multiple scales in Taiwan using monthly maximum composite values of MODIS-NDVI and MODIS-EVI between 2000 and 2012. The two vegetation indices were highly correlated to each other on a monthly basis for non-forest land-cover types, but correlated poorly in forests, probably due to the saturation of NDVI. However, the two indices were equally sensitive in detecting the onset and offset of growing season for all vegetation types. We found that EVI was positively related to both precipitation and temperature on a monthly timescale, although the relationships were not significant at the annual timescale. The much greater variation in monthly than in annual precipitation and temperature probably explains this difference. At low elevations, precipitation had a positive effect and temperature had a negative effect on EVI; however, at high elevations, which are mostly forested, both were positively related to EVI (although precipitation effects were not significant). We interpret this as evidence of water limitation of photosynthetic cover in the warmer, low-elevation parts of the island, whereas in the higher-elevation areas precipitation was usually adequate to satisfy evapotranspirative demand. This study illustrates the importance of examining the effects of precipitation and temperature on plant growth at a range of spatial and temporal scales. Specifically, finer spatial and temporal scales of analysis may better reveal climatic controls over vegetation growth than broader scales of analysis.     

Drought and elevation effects on MODIS vegetation indices in northern Arizona ecosystems

Northern Arizona ecosystems are particularly sensitive to plant-available moisture and have experienced a severe drought with considerable impacts on ecosystems from desert shrub and grasslands to pinyon-juniper and conifer forests. Long-term time-series from the Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI) are used to monitor recent regional vegetation activity and temporal patterns across various ecosystems. Surface air temperature, solar radiation and precipitation are used to represent meteorological anomalies and to investigate associated impacts on vegetation greenness. Vegetation index anomalies in the northern Arizona ecosystem have a decreasing trend with increasing surface air temperature and decreasing precipitation. MODIS NDVI and EVI anomalies are likely sensitive to the amount of rainfall for northern Arizona ecosystem conditions, whereas inter-annual variability of surface air temperature accounts for MODIS NDVI anomaly variation. The higher elevation area shows the slow vegetation recovery through trend analysis from MODIS vegetation indices for 2000–2011 within the study domain and along elevation.     

高分辨率遥感影像GeoEye-1在黑河下游柽柳生物量估算中的应用

以黑河下游绿洲柽柳为研究对象,利用高分辨率遥感影像GeoEye-1柽柳分类结果,基于典型样点生物学特性调查与生物量试验,建立柽柳冠幅面积与生物量关系模型,计算研究区柽柳地上部分的生物量,分析黑河0~2、2~5、5~10与10~15 km不同缓冲带柽柳生物量空间分布规律。结果显示:研究区柽柳总生物量为4.10×10⁵ t,其中:0~2、2~5、5~10与10~15 km缓冲带内柽柳生物量分别为2.34×10⁵、1.07×10⁵、6.35×10⁴和5.17×10³ t。河流距离对柽柳生物量影响显著,单位面积柽柳生物量随着与河流距离的增加而减少,二者相关系数为-0.97。     

基于遥感的黑河流域植被物候空间格局提取分析

植被物候的检测对于认识自然季节现象的变化规律,服务农作物生产、全球变化、生态学应用方面具有重要价值。植被指数是描述植被数量、质量、植被长势和生物量指标的重要参数。利用SPOT VEGETATION NDVI时间序列数据,采用Savitzky-Golay滤波方法重建了NDVI的年内变化序列,并利用此数据提取了黑河流域植被物候空间分布格局。结果表明,采用此方法得到的植被物候信息和该区域的农事历信息符合较好。黑河流域植被物候具有明显的空间格局。上游的高寒草地区生长季长度较短。中游地区受人类活动影响严重,较为符合该区农作物生长信息。     

街口水文站自动监测系统设计与建设

针对新安江洪水流速大、涨落快等特点,以及街口断面水位变幅大、漂浮物多等特性,组合应用多种监测设备和软件系统,建设街口水文站自动监测系统,以实现不同的水位级和水情条件下雨量、水位、流量和泥沙含量数据的实时在线自动采集,传输,计算处理及入库管理。街口水文站自动监测系统可为新安江流域水资源管理、水量分配、生态流量管控提供基础数据支撑,亦可为山区性大江大河自动监测系统建设提供参考和借鉴。     

Mapping the potential annual total nitrogen load in the river basins of Japan with remotely sensed imagery

The increase of nutrient loads such as nitrogen and phosphorus to a river due to land cover changes in surrounding areas has been one of the major sources of water pollution or eutrophication. Monitoring the influent nutrient load from river basins to rivers is now crucial in the management of river basin environments. The monitoring is not easy, however, because it requires spatial and temporal measurement tools for land cover changes in the river basin and water qualities, and also it requires models relating them.In this study, we first analyzed the relation between the land cover types estimated from monthly maximum Normalized Difference Vegetation Index (NDVI) imagery calculated from NOAA Advanced Very High Resolution Radiometer (AVHRR) imagery and the annual total nitrogen load discharged from river basins. We found that the runoff load factor from urban areas is higher than those of forested areas. We also found that the impacts of land cover such as plantation and field weed communities on the total nitrogen load of each river are higher than the impacts of other land cover types such as Beech and Camellia japonica community type.Finally, we produced two advanced maps of the potential annual total nitrogen load (PTNL) index and the potential annual total nitrogen load for each river basin area (PTNL/area) index by considering the relationship between the land cover types and the annual total nitrogen load discharged from river basins in Japan. The PTNL map will be useful for the risk assessment of total nitrogen load impact on lakes and the sea through rivers from each basin. The PTNL/area index, which considers the effects of river basin areas, will allow evaluation of the state of river basins.     

沂蒙山区植被NDVI的时空特征及其对水热条件的响应

植被是生态环境变化的综合指示器,研究其对水热条件的响应已成为当前气候变化研究中的主要内容之一。选取北方土石山区典型代表--沂蒙山区为研究对象,基于沂蒙山区1980~2010年的气温、降水和2001~2010年MODIS\|NDVI数据,结合相关分析和最小二乘法,定量分析该区植被指数的年际、年内的时空变化及其对水热条件的响应。结果表明:①近10 a沂蒙山区NDVI max的变化斜率为0.0026;②植被显著退化区和良好区分别占研究区总面积的10.52%和28.62%;③不同季节(主要是春、夏和秋季)植被状况均呈现良性发展趋势;④台站数据显示植被年际变化与年降水和年均气温的关系并不密切,而在月时间尺度上植被与气温的相关性要强于与降水的相关性。综上所述,沂蒙山区植被状况总体呈良性发展趋势,气温可能是影响该区植被生长的主导因子。     

Modelling gross primary production in the Heihe river basin and uncertainty analysis

Accurate and timely monitoring of gross primary production (GPP) at regional and global scales is necessary for understanding the terrestrial biosphere carbon balance. In this article, 8-day composite GPP is estimated using the region production efficiency model (REG-PEM) in the Heihe river basin from 2006 to 2008. The result indicates that GPP meets the seasonal cycle well and varies with different land covers. Analysis of uncertainty and sensitivity of the REG-PEM model are implemented by the Monte Carlo method. GPP is simulated with a test data set; the data set includes three groups, and each group has 8000 points. The three groups obey uniform distribution, normal distribution and beta distribution, respectively. Uncertainty is assessed by the quantification of mean values and standard deviation of outputs. The distribution of simulated GPP is slightly different from that of model-calculated GPP over the study sites. Among the input parameters, the land surface water index (LSWI) and air temperature (T) make less of a contribution to model output than photosynthetic active radiation (PAR) and the enhanced vegetation index (EVI). The main sources of model uncertainty are input data uncertainty and uncertainty from the specific model.     

Global interannual variability in terrestrial ecosystems: sources and spatial distribution using MODIS-derived vegetation indices,social and biophysical factors

Variations in global vegetation activity were measured at a global scale, from 2000 to 2006, based on the Enhanced Vegetation Index (EVI) extracted from the 1km resolution Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data. Interannual variations in phenology and/or in annual integrated vegetation index are mapped using change metrics. The relationships between interannual variability and climate, ecosystem disturbances and land use are also examined. Around 14% of the study area experienced high interannual variability in land surface attributes over the six years. The ecosystems most subjected to large fluctuations in surface conditions were the boreal ecosystems, temperate ecozones, and subtropical and tropical steppes. These changes were largely related to rainfall variability and were associated with mean annual rainfall, agriculture, fire regimes and population density. Large population concentrations were mostly found in more stable ecozones. Rainfall and natural fire regimes explained more than half of the land surface variability in Australia. An additional global analysis on trends in vegetation activity also shows that around 4.5% of the vegetated surface of the Earth, excluding deserts and frequently cloudy regions, experienced a continuous decrease in vegetation activity over the six years. This represents more than twice the area experiencing a greening trend over this time period and concerns mostly tropical, subtropical and temperate forest ecozones. The total change in vegetation activity at a global scale and per year amounted to –2% of the annual integrated EVI aggregated across all ecosystems of the study area, on average for the years 2001–2006.     

Retrieval of Component Temperatures based on Landsat-7 ETM+ Remote Sensing Data

Land surface temperature plays an important role in drought monitoring and Simulation of surface heat flux.In arid and semi\|arid regions,the Two\|Source Energy Balance model (TSEB) is commonly used to calculate the heat flux of the earth’s surface.Taking the typical irrigated area of the middle reaches of Heihe as the research area,the four Landsat\|7 ETM+ remote sensing images are selected.The soil surface temperature and canopy temperature were retrieved by combining vegetation index with TSEB model.The decomposition algorithm of soil surface temperature and vegetation canopy temperature is mainly discussed.The results showed that soil surface temperature and vegetation canopy temperature had good temporal and spatial consistency.The inversion accuracy of soil surface temperature and vegetation canopy temperature is indirectly verified by surface net radiation and surface heat flux.The calculated values of surface net radiation and surface heat flux correlate well with the observed values,and the correlation coefficient is greater than 0.92.The linear regression analysis of surface net radiation and surface heat flux shows that the fitting accuracy is high.The soil surface temperature and canopy temperature obtained by surface temperature decomposition are feasible for monitoring drought in typical areas and simulating surface heat flux.     

利用长时间序列Landsat分析博斯腾湖面积变化

目的 近年来博斯腾湖面积波动较大,影响当地经济发展,掌握博斯腾湖面积变化及其与气候变化的相关规律,以指导湖泊保护和可持续利用管理策略。方法 利用Landsat影像计算1988—2014年博斯腾湖面积,监测并分析湖水面积年际变化及空间变化趋势,探讨博斯腾湖流域年降水量、年均气温变化和人类活动对湖水面积的影响,并将监测结果与MODIS数据计算的2000—2014年湖水面积以及1987—2011年实测水位数据进行对比验证。结果 结果表明,以2002年为分界线,博斯腾湖面积变化分2个阶段:1)1988—2002年,湖水面积呈增加趋势,增加288.88 km²,增长了31.62%;2)2002—2014年呈减小趋势,减小281.56 km²,减少了23.42%。根据气候条件分布差异,将博斯腾湖流域分为山区和平原区,分析发现:1988—2002年,山区年降水量和气温上升,与湖水面积呈显著正相关;2002年后,山区年降水量相对下降,平原区气温升高,人类活动用水量增加。结论 湖水面积变化受流域气候与人类活动共同作用,1988—2002年主要受山区气候影响,2002年后湖水面积缩小可能是气温升高和人类活动用水量增加导致。     

Snow Cover Variation and Meteorological Factor Researchin Yarlung Zangbo Basin of Tibet from 2002 to 2015

The snow cover variation in Yarlung Zangbo from July 2002 to April 2015，as the mother river of Tibet，has been analyzed in this article.The hydrological year is from September of the year to August of the next year.The snow cover variation was studied used by cloudless snow cover data at 500 m and surface temperature from MODIS，digital elevation model (DEM) and meteorological data.The relationship was established between surface temperature from MODIS and major meteorological factors.The results show that the average snow cover in the study area is 3.56× 10⁴km² in the past 12 years，showing an overall decreasing trend.The area with large snow cover is in the upper and lower reaches of the basin，and the stable and seasonal snow dominate the rural area in the middle reaches and valley basins，with perennial less snow distribution.The stability of snow and perennial snow distribution is more than 4 000 meters above the sea level，which the snow lasts for more than 180 days.And the seasonal snow is mainly less than 4 000 meters above sea level with large variation of snow cover in the area.The inversely relationship is between the air temperature and the area of snow cover，but not significant between the precipitation and the area of snow cover.And the correlation in the surface temperature and the area of snow cover is obvious.In Short，the rising temperature is the main driving factor of snow area reduction in the basin.     

Large-scale monitoring of snow cover and runoff simulation in Himalayan river basins using remote sensing

Various remote sensing products are used to identify spatial-temporal trends in snow cover in river basins originating in the Himalayas and adjacent Tibetan-Qinghai plateau. It is shown that remote sensing allows detection of spatial-temporal patterns of snow cover across large areas in inaccessible terrain, providing useful information on a critical component of the hydrological cycle. Results show large variation in snow cover between years while an increasing trend from west to east is observed. Of all river basins the Indus basin is, for its water resources, most dependent on snow and ice melt and large parts are snow covered for prolonged periods of the year. A significant negative winter snow cover trend was identified for the upper Indus basin. For this basin a hydrological model is used and forced with remotely sensed derived precipitation and snow cover. The model is calibrated using daily discharges from 2000 to 2005 and stream flow in the upper Indus basin can be predicted with a high degree of accuracy. From the analysis it is concluded that there are indications that regional warming is affecting the hydrology of the upper Indus basin due to accelerated glacial melting during the simulation period. This warming may be associated with global changes in air temperature resulting from anthropogenic forcings. This conclusion is primarily based on the observation that the average annual precipitation over a five year period is less than the observed stream flow and supported by positive temperature trends in all seasons.     

地表通量对模型参数的不确定性和敏感性分析

基于2007年12月22日~2009年12月31日黑河流域阿柔冻融观测站的气象驱动数据,利用通用陆面模型(Common Land Model,CoLM)模拟的地表通量结果,研究地表通量对模型参数(叶面积指数、地表反照率和植被覆盖度)的不确定性与敏感性。结果表明,叶面积指数、地表反照率和植被覆盖度对地表感热和潜热通量不同组分的影响存在较大的差异。其中,植被层的感热和潜热通量对叶面积指数的敏感性程度较高,敏感系数均达到0.7以上;与潜热通量相比,感热通量对反照率更加敏感,土壤感热、植被感热和总感热通量对反照率的敏感系数分别达到-0.96、-0.97和-0.66,而土壤潜热和总潜热通量对地表反照率的敏感系数仅为0.1左右;植被潜热通量对植被覆盖度的敏感性程度很高,敏感系数范围为0.92~0.96,而土壤感热通量对植被覆盖度最不敏感,敏感系数只有0.18左右。     

Evapotranspiration estimation in the Yellow River Basin,China using integrated NDVI data

It is important to estimate land surface evapotranspiration (ET) for water resources evaluation, drought monitoring and crop production simulation. In this paper, a relationship between annual ET, integrated Advanced Very High Resolution Radiometer (AVHRR) Normalized Difference Vegetation Index (NDVI) and Relative Moisture Index (RMI) was established. Based on this relationship, the spatial distribution and dynamic change of annual ET were estimated for the Yellow River Basin, China from 1982 to 2000. Our analyses involved the use of integrated NDVI data, monthly mean air temperature, and precipitation. Our results showed that the integrated AVHRR NDVI can be used to effectively estimate annual ET in the Yellow River Basin, with an accuracy over 90% for the whole basin.     

黑河流域下游天然植被生态需水预测

根据对黑河下游天然植被生态状况的分忻，对不同水平年提出了5个生态恢复方案，计算预测了各方案的生态需水量．提出了推荐生态恢复方案。     

Landscape changes of the Ejin Delta in the Heihe River Basin in Northwest China from 1930 to 2010

The Heihe River Basin is located in the arid and semi-arid region of Northwest China; during the past 80 years, this basin has experienced water resource competition between irrigation agriculture and ecological demand in its middle and lower reaches, respectively. The land cover of the Ejin Delta in the lower reaches of the Heihe River Basin was interpreted and analysed for four different periods using a map created by Dr Sven Hedin in the 1930s, Corona satellite images taken in 1961, and Landsat Thematic Mapper (TM) images taken in 2000 and 2010. Overall, the results show that (1) the coarse resolution of the 1930s map increased the uncertainty of analysis in the study area and (2) the river area in the Ejin Delta decreased by 91.0% from the 1930s to 2000. In addition, two major terminal lakes, Gaxun Nuur Lake and Sogo Nuur Lake, dried up in 1961 and 1992, respectively, and the area of Populus euphratica decreased by 76.1% from the 1930s to 2000. Most reeds were overtaken by shrubs between the 1930s and 1961, which caused the area of reeds to decrease from 3481 to 1332 km² and the area of shrubs to increase from 805 to 2795 km². From the 1930s to 2000, the desert and alkaline land areas increased by 42.2% and 52.4%, respectively. (3) After the water transfer project was implemented in 2000, the area of Sogo Nuur Lake recovered to 40.58 km² by 2010. The areas of Populus euphratica, shrubland, and reedland showed a recovering trend, with increases of 4.5%, 6.5%, and 43.5%, respectively, by 2010. The desert and alkaline land areas decreased by 4.2% and 15.2%, respectively, by 2010. The area of cultivated land increased from 25 km² in 1961 to 85 km² in 2000 and rapidly approached 160 km² in 2010. These changes over time indicated that the ecological habitat in the Ejin Delta deteriorated between the 1930s and 2000. However, the water transfer project effectively changed the degradation trend.     

黑河流域湿地、农田、草地生态系统碳通量变化特征及驱动因子分析

为了认识黑河流域湿地、农田、草地生态系统不同时间尺度的碳通量特征及与环境因子的关系,并为干旱区生态系统碳源/汇效应评估提供理论依据.采用涡度相关技术对黑河流域湿地、农田、草地生态系统进行长达7 a的碳通量、气象因子观测,分析了净生态系统生产力(NEP)、生态系统呼吸(Reco)、总初级生产力(GPP)在日际、季节、年际...