Modeling Runoff Response to Land Cover and Rainfall Spatial Variability in Semi-Arid Watersheds

Hydrologic response is an integrated indicator of watershed condition, and significant changes in land cover may affect the overall health and function of a watershed. This paper describes a procedure for evaluating the effects of land cover change and rainfall spatial variability on watershed response. Two hydrologic models were applied on a small semi-arid watershed; one model is event-based with a one-minute time step (KINEROS), and the second is a continuous model with a daily time step (SWAT). The inputs to the models were derived from Geographic Information System (GIS) theme layers of USGS digital elevation models, the State Soil Geographic Database (STATSGO) and the Landsat-based North American Landscape Characterization classification (NALC) in conjunction with available literature and look up tables. Rainfall data from a network of 10 raingauges and historical stream flow data were used to calibrate runoff depth using the continuous hydrologic model from 1966 to 1974. No calibration was carried out for the event-based model, in which six storms from the same period were used in the calculation of runoff depth and peak runoff. The assumption on which much of this study is based is that land cover change and rainfall spatial variability affect the rainfall-runoff relationships on the watershed. To validate this assumption, simulations were carried out wherein the entire watershed was transformed from the 1972 NALC land cover, which consisted of a mixture of desertscrub and grassland, to a single uniform land cover type such as riparian, forest, oak woodland, mesquite woodland, desertscrub, grassland, urban, agriculture, and barren. This study demonstrates the feasibility of using widely available data sets for parameterizing hydrologic simulation models. The simulation results show that both models were able to characterize the runoff response of the watershed due to changes of land cover.     

A landscape approach to quantifying land cover changes in Yulin, Northwest China

In this study we quantified land cover changes in the arid region of Yulin City, Northwest China between 1985 and 2000 using remote sensing and GIS in conjunction with landscape modeling. Land covers were mapped into 20 categories from multitemporal Landsat TM images. Five landscape indices were calculated from these maps at the land cover patches level. It was found that fallow land decreased by 125,148 ha while grassland and woodland increased by 107,975 and 17,157 ha, respectively. Landscape heterogeneity, dominance and fractal dimension changed little during the 15-year period while landscape became more fragmented, with an index rising from 0.56 to 0.58. The major factors responsible for these changes are identified as the change in the government policy on preserving the environment, continued growth in mining, and urbanization.     

干旱区内陆湖泊流域景观格局变化及其对生态环境的影响

以我国干旱区典型内陆湖泊流域——新疆艾比湖流域为研究区，对其平原区1990--2005年的景观格局动态变化特征进行了研究。结果表明，1990--2005年，研究区农田、湿地及人居地景观的面积增加，其中以农田景观的面积增加量最大；而林地、草地、沙地、戈壁和盐碱地景观的面积呈减少趋势，其中草地、盐碱地和林地景观面积减少较多；各景观类型中以盐碱地、林地、草地和戈壁的转出率较高，而以农田、人居地的转入率较高；研究区景观组份构成没有大的变化，戈壁依然是研究区景观的基质。景观格局变化对区域生态环境的影响主要表现为：农田斑块数量和面积的增加，加大了区域水资源利用压力；林地、草地斑块面积减少，使得平原区绿洲遭受风沙的危害性增大；沙地、戈壁和盐碱地面积减少，使绿洲不同区域生态环境呈现不同变化特征；湿地斑块面积略有增加，对减少艾比湖流域沙尘危害较为有利。     

Land use/land cover change and their effects on landscape patterns in the Yanqi Basin, Xinjiang (China)

Human modification of land use and land cover change (LUCC) drives the change of landscape patterns and limits the availability of products and services for human and livestock. LUCC can undermine environmental health. Thus, this study aimed to develop an understanding of LUCC in the Yanqi Basin, Xinjiang, China, an arid area experiencing dramatic water and land resource use. A time series of satellite images (1964, 1973, 1989, 1999, and 2009) were used to calculate the index of landscape patterns to study the processes involved in changes to land uses and landscape patterns and the influence of this changes on landscape patterns. The results show that land uses in the Yanqi Basin have changed dramatically since 1964 with grassland being mainly converted to cropland. Landscape fragmentation and diversity have decreased in the study area, although landscape fragmentation increased from 1964 to 1999 and then decreased by 2009. The index of landscape diversity decreased from 1.64 in 1964 to 0.71 in 2009. The heterogeneity and complexity of the landscape increased during this period. In contrast, the index of dominance decreased from 0.85 in 1964 to 0.83 in 2009. Land use change drives landscape patterns of the development of the watershed toward diversity and a fragmented structure. Population growth, economic development, and industrial policies were the dominant driving forces behind LUCC in the Yanqi Basin. Sustainable use of land resources is a significant factor in maintaining economic development and environmental protection in this arid inland river basin.     

Cumulative effects of developed road network on woodland—a landscape approach

Population growth, during the twentieth century, has increased demand for new farmlands. Accordingly, road networks have rapidly been developed to facilitate and accelerate human access to the essential resources resulted in extensive land use changes. The present study aims at assessing cumulative effects of developed road network on tree cover of Golestan Province in northern Iran. In order to detect changes over the study period of 1987–2002, the LULC map of the study area was initially prepared from the satellite images of Landsat TM (1987) and ETM+ (2002) using maximum likelihood supervised classification method. Afterwards, a total number of seven landscape matrices were selected to detect cumulative effects of the developed road network on woodland cover. The obtained results indicated that the fragile patches are mainly located at a distance of 171–342 m from the roadside. Furthermore, the majority of the patches affected by cumulative effects of development activities are situated at a distance of 342–684 m from the roadside, over an approximate area of 55 ha. The analysis of landscape metrics revealed that the developed road network has increased the landscape metrics of “the number of patches” and “patches perimeter-area ratio”. It has also followed by a decrease in metrics such as “patches area”, “Euclidean nearest neighbor distance”, “patches proximity”, “shape index”, “contiguity”, and “mean patches fractal dimension”. The road network has also increased the “number of patches” and decreased the “mean patches area” representing further fragmentation of the landscape. With identification of highly affected wooldland cover patches, it would be possible to apply adaptive environmental management strategies to preserve and rehabilitate high-priority patches.     

Supplementing Land-Use Statistics with Landscape Metrics: Some Methodological Considerations

Landscape monitoring usually relies on land-use statistics whichreflect the share of land-sue/land cover types. In order tounderstand the functioning of landscapes, landscape pattern mustbe considered as well. Indicators which address the spatialconfiguration of landscapes are therefore needed. Thesuitability of landscape metrics, which are computed from thetype, geometry and arrangement of patches, is examined. Two casestudies in a surface mining region show that landscape metricscapture landscape structure but are highly dependent on the datamodel and on the methods of data analysis. For landscape metricsto become part of policy-relevant sets of environmentalindicators, standardised procedures for their computation fromremote sensing images must be developed.     

基于遥感和Markov模型的新疆生产建设兵团土地利用变化

通过对兵团土地利用空间格局变化分析,选择合适的土地利用政策保护生态环境。运用RS和GIS技术对兵团近10年土地利用/覆被变化及景观格局空间变化进行分析,并在此基础上运用Markov模型对未来30年土地利用变化进行预测。2000—2010年,新疆生产建设兵团景观多样性升高,连通性增强,形状愈来愈简单,景观格局整体变化不大;草地、灌丛、湿地、荒漠和冰川/永久积雪面积减少,耕地和城镇面积增加,森林保持稳定;人为干扰对土地利用结构的变化具有重要作用,土地利用强度受人为活动影响的同时受土地利用政策影响;在未来30年间耕地和城镇面积继续增加,除森林基本保持不变外其他土地利用类型均减小。兵团城镇用地与草地和耕地之间的矛盾逐渐显现,势必引起兵团生态格局的变化。因此,必须实行合适的土地利用政策保护环境。     

Desert disturbance assessments of regional oil exploitation by Aster and ETM+ images in Taklimakan Desert China

To feed its rapidly growing energy demand, oil exploitation in China has never been more intensive. The most obvious characteristics of oil exploitation are progressive and regional, which can be monitored by remote sensing, such as land use and cover change, either perpetual or temporary, during oil field development such as construction of oil well, roads, transportation systems and other facilities. In this paper, the oil field located on the north edge of Taklimakan Desert, in the Tarim River watershed in northwest of China. The disturbance effects of regional oil exploitation were the main content of regional environmental managements and monitoring. Based on Enhanced Thematic Mapper Plus (ETM+) and Aster images, analyzed regional land use and landscape change from 2001 to 2003. By the comparison, it can be concluded that the ecological quality was deteriorating in these 3 years. The woodland was degrading to grass and dessert. The area of woodland dropped from 9.06 km(2) in 2001 to 3.24 km(2) in 2003 with a 64.23% decrease. At the same time, the area of shrubbery lessened 18.23%. On the other hand, the whole area of dessert and Saline soils inflated from 15.08 km(2) in 2001 to 25.36 km(2) in 2003. The patch number of bare land did climb dramatically, but single patch area increased. The research demonstrated that dessert and Saline soils patches were activated by the human behavior and climate change. The information from the ETM+ and Aster images was proved be an effective and efficient way to be applied in regional environmental managements.     

Landscape connectivity changes analysis for monitoring desertification of Minqin county, China

Landscape connectivity, as an important indicator of regional landscape functional pattern measured by cost–distances model, could both reveal evidence of, and act as an indicator, for desertification. Using Minqin county as a case study, this study was further to test cost–distance connectivity for indicating desertification, and to analyze temporal changes of connectivity in the county from 1977 to 1997. The results further indicate the connectivity interpreted as lower cost–distance and higher risk of desertification. The temporal change analysis of connectivity provides more detail supplement of desertification processes. Landscape connectivity changes in the county had three distinctive phases, the strongest decline of log cost–distance with overwhelming decrease area and decrease amount in the period 1977–1984, and its slight decline with the relative balance between the high decrease amount and high increase amount in the period 1984–1992, then its the slight decline with the relative balance between the low decrease amount and low increase amount in the period 1992–1997. The frequent temporal and spatial transition in source class, grassland, alkali–saline land and irrigated cultivated land caused negative effects on the oasis environment.     

平顶山地区景观格局动态特征及驱动力分析

以平顶山地区为研究对象,利用平顶山地区1992年Landsat-TM影像和2006年中巴资源卫星遥感影像,运用景观生态学原理,借助遥感和GIS技术,选取景观多样性、景观优势度、景观均匀度、景观破碎度等指标指数进行分析,揭示平顶山地区近14 a来城市景观格局演变及其驱动力。研究结果表明:交通用地、工矿及居民点和耕地用地显著增加,林地、水域显著减少;除工矿及居民点外,该地区各类型斑块数量均有增加,其中林地增加最为显著;交通用地、工矿及居民点的破碎度降低,水域、林地、耕地的景观类型破碎度增高;耕地的分维数、形状指数呈下降趋势,而林地的分维数和形状指数呈上升趋势;平顶山地区景观多样性和均匀度都呈下降趋势,而优势度和破碎度增加;景观格局变化受人为因素影响较大,人口增加、经济发展、城镇化和工业发展是平顶山地区景观格局演变的主要驱动力。