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1.
Based on the Landsat TM data in 1988 and 2002, the GIS technique and Fragstats software were used to calculate the land use conversion matrix and eight landscape metrics at landscape and patch class levels in upstream, midstream, and downstream regions of Nenjiang River basin. The characteristics of land use and landscape pattern changes in each region during 1988–2002 were analyzed. The results show the followings: 1) During the period from 1988 to 2002, farmland and construction land area increased, while the areas of forestland, grassland, and unutilized land decreased in all three regions. The conversion trends from forestland and grassland to farmland were obvious. The conversion from forestland to farmland mainly occurred in the upstream region, whereas the conversion from grassland to farmland primarily occurred in the midstream and downstream regions. 2) The water area in the upstream and midstream regions enlarged, mainly due to the increase of water impounded area as a result of the construction of reservoirs. Comparatively, the water area in the downstream region decreased, and it mainly occurred in the east part of downstream region with concentrated lakes and swamps. 3) The degree of landscape fragmentation increased in each region. The controlling ability of forestland was weakened, and its patch shape became more complicated. In contrast, the controlling ability of farmland was reinforced, and the connectivity among patches increased. 4) The landscape pattern shows some gradient features. From the upstream to downstream regions, the disturbance of human activities on dominant patches was intensified, and consequently, the landscape fragmentation extent and heterogeneity were enhanced.  相似文献   

2.
Landscape metrics are important when studying landscape structure and function. This study investigated the sensitivity of two core sets of landscape metrics to different land use classification systems by analyzing two typical landscapes at a small watershed scale and a county scale on the Loess Plateau, China. The results showed that (1) eight landscape metrics, selected using Spearman’s correlation coefficient method and principle component analysis, adequately reflected the major landscape properties at both scales. (2) Land use classification had a significant influence on most of the selected landscape metrics, affecting their magnitude and the way in which they changed with increasing classification details; four general patterns were exhibited, i.e., increasing; decreasing; increasing and then decreasing; and relatively constant at the small watershed scale, while for the county scale, they were increasing; decreasing; increasing and then decreasing; and remaining relatively constant after initially increasing. (3) The general response patterns of most of the selected landscape metrics to the changing land use classification were similar among different years at both scales, which implied that the age of the data source used to generate the land use maps since 1982 had little effect on the landscape metrics, and that the underlying landscape pattern described by the metrics had not notably changed.  相似文献   

3.
The mechanism of interaction between land use change and landscape pattern is pivotal in research concerning global environmental change. Quantitative evaluation of land use change that has resulted from excessive land development and its impact on landscape pattern are important for sustainable utilization of local land resources. The study area was the Manas River watershed, a typical watershed in an arid area. The present study evaluated the influence of long-term land use change on the landscape pattern; the findings are valuable for economic development and environmental protection. The processes for land use change and changes in landscape pattern were reconstructed and analyzed for data in topographic maps dated 1962 and in remote sensing images taken in 1976, 1989, 1999 and 2008 using mathematical models and landscape metrics. The results indicate significant changes in land use over the past 50 years, with increases in the areas of cultivated land and construction land, and a significant decrease in unused land and woodland areas; grassland and water resources first increased and then tended to decrease over this time. The comprehensive index of land use change is 0.55, indicating an unbalanced, one-way transition in the study area. Landscape fragmentation and diversity increased and landscape dominance decreased; in other words, differences between landscapes decreased. The changes resulted in a significant tendency toward diversity and fragmentation of the landscape. Therefore, large-scale intensive agricultural development can reduce the negative influence of land use change on the landscape pattern.  相似文献   

4.
根据陇东黄土高塬沟壑区典型小流域——南小河沟流域1954—2014年实测降雨产沙资料,应用降雨侵蚀力偏差系数法研究不同土地利用类型及空间尺度下侵蚀产沙的雨量阈值、雨强阈值及复合阈值标准,并通过对比分析确定了最优降雨阈值标准。结果表明:① 对于林地和草地坡面小区,其雨量阈值标准平均值（21.0 mm）较裸地（8.7 mm）和农地（9.7 mm）坡面小区分别提高了141%和116%,植被措施能够显著提高降雨阈值标准。② 杨家沟林地小流域的雨量阈值标准为16.5 mm,低于布设在该流域的林地坡面小区,同时对比董庄沟草地小流域及其坡面和全坡面小区的雨量阈值标准,其大小亦为:草地坡面尺度 > 草地全坡面尺度 > 草地小流域尺度,由此可见,降雨阈值标准会随着空间尺度增大而减小。③ 降雨阈值标准综合评价结果表明,各样点最优降雨阈值标准均为P≥a或I30≥b这一复合因子标准,而在降雨单因子阈值标准中,对于农耕地和裸地坡面小区,宜采用最大30 min雨强（I30）标准;对于经过水土流失治理的下垫面,宜采用雨量（P）标准。该研究可为区域土壤侵蚀预报提供参考。  相似文献   

5.
Although rapid land-use change has taken place in many arid and semi-arid regions of northwestern China, relatively less attention has been paid to studying the characteristics of land use change, as well as the ecological responses of land use change in these regions, especially in fragile agro-pastoral regions. This paper analyzes the land use change and its ecological responses during 1985–2005 based on the landscape metrics change and transition matrix of land use types by the combined use of satellite remote sensing and geographical information systems in Shandan County, a typical agro-pastoral region in the middle and upper reaches of Heihe River, northwest China. The results indicate significant changes in land use have occurred and the landscape has become more continuous, clumped and more homogeneous within the examined area. Land use change was mainly characterized by remarkable expansion of barred land and water area, slight increase of cropland and urbanized land, and evident shrinkage of grassland and woodland. The study also demonstrates that the land cover suffered severe degeneration and the ecological environment tended to deteriorate over the study period, mainly as follows: grassland degradation, land desertification and ecosystem services decline.  相似文献   

6.
Xiaojiang watershed is a typical karst agricultural region of Yunan Province, China. A case study of land-use changes documents changes of soil properties from 1982 to 2003. The results are as follows: (1) The total land use transformed covers 610.12 km2, of which land use changed from unused land into cultivated land and forestland, and forestland into cultivated land during the past 20 years in Xiaojiang watershed. (2) The rapid growth of population and economic development were the main driving forces of cultivated land increase. (3) Soil properties showed modification owing to different land-use changes. The contents of the soil organic matter, total nitrogen, and total phosphorus in 2003 were significantly lower than that in 1982 after the forestland and unused land were transformed into the cultivated land, but the soil pH increased significantly in 2003. Organic matter, total nitrogen, and total phosphorus for shorter-time reforestation land declined, but the pH increased. Soil properties have improved significantly after cropland was transformed into orchard land. The organic matter, total nitrogen, total phosphorus, available nitrogen, and available phosphorus declined significantly, but pH increased significantly after rock desertification.  相似文献   

7.
石羊河流域及其典型绿洲景观动态变化研究   总被引：9，自引：0，他引：9  
根据1986年和2000年的TM影像数据,利用GIS技术和景观结构分析软件FRAGSTATS,分别在类型和景观两个水平上分析了石羊河流域及武威和民勤两个典型绿洲近15a来的景观结构变化.结果表明:在整个流域水平上,虽然发生了景观结构的空间变化,但总体上相对稳定.在典型绿洲区,特别是民勤绿洲景观格局的变化较大,表现为景观的破碎化,形状的简单化和景观多样性的降低,以及耕地、沙地的增加和林地、草地的显著减少,沙漠化趋势加剧.  相似文献   

8.
Watershed land use can affect submerged aquatic vegetation (SAV) by elevating nutrient and sediment loading to estuaries. We analyzed the effects of watershed use and estuarine characteristics on the spatial variation of SAV abundance among 101 shallow subestuaries of Chesapeake Bay during 1984–2003. Areas of these subestuaries range from 0.1 to 101 km2, and their associated local watershed areas range from 6 to 1664 km2. Watershed land cover ranges from 6% to 81% forest, 1% to 64% cropland, 2% to 38% grassland, and 0.3% to 89% developed land. Landscape analyses were applied to develop a number of subestuary metrics (such as subestuary area, mouth width, elongation ratio, fractal dimension of shoreline, and the ratio of local watershed area to subestuary area) and watershed metrics (such as watershed area). Using mapped data from aerial SAV surveys, we calculated SAV coverage for each subestuary in each year during 1984–2003 as a proportion of potential SAV habitat (the area < 2 m deep). The variation in SAV abundance among subestuaries was strongly linked with subestuary and watershed characteristics. A regression tree model indicated that 60% of the variance in SAV abundance could be explained by subestuary fractal dimension, mean tidal range, local watershed dominant land cover, watershed to subestuary area ratio, and mean wave height. Similar explanatory powers were found in wet and dry years, but different independent variables were used. Repeated measures ANOVA with multiple-mean comparison showed that SAV abundance declined with the dominant watershed land cover in the order: forested, mixed-undisturbed, or mixed-developed > mixed-agricultural > agricultural > developed. Change-point analyses indicated strong threshold responses of SAV abundance to point source total nitrogen and phosphorus inputs, the ratio of local watershed area to subestuary area, and septic system density in the local watershed.  相似文献   

9.
采用新疆喀什噶尔河流域1990、2000和2010年的Landsat-TM影像数据和中巴资源卫星数据, 结合GIS技术, 分析了喀什噶尔河流域近20 a土地利用/覆被及景观格局动态变化特征, 并对其变化原因进行探讨. 结果显示: 在1990-2010年喀什噶尔河流域耕地、建设用地、盐碱地、水域湿地、裸土地和其他未利用地面积呈不断增加趋势, 变化幅度分别为73.92%、51.44%、24.27%、10.24%、6.47%和2.98%; 林地、草地和沙地面积减少, 变化幅度分别为-4.13%、-17.16%和-0.73%; 裸石岩砾面积近20 a基本维持不变. 利用转移矩阵可知, 流域新增耕地面积主要来自于16.46%的草地和3.36%的林地; 新增建设用地主要来自于1.46%的耕地和0.22%的草地; 新增水域湿地面积主要来自于0.18%的草地; 新增盐碱地面积主要来自于0.28%的草地. 1990-2010年的20 a里喀什噶尔河流域耕地和水域湿地分布趋于集中, 景观优势度增强, 且斑块之间的联系不断增强. 林地和草地面积减少, 景观趋于破碎化, 景观优势度降低. 喀什噶尔河流域土地利用类型及景观指数的变化受人口、经济、政策和技术的多重影响, 导致流域耕地面积增加、植被退化. 因此, 合理利用流域水土资源对流域生态环境安全十分重要.  相似文献   

10.
Ecological restorations over time may have profound effects on ecological and socio-economic systems. However, land-use changes and landscape functions that accompany ecological restorations can have spatial differentiations due to varied biophysical and socio-economic contexts. Therefore, these spatial differentiations caused by ecological restoration must be understood for better planning and management of restoration activities. The Baota District, with 576 villages in the center of the Chinese Loess Plateau, was selected as the study area because of its dramatic transition from cropland to grassland and shrubland from 1990 to 2010. Using the ArcGIS software and a k-means clustering analysis, an approach to identify types of land-use change patterns (TLCPs) at the village level was developed, and four TLCPs were delineated. The analysis indicated a general pattern of cropland decline by 21.6 %, but revealed significant spatial variations between villages in different TLCPs. Vegetation cover and soil retention, which are key proxies for landscape functions, increased by 22.70 and 108 %, respectively, from 2000 to 2010 with significant spatial heterogeneity. The Universal Soil Loss Equation was employed for the assessment of soil retention. The analysis of landscape metrics revealed a major trend of fragmentation and regularity on the county and village scale; however, spatial variations remained. Physical attributes were used to characterize different TLCPs, and notable differences were found. The spatial heterogeneous change in land use and landscape functions on the village scale may be useful for land use and ecological restoration management policy makers.  相似文献   

11.
Rapid land-use change has taken place in many arid and semi-arid regions of China over the last decade as the result of demand for food for its growing population. The Heihe River Basin, a typical inland river basin of temperate arid zone in northwestern China, was investigated to assess land-use change dynamics by the combined use of satellite remote sensing and geographical information systems (GIS), and to explore the interaction between these changes and the environment. Images were classified into six land-use types: cropland, forestland, grassland, water, urban or built-up land, and barren land. The objectives were to assess and analyze landscape change of land use/cover in Heihe River Basin over 15 years from 1987 to 2002. The results show that (1) grassland and barren land increase greatly by 22.3, and 268.2 km2, respectively, but water area decreased rapidly by 247.2 km2 in the upper reaches of Heihe River Basin; (2) cropland and urban or built-up land increased greatly by 174.9, and 64.6 km2, respectively, but grassland decreased rapidly by 210.3 km2 in the middle reaches of Heihe River Basin; and (3) barren land increased largely by 397.4 km2, but grassland degraded seriously and water area decreased obviously by 313.3, and 21.7 km2, respectively in the lower reaches of Heihe River Basin. These results show that significant changes in land-use occur within the whole basin over the study period and cause severe environmental degradation, such as water environmental changes (including surface water runoff change, decline of groundwater table and degeneration of surface water and groundwater quality), land desertification and salinization, and vegetation degeneracy.  相似文献   

12.
为探讨黄土高原地区的生态恢复,以半干旱黄土丘陵区安家沟小流域的气象、土壤水分、地形图和土地利用图(1982年和2002年)为源信息,分析了不同植被类型的蒸散量和生态用水量、流域生态用水量及其与气候和土地利用变化的关系。研究结果表明:(1)流域土地利用结构从1982-2002年间变化较大,农地(特别是梯田)增加较快,乔木林地急剧减少,主要表现为毁林、开荒和造田;(2)研究区内各种植被/土地利用类型的蒸散量和生态用水都极大地受控于气候(特别是降雨量)的影响,其年际差异较大;(3)不同植被/土地利用类型间的蒸散量和生态用水差异明显,在各个年份乔灌林的生态用水量均大于农作物和自然草地的蒸散量和生态用水量,但生态用水的差异程度小于蒸散量的差异程度;(4)以自然草地(即荒草地)为标准,农作物的蒸散量和自然草地接近,但乔灌林地的蒸散量和生态用水量均远高于自然草地,难于实现土壤水分平衡;(5)流域土地利用结构的变化(主要是强耗水植被的减少)减小了流域生态用水量,增强了流域的水分平衡能力。  相似文献   

13.
Urbanization has been an important component of land use and land cover change. Quantifying land use patterns and their changes is essential for monitoring and assessing the impact of urbanization. Data on existing and changing land use provide crucial clues for future development. Combining the application of remote sensing with geographic information systems (GIS) data, this study accomplishes (i) the creation of time-series land use maps in the core urban area of the city of Hangzhou, China; (ii) the examination of the land use cross-tabulation matrix to assess the transitions between land use types; and (iii) the introduction of a new asymmetric relation analysis method to explore the dependency relationship of different times in land use. The investigation was based on a 12-year time series dataset (1990–2002), compiled from fine-resolution satellite imagery and GIS-based maps. The results of the study showed that, first, there are strong associations between different stages (1990, 1996, and 2002) in land use development, and, secondly, the dependency between land use states was asymmetric in both stages of development. In addition, urbanization in Hangzhou has resulted in notable increases in the surface area of urban land and sharp decreases in the surface area of cropland.  相似文献   

14.
Karst rocky desertification (KRD) is one major type of desertification which is under irrational human impact on the vulnerable eco-geo-environment. In this study, Zhudong fengcong rocky desertification landscape was selected to investigate the land use types distribution law in different rock types and the KRD land in different land use types. KRD data was determined by user–computer interactive interpreting method from Aster images in 2004, according to the exposed ratio of rock, the coverage of vegetation and soil in 0.2 km2 unit, integrating with land utilizing present situation map, hydrogeology map, relief map, vegetation map, soil distribution map, as well as the practical investigation and the population census datum in 2002. Results showed that the occurrence ratio of KRD land is different in land use types and rocky assemblages obviously; land cover has a strong impact upon KRD. The sloping cropland distributed in homogenous limestone has a higher occurrence ratio of light KRD, secondly, is in the limestone interbedded with clastic rock. Light KRD land was dominated by shrubland, and sloping cropland accounts for 11.67% of it, moderate KRD land was dominated by moderate coverage grass slopes, strong and extremely strong KRD was dominated by rocky dry land which is difficult to use.  相似文献   

15.
 Three dolines (sinkholes), each representing different land uses (crop, grass, and forest) in a karst area in East Tennesse, were selected to determine soil erosional and depositional rates. Three methods were used to estimate the rates: fallout radiocesium (137Cs) redistribution, buried surface soil horizons (Ab horizon), and the revised universal soil loss equation (RUSLE). When 137Cs redistribution was examined, the average soil erosion rates were calculated to be 27 t ha–1 yr–1 at the cropland, 3 t ha–1 yr–1 at the grassland, and 2 t ha–1 yr–1 at the forest. By comparison, cropland erosion rate of 2.6 t ha–1 yr–1, a grassland rate of 0.6 t ha–1 yr–1, and a forest rate of 0.2 t ha–1 yr–1 were estimated by RUSLE. The 137Cs method expressed higher rates than RUSLE because RUSLE tends to overestimate low erosion rates and does not account for deposition. The buried surface horizons method resulted in deposition rates that were 8 t ha–1 yr–1 (during 480 yr) at the cropland, 12 t ha–1 yr–1 (during 980 yr) at the grassland, and 4 t ha–1 yr–1 (during 101 yr) at the forest site. By examining 137Cs redistribution, soil deposition rates were found to be 23 t ha–1 yr–1 at the cropland, 20 t ha–1 yr–1 at the grassland, and 16 t ha–1 yr–1 at the forest site. The variability in deposition rates was accounted for by temporal differences;137Cs expressed deposition during the last 38 yr, whereas Ab horizons represented deposition during hundreds of years. In most cases, land use affected both erosion and deposition rates – the highest rates of soil redistribution usually representing the cropland and the lowest, the forest. When this was not true, differences in the rates were attributed to differences in the size, shape, and closure of the dolines. Received: 10 October 1995 · Accepted: 13 October 1995  相似文献   

16.
植被覆盖是水土流失的重要影响因子,在一定的自然生态背景下,土地利用方式亦決定了植被覆盖特征。为深入探讨植被覆盖季节变化的内在机制,本研究选择地处陕北黄土高原的延河流域,对农地、林地和草地共3种主要土地利用方式,分析其植被覆盖季节变化规律,并进一步对土壤类型和地形特征等生态因子的影响加以比较。研究结果表明,不同土地利用方式下,植被覆盖季节变化产生显著的差异,而相同土地利用方式下,土壤类型的影响最为显著,坡向次之。而影响湿润度的地形特征对植被覆盖的季节变化的影响并不明显。基于上述认识,从改善流域植被覆盖的角度出发,不仅需要通过退耕还林、还草来提升植被覆盖水平,也需配合相应的土壤类型及地形地貌条件改造,才能达到生态格局优化。  相似文献   

17.
选择2005与2012年两期遥感影像,基于RS/GIS技术和转移矩阵数学模型,从景观转移方面对保护区景观要素时空变化进行定量分析,探讨了双河自然保护区在7年内土地利用格局及土地转化规律.结果表明,林地、灌木及草地之间转化较为突出,与保护区的环境因素有直接关系.沼泽、水域、居民地及裸土地因其面积基数小,类间转化量较小.旱田较活跃,除居民地外,其余6类景观都有面积转化为旱地.林地和草地相互转化较为活跃,灌木和林地相互转化较为活跃.研究结果可以为保护区的生态治理和可持续发展规划提供科学依据.  相似文献   

18.
Due to deficient water resources in the Loess Plateau, watershed management plays a very important role, not only for ecological and environmental protection but also for the social development of the region. To better understand the hydrological and water resource variations in the typical watershed of the Loess Plateau and the Qinghe River Basin, the influences of land cover and climate change were analysed, and a SWAT model was built to simulate the response of the hydrological situation to land cover changes that have occurred over the past 30 years. The results demonstrated that the main land cover change occurring in the Qinghe River Basin was the conversion of land cover from grassland to woodland and farmland from the late 1980s to 2010. Woodland and farmland took 87.36 and 10.55%, respectively, from the overall area transferred over 20 years and more than 18% of the total watershed area. Hydrological simulation results indicated that land cover played a predominant role in the hydrological variation of the Qinghe River Basin, although the effects of climate change should not be discounted. The significant changes in land cover could be superimposed by policy orientation and economic requirements. Although it is hard to evaluate the land cover changes and the corresponding hydrological responses in a simple language, related analyses have demonstrated an increasing trend of runoff in the dry season, while there is a somewhat decreasing trend during the flood season in the river basin. There results could be significant and provide a positive influence on both future flood control and the conservation of water and soil.  相似文献   

19.
The Chinese Loess Plateau is suffering from severe soil erosion. The eco-environmental changes of the plateau are believed to have an important influence on global eco-environmental sustainability; hence, this problem has attracted considerable attention from scientists around the world. This study has two purposes; application of remote sensing (RS) and geographic information system (GIS) techniques in the dynamic analysis of eco-environmental changes in the semiarid zone; and using the Longdong region of the Chinese Loess Plateau as an example, to make dynamic analysis of the eco-environmental changes of the region during the 1986–2004 period and identify controlling factors. Landsat Thematic Mapper (TM) data at a spatial resolution of 30 m were used for analysis. Two training areas were selected in Jingning and Qingcheng counties for analysis using 10-m resolution SPOT and Landsat TM data. The satellite RS images were obtained from the Institute of Remote Sensing Application (IRSA), Chinese Academy of Sciences (CAS). Each images was rectified by Albers Equal Area Conic projection based on 1:50,000 scale topographic maps after spectrum preparation of the images. To make the precision within 1 or 2 pixels, the accurate coordinative control points of the two systems were identified. Then the interpretation key was established based on the land use/cover survey in the study area. The images were classified into six primary environmental types (farmland, forest, grassland, water, construction area, and desert) and 25 sub-types using a visual image interactive interpretation method to obtain vector and attribute data. The resultant accuracy of the land use/cover classification reached 95%. Finally, the transformation areas and ratios of various eco-environmental types in the region were calculated to obtain the transition matrixes of eco-environmental types in the two training areas, Jingning and Qingcheng. This study demonstrates that satellite RS and GIS techniques are effective tools to monitor and analyze the eco-environmental changes in the semiarid region. Visual image interactive interpretation based on GIS technique provides comprehensive information on the direction, rate, and location of eco-environmental changes. The transition matrix model can be used to precisely analyze the variation and rates of the eco-environmental types and their spatial distribution. Great land use changes have taken place Longdong during the 1986–2004 period. These eco-environmental changes were driven by natural and human factors. Natural factors influencing the Longdong region of the Chinese Loess Plateau mainly include temperature, water condition, terrain, soil, and erosion; while human activities include over-cultivation, overgrazing, and fuelwood cutting. As viewed from the extent and severity of the influences, human activities play a very important role in altering the eco-environment of the semiarid region. The study results indicate a need for future research and observation in the semiarid region.  相似文献   

20.
This study characterized and compared changes in vegetation condition in areas with different gradients during the past three decades across the entire Loess Plateau. For this purpose, changes in vegetation type and vegetation coverage at sites with 0 – 15° and >15° slope gradients were determined by analyzing land use data and Normalized Difference Vegetation Index (NDVI) data, respectively. The software Arc/Info 9.3, land use transformation matrix, linear regression analysis, and Mann–Kendall test were used for the data processing and analysis. Policy influences, human impacts, and climate variability were also taken into account to find the reasons for vegetation condition change. The results indicated that the “Grain-For-Green” project achieved initial success. Areas of farmland and grassland changed most extensively, and far greater areas of farmland were transformed into forest and grassland than vice versa. Moreover, the conversion of farmland to forest and grassland mainly occurred in areas where slopes exceeded 15°, while grassland was mainly changed to farmland in areas with gentle slopes. Vegetation coverage on the Loess Plateau exhibited overall increases after the implementation of “Grain-For-Green” project. Regions with sparse vegetation have declined sharply, mostly in steeply sloped areas. Vegetation coverage has increased significantly in most regions, particularly in the parts traversed by the principal sediment source of the Yellow River, which could help to control the severe soil and water losses. However, regions with sparse vegetation on the Loess Plateau still covered 71.1 % of the total area in 2010. Therefore, it is important to further increase vegetation coverage in the future.  相似文献   

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