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1.
Potential of the Random Forest Model on mapping of different desertification processes was studied in Muttuma watershed of mid-Murrumbidgee river region of New South Wales,Australia.Desertification vulnerability index was developed using climate,terrain,vegetation,soil and land quality indices to identify environmentally sensitive areas for desertification.Random Forest Model(RFM)was used to predict the different desertification processes such as soil erosion,salinization and waterlogging in the watershed and the information needed to train classification algorithms was obtained from satellite imagery interpretation and ground truth data.Climatic factors(evaporation,rainfall,temperature),terrain factors(aspect,slope,slope length,steepness,and wetness index),soil properties(pH,organic carbon,clay and sand content)and vulnerability indices were used as an explanatory variable.Classification accuracy and kappa index were calculated for training and testing datasets.We recorded an overall accuracy rate of 87.7%and 72.1%for training and testing sites,respectively.We found larger discrepancies between overall accuracy rate and kappa index for testing datasets(72.2%and 27.5%,respectively)suggesting that all the classes are not predicted well.The prediction of soil erosion and no desertification process was good and poor for salinization and water-logging process.Overall,the results observed give a new idea of using the knowledge of desertification process in training areas that can be used to predict the desertification processes at unvisited areas. 相似文献
2.
吉林省西部土地沙化动态变化 总被引：1，自引：0，他引：1
The sandy land of the western part of Jilin Province is located in the ecotone of semi-humid and semi-arid area in the temperate zone of China. The sandy desertification has widely spread in the region because of the vulnerable natural conditions and the unreasonable human activity; as a result of this, the precious land resources and the economic development in the area have been seriously impacted. In this paper, the sandy land ecologic environment geographic information system is established based on the multi-spectral, multi-temporal Landsat TM images and field investigation. The comprehensive indexes of sandy desertification extent assessment which include vegetation degradation, wind erosion extent and soil depth are presented to classify the sandy land in western Jilin into three levels--slight, moderate and severe sandy desertification with the support of GIS platform. The results demonstrate that the sandy desertification has been partly controlled in the past twenty years, except some small sites. However, this doesn‘t necessarily mean that there is nothing for more concern. The two main causes of sandy desertification have not been eliminated yet, one is its natural factor, especially the physical and chemical characters of sandy soil and dry climate; another is the immoderate economic activity of human being that has highly accelerated the sandy desertification process. 相似文献
3.
贵州猫跳河流域土地利用变化和土壤侵蚀(英文) 总被引：4，自引：2，他引：2
Due to the extremely poor soil cover, a low soil-forming rate, and inappropriate intensive land use, soil erosion is a serious problem in Guizhou Province, which is located in the centre of the karst areas of Southwest China. In order to bring soil erosion under control and restore environment, the Chinese Government has initiated a serious of ecological rehabilitation projects such as the Grain-for-Green Programme and Natural Forest Protection Program and brought about tremendous influences on land-use change and soil erosion in Guizhou Province. This paper explored the relationship between land use and soil erosion in the Maotiao River watershed, a typical agricultural area with severe soil erosion in central Guizhou Province. In this study, we analyzed the spatio-temporal dynamic change of land-use type in Maotiao River watershed from 1973 to 2007 using Landsat MSS image in 1973, Landsat TM data in 1990 and 2007. Soil erosion change characteristics from 1973 to 2007, and soil loss among different land-use types were examined by integrating the Revised Universal Soil Loss Equation (RUSLE) with a GIS environment. The results indicate that changes in land use within the watershed have significantly affected soil erosion. From 1973 to 1990, dry farmland and rocky desertified land significantly increased. In contrast, shrubby land, other forestland and grassland significantly decreased, which caused accelerated soil erosion in the study area. This trend was reversed from 1990 to 2007 with an increased area of land-use types for ecological use owing to the implementation of environmental protection programs. Soil erosion also significantly varied among land-use types. Erosion was most serious in dry farmland and the lightest in paddy field. Dry farmland with a gradient of 6°-25° was the major contributor to soil erosion, and conservation practices should be taken in these areas. The results of this study provide useful information for decision makers and planners to take sustainable land use management and soil conservation measures in the area. 相似文献
4.
Carbon and nitrogen mineralization in soils along a desertification gradient in the semiarid Horqin Sandy Land, Northern China 总被引：1，自引：0，他引：1
This experiment was conducted in three sites along a desertification gradient in Horqin Sandy Land, Northern China. Soils una-mended and amended with five types of plant residue in a wide range of C:N ratios from 9.9 to 82.2 were incubated for 70 days, during which C and N mineralization were measured. Along the desertification gradient from fixed sand dune to semifixed, and mobile sand dune: cumulative CO2-C produced from the unamended soils was 231.6, 193.3 and 61.9 μg/g, respectively, while net inorganic N was 22.9, 17.6 and 0.9 mg/kg. Soils amended with residues produced more CO2-C than the unamended soils across all sites. During the first 10 days, C mineralization rate of residue-amended soils decreased with the increase of C:N ratio at each site. However, the mineralization rates were poorly correlated with the C:N ratio in subsequent stage of incubation. Soils of mobile sand dune amended with higher C:N ratio (more than 32) residues produced less CO2-C than that of fixed and semifixed sand dune. NO3--N was the predominant form of inorganic N during the mineralization process in sandy soils. Carbon-to-nitrogen ratio (C:N) can be regarded as a predictor of the speed of N mineralization in sandy soil. The more C. microphylla residue with the lowest C:N ratio (9.9) added in soils, the more net inorganic N released. Our results suggest that C. microphylla residue when added to soil would potentially provide short-term plant available N and improve the soil quality in sandy land. The desertification process postponed the release of inorganic N from plant residues. 相似文献
5.
The study developed a feasible method for large-area land cover mapping with combination of geographical data and phenological characteristics, taking Northeast China (NEC) as the study area. First, with the monthly average of precipitation and temperature datasets, the spatial clustering method was used to divide the NEC into four ecoclimate regions. For each ecoclimate region, geographical variables (annual mean precipitation and temperature, elevation, slope and aspect) were combined with phenological variables derived from the moderate resolution imaging spectroradiometer (MODIS) data (enhanced vegetation index (EVI) and land surface water index (LSWI)), which were taken as input variables of land cover classification. Decision Tree (DT) classifiers were then performed to produce land cover maps for each region. Finally, four resultant land cover maps were mosaicked for the entire NEC (NEC_MODIS), and the land use and land cover data of NEC (NEC_LULC) interpreted from Landsat-TM images was used to evaluate the NEC_MODIS and MODIS land cover product (MODIS_IGBP) in terms of areal and spatial agreement. The results showed that the phenological information derived from EVI and LSWI time series well discriminated land cover classes in NEC, and the overall accuracy was significantly improved by 5.29% with addition of geographical variables. Compared with NEC_LULC for seven aggregation classes, the area errors of NEC_MODIS were much smaller and more stable than that of MODIS_IGBP for most of classes, and the wall-to-wall spatial comparisons at pixel level indicated that NEC_MODIS agreed with NEC_LULC for 71.26% of the NEC, whereas only 62.16% for MODIS_IGBP. The good performance of NEC_MODIS demonstrates that the methodology developed in the study has great potential for timely and detailed land cover mapping in temperate and boreal regions. 相似文献
6.
陕北地区退耕还林还草工程土壤保护效应的时空特征 总被引：1，自引：1，他引：0
This paper looks at the Green for Grain Project in northern Shaanxi Province.Based on remote sensing monitoring data,this study analyzes the locations of arable land in northern Shaanxi in the years 2000,2010 and 2013 as well as spatio-temporal changes over that period,and then incorporates data on the distribution of terraced fields to improve the input parameters of a RUSLE model and simulate and generate raster data on soil erosion for northern Shaanxi at different stages with a accuracy verification.Finally,combined with the dataset of farmland change,compared and analyzed the characteristics of soil erosion change in the converted farmland to forest(grassland)and the unconverted farmland in northern Shaanxi,so as to determine the project’s impact on soil erosion over time across the region.The results show that between 2000 and 2010,the soil erosion modulus of repurposed farmland in northern Shaanxi decreased 22.7 t/ha,equivalent to 47.08%of the soil erosion modulus of repurposed farmland in 2000.In the same period,the soil erosion modulus of non-repurposed farmland fell 10.99 t/ha,equivalent to 28.6%of the soil erosion modulus of non-repurposed farmland in 2000.The soil erosion modulus for all types of land in northern Shaanxi decreased by an average of 14.51 t/ha between 2000 and 2010,equivalent to 41.87%of the soil erosion modulus for the entire region in 2000.This suggests that the Green for Grain Project effectively reduced the soil erosion modulus,thus helping to protect the soil.In particular,arable land that was turned into forest and grassland reduced erosion most noticeably and contributed most to soil conservation.Nevertheless,in the period 2010 to 2013,which was a period of consolidation of the Green for Grain Project,the soil erosion modulus and change in volume of soil erosion in northern Shaanxi were significantly lower than in the previous decade. 相似文献
7.
This study presents an analysis of the spatial-temporal distribution of 230 archaeological sites in Guizhou Province, Southwest China for three selected time periods from the Paleolithic Age to the Shang-Zhou Dynasties. The relationship between archaeological sites distribution and environmental changes is also discussed based on paleo-environmental proxies of δ18O and δ13C recorded in stalagmites from Southwest China. The results show that: in the Paleolithic Age(260–10 ka BP), archaeological sites were concentrated in the central, northwestern and southwestern parts of Guizhou, where the high-altitudinal karst landforms with many natural caves suitable for human habitation are developed. In the Neolithic Age(10–3.6 ka BP), most of human settlements were concentrated in the central, northwestern and southwestern parts, while, a fewer sites were found on river terraces in the southern and eastern parts, and the intermontane basins in the central and western Guizhou. During the Shang-Zhou Dynasties(3.6–2.2 ka BP), the sites were mainly distributed in the intermontane basins and on river terraces, which were suitable for primitive aerial farming. The analysis of paleo-environmental proxies of δ18O and δ13C since 260 ka BP suggested that climate fluctuations had little impact on human settlements in this study area. The distinct physical environment, especially the spatial patterns of karst landforms and arable land played an important role in the archaeological sites distribution of Guizhou. 相似文献
8.
地下水位变化对干旱区植被盖度的影响及其空间变异特征 总被引：5，自引：0，他引：5
Sampling and testing are conducted on groundwater depth and vegetation coverage in the 670 km^2 of the Sangong River Basin and semi-variance function analysis is made afterwards on the data obtained by the application of geo-statistics. Results showed that the variance curve of the groundwater depth and vegetation coverage displays an exponential model. Analysis of sampling data in 2003 indicates that the groundwater depth and vegetation coverage change similarly in space in this area. The Sangong River Basin is composed of upper oasis, middle ecotone and lower sand dune. In oasis and ecotone, influenced by irrigation of the adjoining oasis, groundwater level has been raised and soil water content also increased compared with sand dune nearby, vegetation developed well. But in the lower reaches of the Sangong River Basin, because of descending of groundwater level, soil water content decreased and vegetation degenerated. From oasis to abandoned land and desert grassland, vegetation coverage and groundwater level changed greatly with significant difference respectively in spatial variation. Distinct but similar spatial variability exists among the groundwater depth and vegetation coverage in the study area, namely, the vegetation coverage decreasing (increasing) as the groundwater depth increases (decreases). This illustrates the great dependence of vegetation coverage on groundwater depth in arid regions and further implies that among the great number of factors affecting vegetation coverage in arid regions, groundwater depth turns out to be the most determinant one. 相似文献
9.
Plant communities were sampled in the lower reaches of the Tarim River,Xinjiang,The results showed that there are 23 species belonging to 21 genera in 11 families,most of which have low occurrence frequency in quadrats.The most common species is Tamarix ramosissima,which occurred in 17 sites accounting for 89.47% of the total 19 sites,Quantitative classification (TWINSPAN) and ordination(CCA) methods were used to study the distribution Patterns of 23 plant species in 19 sites in this valley.TWINSPAN results showed that the plant communities in the middle reaches of the Tarim River could be divided into 3 groups and the sampling sites could be diveded into 7 types in 3 groups .CCA results were consistent with TWINSPAN results ,and showed species distribution patterns correlated with major environmental variables of groundwater level and soil moisture. 相似文献
10.
Soil erosion by wind is one of the most important processes in the changing the earth’s surface in semi-arid areas,Thus it is of great importance to study soil-erosion action.Using integrated technologies of remote sensing and geochemistry radioactivity iso-tope to extract regional soil-erosion information and to calculate quantity of soil erosion is accomplished successfully in this paper by means of beneficial experiments in the Talatan region of the Gonghe Basin,which is located in northeastern Qinghai-Tibet Pla-teau in China.The results show that the soil erosion by wind is not intensive in this region;the erosion types belong to the classes of very-soft erosion and soft-erosion type,which account for 47.12 percent and 35.58 percent,respectively,of the total study area.In total,two kinds of soil erosion account for 82.70 percent of the study area;only a small area belongs to the classes of severe erosion and very-severe erosion;this area is about 22.14 km2.Severe deposition activity has taken place in this region,and has appeared in a large area(322.67 km2),which accounts for 11.78 percent of the total study area.The results of this study show that soil erosion and deposition inventories are 870,000-1,150,000 tons and 550,000-780,000 tons,respectively,per year.The soil in-ventory shows about 320,000-370,000 tons from Talatan to Longyangxia reservoir per year.Using remote-sensing technology and 137Cs techniques is a valid means to analyze and to evaluate the quantity of soil erosion by wind in semi-arid environments. 相似文献
11.
12.
玛曲草原是著名的高原牧场,也是黄河上游重要的水源涵养地,通过卫星影像分析和实地观测数据,对其风沙地貌进行分类,以期为沙化草地治理提供参考。玛曲沙化草地的风沙地貌可分为4级17类。横向沙丘(新月形沙丘)主要分布在河岸和黄河的一级或二级阶地上,单个的新月形沙丘最大高度可达12 m, 64%的新月形沙丘迎风坡走向与当地起沙风向一致。分布在古河道或古三角洲的流动和半流动纵向沙丘(沙垄)高度小于3 m,51%的沙垄走向与当地起沙风向相同。低山上的沙垄和沙片出现在山顶或其阳坡,地形过渡带形成风蚀坎。风蚀洼地与固定和半固定沙地伴生,60%左右的风蚀洼地横切面为不规则椭圆和马蹄形;其深度与长轴呈正比例函数关系。古(现代)沉积物提供了丰富的沙源,大风、冻融、土层的岩性差异、脆弱的植被、人类过渡干扰和微地形促成了玛曲草地沙化和风沙地貌分异。通过对风沙地貌分类、分析,提出了以保护草皮免受破坏,为防止玛曲草地沙化的主要措施。 相似文献
13.
科尔沁沙地坨甸相间地区土壤水分空间分布特性分析 总被引：3，自引：1，他引：3
固定沙丘、半固定沙丘、流动沙丘、甸子地等不同地貌的相间分布是科尔沁沙地的主要地貌特征之一。在这种特殊的坨甸相间地貌中，土壤水分的空间分布必定有其特殊性。在科尔沁沙地坨甸相间地区的各种地貌类型区进行了土壤层及植被根系层水分状况的实地调查及室内实验。基于实验结果分析出沙地固定沙丘、半固定沙丘、流动沙丘、甸子地不同地貌类型的土壤水分的空间变异特性，并结合四种不同地貌类型区的土壤水分空间分布特征，按照表层、中间层和底层进一步对比分析了不同地貌土壤水分的变化和分布，这对于了解科尔沁沙地土壤水分的变化规律及其与地貌类型的关系，具有一定的意义。 相似文献
14.
科尔沁沙地生态系统典型土壤养分空间分布特征 总被引：15，自引：7，他引：8
通过对位于科尔沁沙地中南部的奈曼旗中部沙地灌溉农田、旱作农田和流动沙丘土壤有机C和全N含量空间分布特征的分析发现:由灌溉农田、旱作农田到流动沙丘,土壤10cm深度内有机C和全N的含量与相对高度的变化密切相关。随着相对高度的增加,上述土壤的有机C和全N的含量逐渐减少,而且全N含量比有机C含量与相对高度的相关性更为显著。从旱作农田到流动沙丘有机C和全N的含量随着相对高度的减小而减少。如果不考虑灌溉农田和流动沙地土壤,旱作农田土壤有机C和全N含量与相对高度的相关性显著程度更高。科尔沁沙地中部沙质灌溉农田土壤全N和有机C含量的垂直分布呈锯齿状,表现为明显的多'峰谷'性,这种变化与土壤的粘土层/有机质层和沙层交错分布的特点有关。尽管研究区的土壤发生了明显的空间变化,但是土壤的全N含量和有机C含量之间依然存在着显著的相关性 相似文献
15.
鄱阳湖沙地是亚热带湿润区典型风沙化土地,土地沙化问题严峻。鄱阳湖沙地研究多在小范围开展,研究意义有限,应在多处进行沙地粒度比对研究。选取庐山市、都昌县、永修县和南昌市新建区等沙地样品57个,分析其粒度特征。结果表明:(1)鄱阳湖沙地主要由中沙、细沙和粗沙组成,三者总含量超90%;Mz均值为1.79Φ,分选较差,呈正偏和尖锐分布;(2)鄱阳湖沙地不同土地类型沉积物表层(0-5 cm)与20-40 cm深度粒度特征存在一定差异,固定沙丘、半固定沙丘、流动沙丘和河滩表层比20-40 cm深度粒径大,但流动沙丘和湿地草滩表层分选优于20-40 cm深度;湿地草滩和河滩优势粒级含量和粒度参数有别于沙丘;(3)鄱阳湖沙地固定沙丘、半固定沙丘和流动沙丘为风成沉积;河滩以河流作用为主,风蚀为辅;湿地草滩是在风力和水动力共同作用下形成的。鄱阳湖沙地沿盛行风向从南到北S、SK、K依次减小,风沙运动多以两跳一悬式为主,以就地起沙为主,河滩湖滩作为补充。 相似文献
16.
本文运用景观生态学原理,借助ArcGIS技术,选择中国北方10个流域及其12个沙漠/沙地,并以西部的和田河和东部的西辽河为典型研究区,在流域与沙区、河道与沙丘两个尺度上,选取景观破碎度指数、景观多样性指数等指标,探讨中国北方干旱、半干旱区沙漠/沙地景观与廊道景观(河流)的空间镶嵌格局特征。结果表明：在流域与沙区尺度上,内流区较外流区沙区景观类型复杂,景观破碎度较小,外流区沙区景观结构较为相似;内流区沙区景观指数自西向东呈现出“景观破碎度递增、景观结构复杂性递减”的规律。在河道与沙丘尺度上,在缓冲带范围内,和田河较西辽河沙丘景观类型复杂,景观破碎度较小;景观指数随河道距离的变化呈现出“景观破碎度随距河道距离的加大而逐渐递减,丰富度指数随距河道距离的加大而呈阶梯状递增”的规律;从沙丘斑块类型景观指数上看,西辽河以固定、半固定的简单型沙丘为主,和田河以流动的综合型沙丘为主。主导的沙丘类型景观距离河道越远,面积比例越小,不同沙丘类型的水平景观破碎度随河道距离递减。 相似文献
17.
科尔沁沙地不同生境土壤氮矿化/硝化作用研究 总被引：6，自引：4，他引：2
利用顶盖埋管原位培育法测定了科尔沁沙地不同生境（丘间低地、固定、半固定、半流动和流动沙丘）土壤氮素矿化/硝化速率的月际动态及净矿化/硝化量。结果表明：①沙地土壤无机氮主要以NO-3-N的形式存在,各类生境土壤NH+4-N平均含量比NO-3-N低58.2%~79.7%;②土壤氮素矿化/硝化速率随植被与土壤条件的恶化呈现递减的趋势,从丘间低地到流动沙丘,净矿化速率分别为61.0、43.4、29.1、5.3 mg·m-2·d-1和2.7 mg·m-2·d-1,净硝化速率分别为61.8、46.2、30.1、6.2 mg·m-2·d-1和3.4 mg·m-2·d-1;③从丘间低地到固定、半固定、半流动和流动沙丘,矿化氮总量分别减少28.8%、52.3%、91.4%和95.5%,硝化总量分别减少25.3%、51.3%、90.0%和94.5%;④不同类型生境土壤净硝化氮占净矿化氮的比例都为100%,表明沙地土壤中植物可利用氮素易于淋溶或氨挥发损失。 相似文献
18.
土壤含水率对风沙流结构及风蚀量的影响 总被引：1，自引：0，他引：1
通过对科尔沁沙地典型生境（流动沙丘、沙质草地和农田）的土壤进行风洞试验,分析了不同含水率下3类土壤的风沙流结构、输沙率及总输沙量的变化趋势。结果表明：（1）不同含水率下,3类土壤的输沙率随高度的增加均呈现减小趋势,且有良好的指数函数关系。（2）随含水率的增加,流动沙丘和沙质草地土壤风沙流沙粒的平均跃移高度增加、0—12 cm的输沙率占总输沙率之比增加,农田土壤则相反。（3）不同风速下,3类土壤输沙量与含水率的关系可用指数函数或三次函数关系来描述。（4）基于不同风速下输沙量随含水率增加的斜率变化程度,可将含水率分为3个区间：平稳下降区间、跃变区间和衰弱区间;流动沙丘、沙质草地和农田土壤的含水率跃变区间分别为0.79%—1.01%、1.14%—1.72%和2.77%—4.44%。（5）随土壤含水率上升,总输沙量大小排序发生变化：0.00—0.76%时流动沙丘>沙质草地>农田,0.76%—1.35%时沙质草地>流动沙丘>农田,1.35%以上时农田>沙质草地>流动沙丘。 相似文献
19.
青海共和盆地土壤风蚀的137Cs法研究(Ⅰ)——137Cs分布特征 总被引：3，自引：1，他引：2
土壤风蚀作为土地沙漠化的首要环节,对其准确测定和评估是十分迫切和必要的。放射性核素137Cs作为人类核试验的产物,以其独特的理化性质而成为研究土壤侵蚀和泥沙沉积一种良好的示踪源。137Cs法在水蚀研究领域已取得了显著的进展,而在风蚀研究中的应用却相对不足,目前尚处于探索阶段。作者选择青海共和盆地作为研究区,探讨137Cs法在土壤风蚀研究中应用的可行性。通过对共和盆地不同类型土壤剖面的137Cs取样分析,基本查清了区域137Cs分布的若干特性,测定出不同类型土地137Cs活度的排序为:林地>干湖盆>高寒草原>旱作农田≈干草原>固定沙丘>荒漠草原>流动沙丘>风蚀地,137Cs总量的排序为:干湖盆>林地>流动沙丘>高寒草原>旱作农田≈干草原>固定沙丘>荒漠草原>风蚀地。并分析了一些典型剖面的137Cs深度分布及其机制,将137Cs深度剖面划分为正常剖面、沉积剖面、侵蚀剖面和人为扰动剖面4种型式。沙丘砂由于遭受反复吹失和沉积,其137Cs含量逐渐减小,趋于微量的均匀化;而高寒草原的137Cs含量在区域上也较为均匀,在深度分布上,接近负指数分布曲线保存了相对完好的137Cs初始沉积剖面,是理想的137Cs背景值样点。 相似文献