基于NDVI的西藏自治区草地退化评价模型   总被引：11，自引：0，他引：11  

李辉霞  刘淑珍 《山地学报》2003,21(Z1):69-71

本文选择草地退化三个主要的表征因子草地盖度、牧草生物量和牧草植株高度来反映草地“量”的退化程度,并运用因子分析的方法算出各个表征因子的权重,加权求和得出草地综合评价指数。最后根据NDVI与草地综合评价指数建立草地退化评价模型,为草地退化的遥感宏观评价提供了一种新方法。  相似文献   

高原草地退化遥感监测对象的地学属性分析--以西藏自治区那曲县为例   总被引：5，自引：0，他引：5  

李辉霞  刘淑珍 《山地学报》2003,21(Z1):72-76

本文通过分析那曲县草地退化遥感监测对象的空间分布特征、波谱响应特征和时相特征三个地学属性,得出以下结论:(1)那曲县的自然景观单元分异程度比较低;(2)退化草地植被在TM5、6波段具有高反射值,LAND-SAT TM信息源中具有对草地植被退化敏感的波段TM7,TM5和TM3;(3)高原植被返青比较晚,生长期短,7、8月份是牧草生长旺季。并根据地学属性分析结论选择7月下旬的LANDSAT TM图像作为草地退化动态监测的主要遥感信息源。  相似文献   

High-resolution images reveal rate and pattern of shrub encroachment over six decades in New Mexico, U.S.A.     

S. C. Goslee  K. M. Havstad  D. P. C. Peters  A. Rango  W. H. Schlesinger 《Journal of Arid Environments》2003,54(4):755-767

Encroachment of the shrub Prosopis glandulosa Torr. (honey mesquite) into semi-arid grasslands is a serious concern in the south-western United States, yet little is known about the long-term dynamics of the invasion process. We used ten high-resolution aerial and satellite images taken from 1936 to 1996 to track the population dynamics and spatial pattern of all P. glandulosa greater than 2 m in diameter on a 75 ha area in southern New Mexico.Shrub cover and patch numbers increased from 1936 to the 1970s, then stabilized at 43% cover and 83 patches ha⁻¹. Individual patches were extremely persistent: 95% of the area occupied by shrub patches in 1936 was still occupied in 1996. Recruitment into the 2 m size class was more variable: 0·6–5·2% year⁻¹ (mean 0·8% year⁻¹). Patch-shape complexity increased from 1936 to 1983 as adjacent shrubs merged, and then declined as those clusters filled in and became rounder. Spatial pattern of shrubs showed a distinct trend over time: strongly clustered in 1936 at lag distances up to 250 m, then random arrangement at all scales, and by 1983 pattern was regular at lag distances greater than 100 m. There was no clear relationship with precipitation.The use of remote sensing imagery allowed us to examine one site over time, and revealed patterns in population dynamics and spatial pattern that would not have been visible otherwise. Comparison of field estimates collected in 2001 with 1996 image data suggest that the canopy cover estimates were accurate, but shrub densities were seriously underestimated in the satellite photographs, which do not show shrubs smaller than 2 m diameter. As long as limitations of the imagery are understood, these methods can be applied over a larger and more heterogeneous area to examine environmental correlates of invasion success.  相似文献   

Spit-platform temperate carbonates: the origin of landward-downlapping beds along a basin margin (Lower Pliocene, Carboneras Basin, SE Spain)   总被引：2，自引：0，他引：2  

J. C. Braga  C. Betzler†  J. M. Martín  J. Aguirre 《Sedimentology》2003,50(3):553-563

ABSTRACT Lower Pliocene temperate carbonates exhibit landward‐downlapping beds at the southern margin of the Carboneras Basin in south‐eastern Spain. This rarely documented stratal geometry resulted from the accumulation of bedded bioclastic carbonate sand and gravel by longshore currents along a spit platform located a few hundred metres from the palaeoshoreline. The top of the spit platform was covered by shoals that extended over a gently dipping ramp inclined to the north. On the landward slope of the spit, sediments washed over from the shoal area were deposited in parallel‐laminated beds with a southward dip of 8–11°. These beds aggraded and retrograded after an increase in accommodation space, probably related to an Early Pliocene eustatic sea‐level rise. As a result, the beds downlap onto the underlying unconformity surface in a shoreward direction. Eventually, the depression between the shoreline and the spit platform was filled, and a gentle ramp became established. These Pliocene exposures in the Carboneras Basin and a similar Upper Miocene example in southern Spain suggest that landward‐downlapping stratal geometries can be expected in nearshore temperate carbonates along basin margins, and demonstrate a similarity in sedimentary dynamics to siliciclastic sands and gravels.  相似文献   

用主成分分析和灰色关联度分析评价草原土壤质量   总被引：30，自引：1，他引：30  

李月芬  汤洁  李艳梅 《世界地质》2004,23(2):169-174,200

在吉林西部草原生态环境调查的基础上，对草原土壤进行了理化性质、营养成分等系统测试，选择其中的有机质、金氮、全磷、全钾、水解性氮、速效磷、速效钾、碱化度、pH值等项目作为评价指标，应用主成分分析法，对吉林西部17种草地进行综合评价，将吉林西部草原土壤分为五个等级，并用灰色关联度分析方法进行了对比。结果表明，两种评价方法得出的结论基本一致。  相似文献   

航空物探综合测量在森林和草原区寻找铜多金属矿的试验研究     

孟庆敏 《物探与化探》2004,28(4):337-340

通过航空物探(电、磁)综合站在已知铜钼多金属矿床上的飞行测量结果，根据从已知到未知的原则，建立航空物探(电、磁)综合测量在草原、森林、沼泽区寻找斑岩型铜多金属矿的找矿模式。根据此试验模式圈定的航空物探异常，在进行地面查证时取得很好的地质效果。  相似文献   

甘南草地类型的生态经济价值与功能及其分类经营   总被引：10，自引：0，他引：10  

郭正刚  高新华  刘兴元  梁天刚 《山地学报》2004,22(6):655-660

根据山区景观所具有的3层次功能和指标体系选取的原则,从美学、社会、生态3个方面,初步构建了4个层次的评价指标体系。在此基础上建立综合评判模型,应用于北京市怀柔区9个乡镇,得到如下结果:景观功能评价综合指数处在"较好"标准的有宝山镇和怀北镇;在"一般"标准的有喇叭沟门乡、雁栖镇、九渡河镇、长哨营乡;处在"较差"标准的有渤海镇、玻璃庙镇、汤河口镇。评价结果基本与实际相符,说明建立的评价指标体系与模型是可行的。  相似文献   

内蒙古干草原春季火险预报模型的研究   总被引：4，自引：0，他引：4       下载免费PDF全文

傅泽强  王玉彬等 《应用气象学报》2001,12(2):202-209

该文利用内蒙古锡盟地区1986~1997年的草原火灾及同期气象资料, 采用数学模拟的建模方法, 研制了该地区重点火险区域 (包括4个旗、市) 的春季草原火险天气预报模型。该预报模型综合考虑了火灾发生当日及前期气象要素对草原火险的影响, 试报检验结果可靠, 可用于当地的火险预报, 为防火部门制定防火决策提供依据和指导, 并可产生较大的社会经济效益。  相似文献   

温带气旋爆发性发展的中期背景及预报     

李晓东  马德贞 《气象》1993,19(5):34-38

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阿拉善荒漠三个草地类牧草中化学元素特点的研究   总被引：2，自引：0，他引：2  

付华  陈善科 《中国沙漠》1994,14(2):37-41

对阿拉善荒漠微温干旱、微温极干和暖温极干三个草地类９科４４种牧草中常量元素（Ｎ、Ｃａ、Ｐ）和微量元素（Ｆｅ、Ｍｎ、Ｚｎ、Ｃｕ、Ｃｏ、Ｍｏ、Ｓｅ）含量的变化特征、丰缺程度和生物吸收序列的研究结果表明，该区不同科牧草中各元素的含量变幅很大，但其吸收各元素多寡的趋势基本一致。  相似文献