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1.
选择位于红壤丘陵区的鄱阳湖流域作为研究对象,利用1 km×1 km分辨率的时序SPOT4 VEGETATION数据,对流域内典型土地覆被--常绿覆被的绿度值、峰值、谷值、年均NDVI(NDVI-I)和NDVI年内极差(NDVI MM)等特征值进行了提取。在此基础上,探讨了不同常绿覆被类型的NDVI指数年内季节变化规律。结果表明:时序NDVI指数基本上能够较好地刻画不同常绿覆被类型之间的差异性,植被指数NDVI特征值随覆被的类型及其生长状态有规律地变化,即NDVI年均值和最小值基本上按“常绿阔叶林>常绿针阔叶混交林>常绿针叶林>常绿针叶-落叶混交林”的顺序变化;典型常绿阔叶林的NDVI指数年内变化曲线基本上没有大的起伏波动;常绿针叶林以及常绿针阔叶混交林占主导地位的常绿混交林NDVI指数年内变化比较和缓,但常在8月和11月有所波动;以常绿针叶林为主、但有较多落〖JP2〗叶林混杂其中的常绿混交林,其NDVI指数年内变化曲线基本上呈和缓的单峰型波动。 相似文献
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The use of Normalized difference vegetation index (NDVI) data acquired with multiple satellite sensors has become a necessity in research fields such as agriculture, Land-Use and Land-Cover Change (LUCC) and changes in the natural environment. In this paper, vegetation 10-day composite (VGT-S10) NDVI data with a 1 km×1 km resolution, covering the period from April 1982 to December 2011 and Advanced Very High Resolution Radiometer (AVHRR) Global Inventory Modelling and Mapping Studies (GIMMS) NDVI data with a 8 km×8 km resolution, covering the period from April 1998 to December 2006 were used. The VGT NDVI covering the period from 2007 to 2011 was converted to the GIMMS NDVI for the same period. The vegetation trend during 1982 to 2011 was calculated using the extended NDVI data set.
Climate change has a large impact on the vegetation dynamics. A series of statistical analyses were employed to demonstrate the relationship between NDVI and meteorological data during 1982 to 2005. A multiple correlation analysis was applied to validate the association between the two climatic factors and monthly maximum NDVI (MNDVI). The partial correlation coefficient of MNDVI and each climate factor were calculated respectively to describe the singular influence of each meteorological variable. The results indicated that temperature made a significant positive influence on vegetation growth in the whole Loess Plateau. Precipitation is the most important climatic factor that closely correlates with MNDVI, particularly in arid and semi-arid environments. However, in some wet regions, precipitation is not a limiting factor on vegetation growth. 相似文献
5.
The destruction of land and forced migration during the Anfal attacks against the Kurds in Iraq in the late 1980s has been reported to have severe consequences for agricultural development. A reconstruction program to aid people in returning to their lands was launched in 1991. To assess the agricultural situation in the Duhok governorate during the pre-Anfal (A), post-Anfal (B), reconstruction (C), and present (D) periods, we mapped winter crops by focusing on inter-annual variability in vegetation greenness, using satellite images. The results indicate a decrease in cultivated area between period A and B, and a small increase between period B and C. This supports reports of a decline in cultivated area related to the Anfal campaign, and indicates increased activity during the reconstruction program. Period D showed a potential recovery with a cropland area similar to period A. 相似文献
6.
大规模的农业扩张和全球气候变化导致东北地区发生剧烈的土地利用/土地覆盖变化。本研究分析了研究区1976—2008年的土地利用变化和生长季各月气温的变化趋势,并结合农业扩张程度,探究LUCC对农业扩张和气候变化的响应,为指导农业发展规划和保障国家粮食安全提供理论依据。结果表明,1976—2008年农田面积逐步增加,生长季气温一直呈上升趋势。1976—2001年生长季气温的上升趋势不稳定,气温变化程度较大;2001—2008年,农业扩张放缓,生长季气温上升趋势显著,且上升趋势一直增加,气温变化比上一时期更稳定;且这两个时期农业扩张和气候变化对土地利用强度的影响在南北和东西方向上均存在明显差异。 相似文献
7.
Use of Descriptors of Ecosystem Functioning for Monitoring a National Park Network: A Remote Sensing Approach 总被引:1,自引:0,他引:1
Baseline assessments and monitoring of protected areas are essential for making management decisions, evaluating the effectiveness
of management practices, and tracking the effects of global changes. For these purposes, the analysis of functional attributes
of ecosystems (i.e., different aspects of the exchange of matter and energy) has advantages over the traditional use of structural
attributes, like a quicker response to disturbances and the fact that they are easily monitored through remote sensing. In
this study, we described the spatiotemporal patterns of different aspects of the ecosystem functioning of the Spanish national
parks and their response to environmental changes between 1982 and 2006. To do so, we used the NOAA/AVHRR-GIMMS dataset of
the Normalized Difference Vegetation Index (NDVI), a linear estimator of the fraction of photosynthetic active radiation intercepted
by vegetation, which is the main control of carbon gains. Nearly all parks have significantly changed during the last 25 years:
The radiation interception has increased, the contrast between the growing and nongrowing seasons has diminished, and the
dates of maximum and minimum interception have advanced. Some parks concentrated more changes than others and the degree of
change varied depending on their different environmental conditions, management, and conservation histories. Our approach
identified reference conditions and temporal changes for different aspects of ecosystem functioning, which can be used for
management purposes of protected areas in response to global changes. 相似文献
8.
Yukiyo Yamamoto Thomas Oberthür Rod Lefroy 《Environment, Development and Sustainability》2009,11(3):639-654
In the mountainous regions of northern Laos, shifting cultivation, or slash-and-burn agriculture, is widely practiced. However,
the crop–fallow rotation cycle is becoming shorter owing to forest conservation policies and population pressure, causing
loss of productivity that deleteriously affects farmers’ livelihoods in the region. To investigate regional land use conditions,
we have developed a method of identifying the crop–fallow rotation cycle from Landsat Thematic Mapper (TM) and Enhanced Thematic
Mapper+ (ETM+) data. We assessed the impact of the identified cycle on plant production measured by Normalized Difference
Vegetation Index (NDVI). The study site was an area in Luang Prabang Province. Using eight TM and ETM+ images acquired annually
from 1995 to 2003, except for 1998, when cloud-free data were not collected, we classified land use in each year as crop or
fallow by the presence of vegetation in the late dry season. Conformity with fallow age determined by field investigation
was 69.1%. The cultivation frequency from 1995 to 2002 showed that 77,000 ha (17.3% of the study site) had not been used for
cropping during the period, but 41,000 ha (9.2%) had been used every year. Of the study site, 129,000 ha (29.1%) was cultivated
one or two times, 83,000 ha (18.7%) was three or four times, and 54,000 ha (12.2%) was five or six times. The NDVI of crops
in November did not provide sufficient evidence to prove the assumption that a longer fallow period would result in better
crop yields. Instead, the regeneration of fallow vegetation was evidenced by the higher NDVI values after longer fallow. More
than 8 years would be needed to reach the same NDVI as forest. From the produced maps indicating fallow age and cultivation
frequency, we found that areas with high potential for regeneration decreased as cultivation frequency increased. Areas near
rivers were intensively used, and fallow length was accordingly short. Low-potential areas were found in the western basin
of the Mekong River. This spatial information can be used to detect areas where biomass productivity is at high risk of deteriorating.
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献
9.
2001~2007年天山南坡中段不同植被类型NDVI变化分析——以新疆和静县为例 总被引:4,自引:0,他引:4
利用MODIS数据建立近7年和静县NDVI时间序列,通过采用均值法、最大合成法和一元线性回归法,分析了该区不同植被类型年内变化、年际变化趋势.结果表明,和静县植被季相变化明显,不同植被类型变化幅度差异显著;近7年大部分地区植被存在退化趋势,局部区域植被有所改善;不同植被类型退化程度从大到小为荒漠草原>荒漠植被>草原>高山垫状植被>高寒草原>草甸 沼泽>落叶阔叶林>耕地;平原区植被NDVI的变化主要受人为活动的影响.山区植被NDVI除受季节性放牧影响外,更多的受气候变化的影响. 相似文献
10.
植被是陆地表面主要的覆盖物,也是许多地球系统过程的重要变量。人类活动对植被的影响在区域尺度上是显著的。以重庆市为例,使用滑动平均和SG滤波对SPOT/VGT NDVI时间序列数据进行了平滑处理,结合GDP和人口栅格化数据,从时间序列和空间相关场两个方面分析了植被与人类活动因子之间的时空相关性。结果表明,从1998到2005年,植被的分布和生长状况并没有随GDP和人口的持续增加而增加。在时间序列上,植被覆盖与GDP和人口之间总体上呈显著的负相关关系;在空间上,这种相关关系表现出了较强的异质性。空间相关场表明:较强的负相关主要发生在相对发达的主城区周围,反映了快速的经济发展和城市化使得植被面积和生产力降低;然而在偏远的山区,由于经济落后同时植被覆盖较少,出现了正相关。 相似文献