نتایج جستجو برای: vegetation

تعداد نتایج: 47633  

Journal: :Remote Sensing 2016
Eva Husson Frauke Ecke Heather Reese

Aquatic vegetation has important ecological and regulatory functions and should be monitored in order to detect ecosystem changes. Field data collection is often costly and time-consuming; remote sensing with unmanned aircraft systems (UASs) provides aerial images with sub-decimetre resolution and offers a potential data source for vegetation mapping. In a manual mapping approach, UAS true-colo...

2003
M. G. Sanderson C. D. Jones W. J. Collins C. E. Johnson R. G. Derwent

[1] The effect of climate change on vegetation, isoprene emissions and surface ozone levels was investigated using a global three-dimensional general circulation model coupled to a dynamic vegetation and chemistry models. Integrations for the 1990s and 2090s were performed. Isoprene emissions increased from 549 Tg yr 1 (1990s) to 736 Tg yr 1 (2090s) as a result of climate change with fixed vege...

2017
Zhiwei Wang Qian Wang Xiaodong Wu Lin Zhao Guangyang Yue Zhuotong Nan Puchang Wang Shuhua Yi Defu Zou Yu Qin Tonghua Wu Jianzong Shi

The Qinghai-Tibetan Plateau (QTP) contains the largest permafrost area in a high-altitude region in the world, and the unique hydrothermal environments of the active layers in this region have an important impact on vegetation growth. Geographical locations present different climatic conditions, and in combination with the permafrost environments, these conditions comprehensively affect the loc...

Journal: :Remote Sensing 2015
Yunbo Bi Hongjie Xie

In arid regions, C3 vegetation is assumed to be more sensitive to precipitation and CO2 fertilization than C4 vegetation. In this study, normalized difference vegetation index (NDVI) is used to examine vegetation growth in the arid Lower Heihe River Basin, northwestern China, for the past three decades. The results indicate that maximum NDVI (MNDVI) of the area increases over the years and is s...

Journal: :desert 2012
h. azarnivand m.a. zare chahouki h. joneidi

one of the characteristics in iranian model of desertification potential assessment (imdpa) is vegetation. sincevegetation is very important factor in the degradation of land, so some indices were determined for this item in order toevaluate desertification potential of arid, semi arid and arid sub humid areas of iran. the indices included vegetationcondition, exploit and revegetation. to calib...

Journal: :Remote Sensing 2016
Felix Ndayisaba Hao Guo Anming Bao Hui Guo Fidele Karamage Alphonse Kayiranga

Knowledge of current vegetation dynamics and an ability to make accurate predictions of ecological changes are essential for minimizing food scarcity in developing countries. Vegetation trends are also closely related to sustainability issues, such as management of conservation areas and wildlife habitats. In this study, AVHRR and MODIS NDVI datasets have been used to assess the spatial tempora...

Journal: :Remote Sensing 2014
Weicheng Wu

A large number of vegetation indices have been developed and widely applied in terrestrial ecosystem research in the recent decades. However, a certain limitation was observed while applying these indices in research in dry areas due to their low sensitivity to low vegetation cover. In this context, the objectives of this study are to develop a new vegetation index, namely, the Generalized Diff...

2017
Wenqian Zhao Xiang Zhao Tao Zhou Donghai Wu Bijian Tang Hong Wei

Along with global climate change, the occurrence of extreme droughts in recent years has had a serious impact on the Amazon region. Current studies on the driving factors of the 2005 and 2010 Amazon droughts has focused on the influence of precipitation, whereas the impacts of temperature and radiation have received less attention. This study aims to explore the climate-driven factors of Amazon...

Journal: :Journal of the American Mosquito Control Association 2004
J A Jiannino W E Walton

The abundance of mosquito larvae and adult production were measured in 3 vegetation treatments and 2 species of emergent macrophytes in replicated wetland mesocosms (12 x 80 m). During the 8-wk study, no significant differences were found in abundances of larvae and emerging adult mosquitoes among the vegetation treatments: 100% of the surface area in emergent vegetation, 50% of the surface are...

2009
S. C. Dekker H. J. de Boer

Terrestrial vegetation influences climate by modifying the radiative-, momentum-, and hydrologicbalance. This paper contributes to the ongoing debate on the question whether positive biogeophysical feedbacks between vegetation and climate may lead to multiple equilibria in vegetation and climate and consequent abrupt regime shifts. Several modelling studies argue that vegetation-climate feedbac...

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