共查询到10条相似文献，搜索用时 49 毫秒
1.
着重讨论绿量快速测算方法中的原始数据自动采集问题。这里以原LVV基本测算模型的分树种径-高方程（D-HEqs）为基础,通过加权归纳和系统误差调整,给出了测算精度较好的模糊径-高相关方程（G_D_HEq）,LVV测算误差与原基本模型相比仅低7．6％;通过树冠信息提取、噪声去除和边界跟踪等技术,给出了树冠边界周长面积比与冠径的相关方程（P／A_DEq）,并由实验证明了树冠的周长面积比（P／A）对冠径变化敏感。冠径自动提取和计算误差约为10％。该研究不仅改变了原来LVV遥感测算模式中多数原始数据必须通过人工判读量算的现状,也实现了LVV数据更新的自动化。 相似文献
2.
Phenological patterns of wetland vegetation were studied on the Savannah River Site, Aiken, South Carolina, USA, to aid in delineation of wetland vegetation community types and plant species from aerial imagery. Relative phenology patterns were recorded for 16 dominant wetland plant species from May 1984 to June 1985 on the floodplains of three streams. These patterns were identified and compared with aerial photographs acquired in the same season as ground observations. Leafout and leaf senescence varied between and within floodplains. In spite of this variability, vegetation classes and individual species may be distinguished best during the late April leafout period. 相似文献
3.
M. G. HOLMES 《Botanical journal of the Linnean Society. Linnean Society of London》1992,108(2):93-109
HOLMES, M. G., 1992. Monitoring vegetation in the future: radar. The use of radar for remote sensing of the biosphere has several advantages over conventional methods using the visible and infra-red wavebands. These advantages include independence from solar energy, an all-weather capability, and the ability to select an appropriate wavelength to study either the surface layers of vegetation or to penetrate deeper into the canopy to study the properties of undergrowth or the soil substrate. Despite these advantages, radar remote sensing is still in the developmental stage. The mode of operation of the radar instrument, and the physical laws governing the propagation of microwaves in scattering media, introduce some unique aspects for remote sensing of the biosphere.
Increased interest in radar has arisen primarily from the need to make multi-temporal studies of vegetation in areas which are susceptible to cloud cover, such as temperate and equatorial regions. Radar penetrates all but the densest cloud, and therefore overcomes this problem. At the same time, however, many of these wavelengths also penetrate deeply into the crop. As a result, analysis of the principles controlling the interaction of radar wavelengths with vegetation and soil are complex. These principles are discussed in terms of current microwave backscatter models.
Vegetation and soil factors influencing radar backscatter are discussed, and the significance of instrument characteristics such as frequency, polarization and incidence angle are considered. The advantages and disadvantages of radar are reviewed, and particular reference is made to the potential of combining optical and radar studies. 相似文献
Increased interest in radar has arisen primarily from the need to make multi-temporal studies of vegetation in areas which are susceptible to cloud cover, such as temperate and equatorial regions. Radar penetrates all but the densest cloud, and therefore overcomes this problem. At the same time, however, many of these wavelengths also penetrate deeply into the crop. As a result, analysis of the principles controlling the interaction of radar wavelengths with vegetation and soil are complex. These principles are discussed in terms of current microwave backscatter models.
Vegetation and soil factors influencing radar backscatter are discussed, and the significance of instrument characteristics such as frequency, polarization and incidence angle are considered. The advantages and disadvantages of radar are reviewed, and particular reference is made to the potential of combining optical and radar studies. 相似文献
4.
5.
作为草地资源大国,我国正面临严峻的草场退化形势。掌握草场植被盖度的历史演变趋势,是草场退化驱动力识别及风险评估的基础。目前已有研究多以参数回归方法估算植被盖度,但并未充分考虑其苛刻的使用条件。利用Landsat系列卫星遥感影像及地面植被盖度监测资料建立非参数回归——随机森林回归模型,并与传统线性回归方法进行比较,在此基础上应用随机森林回归模型估算近10年来布尔津县草场植被盖度的变化趋势,并对结果的不确定性进行分析。结果显示:传统的线性回归方法很难满足其基本的统计学假设条件,而随机森林模型不但无需进行假设条件检验,而且预测的准确性也优于以往普遍应用的线性模型。基于Landsat ETM+标准数据得到的反演结果较之TM和OLI数据普遍偏小,地表反射率数据虽然可以大幅降低传感器不同对反演结果所造成的影响,但结果仍存在约±10%的不确定性。涉及的草场类型众多,为了提高反演精度,后续研究需要分别计算其植被指数,并尽量减低传感器差异带来的不确定性。 相似文献
6.
Cities are natural laboratories for studying vegetation responses to global environmental changes because of their climate, atmospheric, and biogeochemical conditions. However, few holistic studies have been conducted on the impact of urbanization on vegetation growth. We decomposed the overall impacts of urbanization on vegetation growth into direct (replacement of original land surfaces by impervious built‐up) and indirect (urban environments) components, using a conceptual framework and remotely sensed data for 377 metropolitan statistical areas (MSAs) in the conterminous United States (CONUS) in 2001, 2006, and 2011. Results showed that urban pixels are often greener than expected given the amount of paved surface they contain. The vegetation growth enhancement due to indirect effects occurred in 88.4%, 90.8%, and 92.9% of urban bins in 2001, 2006, and 2011, respectively. By defining offset value as the ratio of the absolute indirect and direct impact, we obtained that growth enhancement due to indirect effects compensated for about 29.2%, 29.5%, and 31.0% of the reduced productivity due to loss of vegetated surface area on average in 2001, 2006, and 2011, respectively. Vegetation growth responses to urbanization showed little temporal variation but large regional differences with higher offset value in the western CONUS than in the eastern CONUS. Our study highlights the prevalence of vegetation growth enhancement in urban environments and the necessity of differentiating various impacts of urbanization on vegetation growth, and calls for tailored field experiments to understand the relative contributions of various driving forces to vegetation growth and predict vegetation responses to future global change using cities as harbingers. 相似文献
7.
城镇绿地是增加城市碳汇的积极因素之一。但城镇绿地植被结构和分布的极高空间异质性、影响植物生产力的环境压力因子的极高空间异质性等,使城镇绿地碳汇水平估算存在很大的不确定性。为此,提出了完全由遥感数据驱动的城镇绿地植被固碳量测算模型。它以分树种单株测算来适应城镇绿地植被结构和分布等的高异质性;以小尺度提取影响植物生产力的主要环境压力和管养模式因子,来适应这些因子空间分布的高异质性。该模型可以用于自动测算城镇绿地植被地上干生物量和地上净第一生产力,它的提出对于评价城镇绿地植被的碳捕获能力和储量分布、碳汇水平、以及由此产生的对城镇地区碳循环和生态承载力等的定量影响具有重要意义。为了论证该技术框架中一些关键技术的可行性,进行了局部试验,并取得了一些进展。 相似文献
8.
Summary Vegetation changes over time are important indicators of condition, and are particularly important as targets or triggers for management. Satellite image data have unique capacities to provide information on changes in vegetation. In particular, Landsat imagery has the spatial resolution and a historical archive that make it relevant to providing information for understanding and management of native vegetation at a range of scales from small remnant to region. Regional and national vegetation monitoring programs based on time series Landsat imagery are now operational in Australia. These programs and their data have huge potential to provide information for conservation and natural resource management questions. They have already found multiple applications, including applications to biodiversity assessment and planning. This paper presents some examples of the delivery and application of satellite image monitoring information in the context of vegetation management. 相似文献
9.
喀斯特土壤主要由白云岩和石灰岩风化而来,植被生长及其分布究竟怎样响应这一特殊地质背景?以人为干扰影响较小的喀斯特自然保护区为研究对象,采用监督分类法对1990年和2011年两期TM影像进行植被分类,并利用景观格局分析方法研究两种岩性上植被变化差异。结果表明,1990年和2011年研究区内两种母岩上均以乔木林和乔灌为主,草灌和草丛分布少,白云岩上乔木林的面积比例大于石灰岩上的比例,而草灌和草丛小于石灰岩上的比例;近20年来白云岩与石灰岩上草丛、草灌、灌丛和乔灌均以正向演替为主,但白云岩上正向演替比例大于石灰岩上的比例;两种岩性上植被斑块连接性均增强、破碎程度均降低,白云岩上植被斑块的破碎化程度和多样性指数较石灰岩上低,内部连接性强。由此可见,喀斯特白云岩较石灰岩有利于草丛、草灌的自然恢复,岩性引起的水土资源配置和养分地球化学循环过程差异制约着喀斯特地区植被的时空格局。 相似文献
10.
冶炼厂粉尘中重金属在环境中迁移及其对策 总被引：2，自引：0，他引：2
以炼铜为主的安徽省铜陵有色公司冶炼厂在生产中,有较多的二氧化硫和重金属粉尘通过108m高的烟囱排入大气。经分析,粉尘中铜、砷、铅的含量很高(铜9.26%,砷2.12%,铅4.46%), 相似文献