Leaf chlorophyll constraint on model simulated gross primary productivity in agricultural systems     

《International Journal of Applied Earth Observation and Geoinformation》2015

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应用面向对象的决策树模型提取橡胶林信息   总被引：4，自引：0，他引：4  

梁守真  陈劲松  吴炳方  陈工 《遥感学报》2015,19(3):485-494

橡胶林的无序和不合理种植引发了一系列的生态问题,快速监测橡胶林空间分布及动态变化,对橡胶的合理种植、区域生态环境保护以及有关部门的规划决策有重要的指导意义。以MODIS归一化植被指数NDVI时间序列数据和多时相的Landsat TM数据为基础分析橡胶林的季相和光谱特征,确定橡胶识别的关键时期和特征参数,构建面向对象的决策树分类模型,开展橡胶信息提取研究。结果表明,多时相的遥感数据可反映橡胶的季相特征,以TM数据为基础计算得到的陆表水分指数LSWI和归一化植被指数NDVI可作为橡胶识别的光谱特征参数,橡胶休眠期是利用遥感方法进行橡胶提取的最佳时期。相比于单时相数据,利用包含橡胶关键物候期的多时相遥感数据能得到更高的橡胶林提取精度。  相似文献   

Multi-temporal remote sensing data applied in automatic land cover update using iterative training sample selection and Markov Random Field model     

Kun Jia  Xiangqin Wei  Lei Zhang  Xin Du  Yunjun Yao 《国际地球制图》2015,30(8):882-893

Automatic land cover update was an effective means to obtain objective and timely land cover maps without human disturbance. This study investigated the efficacy of multi-temporal remote sensing data and advanced non-parametric classifier on improving the classification accuracy of the automatic land cover update approach integrating iterative training sample selection and Markov Random Fields model when the historical remote sensing data were unavailable. The results indicated that two-temporal remote sensing data acquired in one crop growth season could significantly improve the classification accuracy of the automatic land cover update approach by approximately 3–4%. However, the support vector machine (SVM) classifier was not suitable to be integrated in the automatic land cover update approach, because the huge initially selected training samples made the training of the SVM classifier unrealizable.  相似文献   

Transport and dispersion of particulate Hg associated with a river plume in coastal Northern Adriatic environments     

Covelli S  Piani R  Acquavita A  Predonzani S  Faganeli J 《Marine pollution bulletin》2007,55(10-12):436-450

The role of suspended particulate matter (SPM) as an important carrier of mercury (Hg) dispersed into the Gulf of Trieste and in the adjacent Grado lagoon (Northern Adriatic Sea) was studied during a high Isonzo River inflow and the resulting river plume formation. Despite the fact that extreme flood events are rare during the year, they account for most of the PHg influx (37-112 ngL(-1)) into the Gulf of Trieste. When the river plume is diverted to the SW under the influence of an E-NE wind, the tidal flux acts as a "transport belt" carrying the PHg, mostly inorganic, into the Grado lagoon. A preliminary estimation indicates that the amount of PHg entrapped in the lagoon basin following a tidal semi-cycle accounts for 1.4 kg/12h, which corresponds to about 49% of the total Hg carried by the tidal flow. These findings should be considered in future remediation strategies in the lagoon environment.  相似文献   

Recolonization and recovery dynamics of the macrozoobenthos after sand extraction in relict sand bottoms of the Northern Adriatic Sea     

Simonini R  Ansaloni I  Bonini P  Grandi V  Graziosi F  Iotti M  Massamba-N'siala G  Mauri M  Montanari G  Preti M  De Nigris N  Prevedelli D 《Marine environmental research》2007,64(5):574-589

The long-term effects of sand extraction on macrozoobenthic communities were investigated in an offshore area in the Northern Adriatic Sea characterised by relict sands formed during the last Adriatic post-glacial transgression. Surveys were carried out before, during and 1, 6, 12, 18, 24 and 30 months after extraction at three impacted and seven reference stations. The operations did not influence the physical characteristics of the sediment, but they caused almost complete defaunation at dredged sites. Univariate and multivariate analyses highlighted that the macrozoobenthic community responses to the dredging operations were (1) a rapid initial recolonisation phase by the dominant taxa present before dredging, which took place 6-12 months after sand extraction; (2) a slower recovery phase, that ended 30 months after the operations, when the composition and structure of the communities were similar in the dredged and reference areas. This pattern of recolonisation-recovery fits well with the commonly encountered scenario where the substratum merely remains unchanged after marine aggregate extraction.  相似文献   

人为扰动对陆面水分能量的影响——以沩水河流域为例     

刘双  谢正辉  曾毓金  刘斌  高骏强  李锐超 《气候与环境研究》2018,23(6):683-701

以沩水河流域为例,基于陆面模式CLM4.5,建立了综合考虑作物种植、地下水开采及灌溉等人类活动的流域陆面水文模型。利用所发展模型,针对1981~2012年,取500 m空间分辨率,探讨人为扰动对陆面过程的影响。研究表明:1）地下水侧向流使得中下游地区地下水位有所提高,平原地下水埋深分布在4 m左右,山区埋深可达到几十米;模拟的叶面积指数较静态MODIS叶面积指数偏大1左右,由此使得种植区月蒸腾量提高约10 mm,土壤蒸发和地表产流有所减少;在灌溉作用下,作物叶面积指数略增长,蒸散发稍有提高,而在假设水稻采用漫灌的情况下,水库灌溉补偿了作物生长产生的水消耗,提高了该区域土壤湿度,增加潜热通量;研究区地下水开采存在但其水文效应并不显著。2）土地覆盖变化自1990年有较大变动,1990~2000年以林地为主,2000年后以耕地为主,其中,1990~2000年土地覆盖类型变化不明显,2001~2012年耕地面积呈先减少再增加又减少的趋势,林地面积则先增加再减少又增加,耕地与林地在2012年所占比例基本持平;同一土地类型内,植被类型变化较为明显,导致陆面水文模拟结果差异较大。  相似文献   

基于ArcGIS Engine的土地信息管理系统的设计与实现     

陈超  仇阿根  朱芳菲  李玉祥 《全球定位系统》2012,37(2):77-80

在对与土地信息系统建设有关的若干关键技术做出了较为详尽分析的基础上,采用集成开发模式,基于Visual studio2005平台和ArcGIS Engine 9.3,利用C#语言编程实现了该系统。该系统能使土地资源的利用更加合理、管理更加高效与规范。  相似文献   

A geospatial approach to assessing land change in the built-up landscape of Wa Municipality of Ghana     

《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2012,112(2):121-135

ABSTRACT

Urban landscapes are changing in response to changes in socio-economic conditions. Land change scientists seek to understand these land dynamics in the coupled human-environment system of urban landscapes. This study assessed land change in the built-up area of Wa Municipality between 1986 and 2016 using Landsat images. We used the Support Vector Machine algorithm for classifying the images. We recorded image classification accuracies of 97%, 95%, 92% and 96% for the 1986, 1996, 2006 and 2016 classified images, respectively. Our study finds that over the 1986–2016 period, agricultural land and bare land transitioned to build-up land by 9.23% and 3.79%, respectively, as compared to 2.79% for vegetation and 0.05% for water. Our in-municipal level analysis thus shows that urban landscapes could expand more sustainably by targeting other dominant land categories instead of the vegetation cover. The findings in this paper could serve as a spatial model for planning and reducing the unintended socio-ecological impacts of expansion in the built-up area.  相似文献   

The Valley of Chin lee     

《The Journal of geography》2012,111(1):22-23

Abstract

This paper is concerned with an instructional design for the teaching of landform geography. A sequence of organizational problems is examined and suggestions made from a previous study of the southern peninsula of Michigan. Considerations of grid design, selection of terrain parameters, and the problem of regional definitions are assessed from both the historic point of view and the results of the pilot study. Of three basic landform parameters, i.e., average elevations, local relief, and average slope, the single criterion of elevation is advocated for the detection of regional homogeniety over large topographic surfaces. However, the use of local relief as a measure of surface texture is proposed for the delineation of individual terrain compartments. Suggested for all age levels above the elementary school, this project is a feasible design for an oft-neglected aspect of physical geography.  相似文献   

The atmospheric general circulation: Some unresolved issues     

Peter H. Stone   《Dynamics of Atmospheres and Oceans》2008,44(3-4):244-250

Several questions concerning the general circulation for which satisfactory answers are not yet available are discussed. The focus is on the zonal mean heat balance, since problems in our understanding of this balance are a fundamental limitation on our ability to model climate and climate change. The questions are: How strong is the atmosphere's poleward heat transport? What are the relative roles of large-scale eddies and small-scale convection in stabilizing the mid-latitude atmosphere? What are the dynamical mechanisms that maintain the time mean zonal mean state in mid-latitudes? Some suggestions for addressing these questions are given.  相似文献