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991.
Peter A. Burrough John P. Wilson Pauline F.M. van Gaans Andrew J. Hansen 《Landscape Ecology》2001,16(6):523-546
Previous attempts to quantify topographic controls on vegetation have often been frustrated by issues concerning the number of variables of interest and the tendency of classification methods to create discrete classes though species have overlapping property sets (niches). Methods of fuzzy k-means classification have been used to address class overlap in ecological and geographical data but previously their usefulness has been limited when data sets are large or include artefacts that may occur through the derivation of topo-climatic attributes from gridded digital elevation models. This paper presents ways to overcome these limitations using GIS, spatial sampling methods, fuzzy k-means classification, and statistical modelling of the derived stream topology. Using data from a ca. 3600 km2 forested site in the Greater Yellowstone Area, we demonstrate the creation of meaningful, spatially coherent topo-climatic classes through a fuzzy k-means classification of topo-climatic data derived from 100 m gridded digital elevation models (DEMs); these classes were successfully extrapolated to adjacent areas covering a total of ca. 10000 km2. Independently derived land cover data and middle infrared corrected Landsat TM derived estimates of Normalised Difference Vegetation Index (M_NDVI) at 575 independently sampled sites were used to evaluate the topo-climatic classes and test their extrapolation to the larger area. Relations between topo-climatic classes and land cover were tested by 2 analysis which demonstrated strong associations between topo-climatic class and 11 of the 15 cover classes. Relations between M_NDVI and topo-climatic classes proved to be stronger than relations between M_NDVI and the independent cover classes. We conclude that the fuzzy k-means procedure yields sensible and stable topo-climatic classes that can be used for the rapid mapping of large areas. The value of these methods for quantifying topographic controls on biodiversity and the strength of their relations with computed NDVI values warrant further investigation. 相似文献
992.
数量化理论I在土地分级中的应用 总被引:3,自引:0,他引:3
阐述了数量化理论Ⅰ应用于农业综合开发示范小区土地分级地基本原理,并运用这一理论对一个村级水平的示范小区的土地资源进行了实际分级。结果表明,应用这一方法在微地域上能客观、迅速地对土地质量作出综合评价。 相似文献
993.
994.
Using eight morphological parameters with six cluster analysis methods, a set of 21 traditional and four improved Philippine upland rice cultivars (cvs) could be separated into five groups: (1) improved semi-dwarf plant type, (2) improved or 'moderately modified' (short) Indica plant type, (3) traditional tall Indica plant type, (4) traditional tall Japonica plant type and (5) traditional short Japonica plant type. The results emphasized the importance of the separation into Indica and Japonica plant types, but the cultivars could be classified more accurately using growth characteristics such as tillering ability, followed by plant height and leaf area parameters. The clusters containing Indica cvs consistently showed a higher tiller number per plant, a higher growth stage (DC classification) and narrower leaves than clusters with Japonica cvs. The parameters culm length, plant height, leaf area, leaf length and width were represented in subgroups with both long and short expression of the respective characteristic. Use of the existing variability of morphological traits within the group of traditional upland rice cvs should be beneficial in recommendation, breeding, selection and development of upland rice cvs for the different rice ecosystems as well as for the upland rice/rice blast pathosystem. 相似文献
995.
A Comparison of Four Methods of Water Quality Assessment 总被引:2,自引:0,他引:2
In this paper, a back propagation network, a Hopfield network, Fuzzy comprehensive index method and classification of gray are compared in application for water quality assessment. The comparison result shows that the BP network is the best one of these four methods. 相似文献
996.
A strategy for finding smallest reduction of information system is studied by using concept of core in rough set theory. A method of discovering classification rule in databases is proposed. 相似文献
997.
Keyboard input techniques are introduced into on line recognition of Chinese character with the study of chinese character five strokes encoding keyboard input method,and a new approach for on line recognition of unconstrained handwritten Chinese character,Five Strokes Encoding Recognition,is proposed.Besides,the set of character roots of Five Strokes have to be altered slightly to meet the on line recognition technique's features. 相似文献
998.
The problems of stroke extraction and character root recognition were studied, and the strategies and the algorithms related to the problems were proposed or developed. Based on observing and studying on the writing styles and the composition features of free handwritten Chinese characters, the strategies and the algorithms, which have been showed by experimental results, have the advantages of high degree of steadiness and tolerance to character variance. 相似文献
999.
For the first time in this paper the forests ofBetula platyphylla in Daxing’an Mountains are subdivided by phytosociological methods. Three community types ofB. platyphylla forest have been differentiated, e.g.,Rhododendron dahuricum-Betula platyphylla community,Corylus heterophylla-Betula platyphylla community andArtemisia stolonifera-Betula platyphylla community. The distributed elevation, stand height, differential species, major composition species of tree layer, shrub
layer and herb layer for each community were detail described
Yang Yongfu, male, born in Sept., 1961; Senior engineer of Central Nursery of Xinlin Forestry Bureau, Daxinganling, P. R.
China
Responsible editor: Chai Ruihai 相似文献
1000.
河北曲周试验区土壤特性与系统分类 总被引:5,自引:0,他引:5
对曲周试验区28个土壤剖面的研究表明,大多数土壤冲积层理较明显,发育程度低,粉砂含量高,盐化现象普遍,人类活动迹象清晰可见,长期灌溉导致明显淋淀粘化层出现,按《中国土壤系统分类(修订方案)》,该区土壤分别属于人工为土、淋溶土和雏形土3个土纲中的相应亚纲、土类及亚类;按《中国土壤分类系统(普查)》,分别属于潮土和盐土2个土类中的相应亚类,比较了6个土壤代表剖面在2种分类体系中的地位。 相似文献