| China South is one of the main regions for rice production in China, where in recent 20 years Brown Planthopper (Nilaparvata lugens (Stal)) (BPH) damaged the rice production seriously. Therefore, the timely and accurate prediction of BPH occurrence is important not only to the rice normal development of the planting region, but also to the sustainable development of regional rural economy.The traditional method used for prediction of BPH disaster is only aimed at one county and lack of spatial factors. Geostatistics methods and GIS were used to simulated the northern boundary of BPH overwintering sites, analyze spatial distribution of BPH disaster levels and built its dynamic model in the whole region from 1981 to 1987 in this study. As a result, China South BPH Disaster Early-warning System based on Web-GIS and Active Sever Page, as well as its preliminary application in Zhejiang region, were designed and developed. The web was a internet software system, which integrated GIS, simulation model, expert system and multimedia technology. Besides, effects of rice leaf blast on spectrum reflectance of rice was studied simply.The main contents of this study are as follows:1. Establishment of GIS database for BPH in China SouthArc View 3.2 GIS and FoxPro 6.0 were used to develop database for BPH. The database included spatial and attribute database. The spatial database included China's boundary map, river map, road map, elevation map, soil category map, etc. and the attributes database included BPH disaster levels, meteorologic phenomena. The GIS database provided primary data for BPH spatial analysis.2. Establishment of China digital terrain model (DTM) based on GISUsing the principles and approaches of building DTM based on GIS, China Digital Elevation Model (DEM) was generated with the distance weighted average interpolation of shifting imitation for dispersed elevation points. On the basis of the DEM, mathematical models for DTM were built with numerical value interpolating imitation for dispersed elevation points. The average elevation of ground135unit, relative elevation, elevation difference, elevation variation, slope, aspect, ground roughness, ground formation, gully feature lines and hill ridge, valley density, gully depth, and others were extracted. Moreover, 3D model of China topographic map with shade slope and sunny slope was structured. The result was applied to the simulation of January average temperature in China and the computation of northern boundary of BPH overwintering sites.3. Definement and simulation of northern boundary of BPH overwintering sites based on CIS: As a tool of Geostatistical theory and Kriging interpolation method, the simulation ofineteorologic factors and northern boundary of BPH overwintering sites were discussed with climatic statistics. The results are consistent with historical research on the whole.4. Analysis on BPH disaster spatial distribution and its dynamic models:Statistical theory and GIS method were used to analyze BPH disaster level spatial distribution and its dynamics with inner-years and inter-years in China South from 1981 to 1987. The result of traditional statistics showed that the distribution pattern of BPH disaster level is regular on large scale, and the result of Geostatistics indicated that BPH disaster level was correlated to the spatial factor., but the range changed greatly in 1981-1987. The trend of BPH disaster is serious with the direction from south-west to north-east. The BPH high risk regions located mainly Fujian, zhejiang, Hunan and Guangxi, and lower risk ones lied in Sichuan, Chongqing, yunnan, Guizhou, and others were middle risk. The disaster level, regional distribution, directional trend of BPH were different in inner-years and inter-years. The disaster trend was that the BPH risk increased from 1981 to 1983, decreased greatly in 1984, aggravated in 1985 and 1986, and became serious in 1987. The spatial semivariance models of BPH were built on the basis of these result...
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