The Effect On Oncomelania Suvival In The Snail Control And Schistosomiasis Prevention Forest

Beach is the seasonally flooded river plains of the micro-topography, the main landscape is characterized by winter habitat and summer water. The middle and lower reaches of Yangtze River is about 6.3×105 hm~2, which can be used at a large degree. "Eighth Five" has taken "forest-based" bio-engineering measures to carry out comprehensive management and development on the beach. On the one hand, it makes full use of the beach resources; on the other hand, it applies the composite mode of operation to change the native environment, not only making changes to the patterns of biological community, but also creating a different microclimate in the forest, which creates a new way for preventing and controlling Bilharziasis. The growth and reproduction of Oncomelania are essentially in a natural state on the original beach. In addition to plant food affect their death, the main constraint also comes from climatic factors. The former is a relatively stable factor, its food mainly are algae, mosses, ferns and herbaceous plants, while the latter changes with time and space. Poplar is the major timber trees to prevent beach snails, which are stuied on different forest ages and business models for disease prevention. The relationship between the characteristics of understory herbaceous layer structure, snail mortality and microclimate factors, as well as the law between the glycogen changes and the physico-chemical properties of forest soil have practical significance on the exploration of snail population dynamics and its relationship with beach ecosystems.This study was carried out between May 26 and July 16 through field forestry survey and soil sample collection. According to the data during the growing period of Oncomelania from field measurements and the portable automatic weather observation in 2009, applying variance analysis, stepwise regression analysis, etc. to determine the parameters of hydrothermal environment, establish the relationship model between cumulative mortality of Oncomelania and microclimate factors, compare the characteristic results of different vegetations in herb layer and response difference of Oncomelania to the changes of physico-chemical properties in the soil, and eventually evaluate the effects of environmental snail inhibition at the monitoring spot in Huangzhou Beach through the principal component analysis and cluster analysis methods, to provide important information and scientific basis for monitoring the environment of beach and preventing schistosomiasis. The results showed that:(1) Three-year model has the highest mortality of Oncomelania, next is the 5 year-old pure forest with 4-year history, which are followed by one-year forest mixed with medical plants,3 and 1 year-old pure forest, and the last one is the 8 year-old pure forest with 4-year history and native beach.(2) Reed destruction and forest planting had broken the single dominant species community structure in the bottomlnd, increasing the species of plants, the average community coverage and the evenness index, decreasing average height of vegetation. The importantance of original dominant species of Conyza Canadensis and reed decreased due to the plantation of poplar. With the growth of forest, shade-tolerant herbs increased and photophilous herbs reduced, the grass family herbs increased and herbal herbs reduced, the biotope tended towards biochemical direction. Beach forest, in addition to 8 year-old pure forest, the others have significant increases in the average coverage of herbaceous communities, Shannon-Wiener Index, evenness index and Simpson Index, as well as the species diversity.(3) The dominant climate factors impacting cumulative mortality of Oncomelania were 5～10cm of soil moisture and of 0～5cm of soil temperature. Microclimatic factors interact with each other, directly and indirectly contribute to the mortality of Oncomelania through single advantages, synergy, interaction and antagonism effects.(4) After tests on replacement reed with forest, construction of beach ecosystem, the variance analysis on physical properties of 8 types of soil presented insignificant results, however, chemical properties were significantly different. The total nitrogen content in the soil, soil bulk density and total porosity of soil are three most important factors that affect the mortality of Oncomelania. The former is positive correlation with the mortality of Oncomelania, the latter two are negative correlations. As the total porosity is calculated by bulk density, total N and bulk density are considered as two factors, which reflect the soil suitability of breeding Oncomelania more simply and practically; In addition, only the soil-available potassium content affect the glycogen significantly and negatively correlated. (5) Principal component analysis and cluster analysis were applied to investigate 8 indices of 7 typical snail prevention forests in the Huangzhou Beach of Yangtze River,3 principal components were extracted. Hierarchical cluster analysis was adopted to cluster the 3 principal components by factor scoring. On this basis, the principal component score multiplies with its corresponding eigenvalue to get the environmental snail prevention index. The sample filed was divided into 4 categories after cluster analysis. The average of each class were taken to determine grades of snail prevention, the results showed that 3 year-old complex forest of poplar and camellia had the most significant effect of snail prevention, while 1 year-old pure poplars and 1 year-old complex forest of poplars and wheat presented the lowest effects.