Invasive Characteristics, Spatial Distribution And Sampling Technique Of Dendroctonus Valens Population

Red turpentine beetle(RTB), Dendroctonus valens LeConte was a destructive forest invasive species in China, it mainly attacks Pinus tabulaeformis, P. bungeana and P. armandii. So far it has spread rapidly to the provinces of Shanxi, Hebei, Henan and Beijing since its first outbreak in Shanxi province in 1998, and caused extensive tree mortality. As an invasive alien species, the bionomics and occurrence, response to host volatiles and host preferences of this pine beetle in China are different from what is known of the beetle in its native range in North America. Studying damage characteristics and the law of occurrence of D. valens population, Which can help us to explain the population expansion and colonization mechanism, and to provide a good reference point for adopting suitable control measures.The invasion of different health stages of P. tabulaeformis was analyzed based on niche theory. In addition, historical data on D. valens was examined to establish its invasive characteristics in China; Space-time dynamic of D. valens population was analyzed by using geostatistical methods in the pure P. tabuliformis forest and mixedwood stands which at different damage levels in Lingkongshan Forest Farm; The spatial distribution pattern of D. valens population was investigated by traditional methods, geostatistical methods in Xiaolongmen Forest Farm and Lingkongshan Forest Farm; The spatial sampling technique of D. valens was also studied, and then compared with traditional sampling technique,and have reached the following conclusions:â‘ D. valens originally invaded weak and injured wood, but now it mainly invades both healthy and mild weak wood, and is a primary pest.â‘¡The spatial dynamics showed that the populations increased in lightly and heavily infested stand of pure P. tabuliformis forest, but stable in mixedwood stands in the same year; and the populations decreased in lightly infested stand of pure P. tabuliformis forest, but increased in heavily infested stand of pure P. tabuliformis forest and mixedwood stands in different years.â‘¢The spatial distribution pattern of D. valens population was investigated by traditional methods in Beijing. It was aggregated in Beijing, probably because D. valens has an innate tendency to aggregate, or because of a combination of this and environmental heterogeneity; The spatial distribution pattern of its population was also analyzed by using geostatistical methods in the pure P. tabuliformis forest and mixedwood stands which at different damage levels in Lingkongshan Forest Farm.:the damage level caused by D. valens differed significantly in the two woodlands. Only 4.9% of trees in lightly-infested woodland were infested compared with 23.6% infested individuals in heavily-infested woodland. Analysis of the isotropic variogram indicated that the distance of spatial dependence of D. valens was 49.400m in the lightly-infested levels of pure P. tabuliformis forest, 47.400m in the heavily-infested one and 73.820m in the mixedwood stands, while the intensity of local spatial continuity was 0.824,0.582,0.762 respectively in the above stands. Intense spatial aggregation distribution pattern of D. valens were observed in the lightly-infested level and heavily-infested level of pure P. tabuliformis forest, while random distribution was observed in the mixedwood forest. It concluded that the difference of spatial distribution of D. valens not only existed in different damage levels of pure forest, but also in different stands types.â‘£The spatial sampling technique combines with the biological characteristics of D. valens population. According to the distance of spatial dependence of D. valens in the lightly-infested levels of pure P. tabuliformis forest, the heavily-infested one and the mixedwood stands, the range of sampling were classified as 30m,30 m and 40m. Comparison of repeated sampling, the average accuracy can reach 89.2%,93.6% and 84.2%, which indicated spatial sampling technique can be widely used for high precision.This study hopes helping to explain the population expansion and colonization mechanism of D. valens, and to provide a good reference point for adopting suitable control measures.