Community Structure And Function Of Boring Insects In Pine Forest Infected By Bursaphelenchus Xylophilus In Zhejiang Province

In this paper, invasive species Bursaphelenchu xylophilus and its vectors, especially Monchamus alternatus, were token as major objects, the author chose typical forests infected by B.xylophilus and had regenerated after ruined as study areas, guided theoretically by population, community and system ecology, to study community structure and function of insects, mostly boring insects, which would reveal resistance mechanism of pine forest ecosystem. Results as following:1. Monchamus alternatus was the only vector of the pinewood nematode (PWN) at sample pine forests in Zhoushan city and Fuyang city in Zhejiang province. The only way by which B.xylophilus was transported to new pine hosts was the feeding wound gnawed by M. alternatus but not ovipositing wound. M. alternatus developmentis accomplished through frequently nutritional supplement on brunches or twigs, which could be increase the chance of PWN dispersal. And in the forest, it was impossible that the nematodes were transported by mating of pine longhorn beetles.2. We found PWN in lateral root of dying hosts, which showed B.xylophilus could be transported between roots. Through test the opportunity, we believed that PWN had no chances to transmit from dying hosts to healthy ones by adjacency of roots. In addition, rain almost could not as the medium to spread the disease in the forest.3. Competition among boring insects restrained the population increasing of M. alternatus, which decreased the extending of pine wilt disease. In winter, Shirahoshizo patruelis contested resource in dying host trunks with M. alternatus, and Tomicus piniperda inhabited in the crown with the pine longhorn beetle. These two competitors restricted the increasing of M. alternatus population together. However in summer, T. piniperda, S. patruelis and T. minor in e trunks had less competition, because of M. alternatus in adult period. At that time, they mostly accelerate the death of host.4. Tetrigus lewisi is a predatory enemy firstly found in China inhabited in dying Pinus massoniana with M. alternatus. The two insects have the equivalent niches and high niche proportional similarity and overlap. Therefore, predator could control the pine longhorn beetles effectively. We studied biological characters of the click beetle and its activity of controlling M. alternatus potentially. Results showed that in laboratory, the life history of predator was so long and likely beyond a year. Because of slowly-growing, rapidly-preying, and low feed efficiency, they need plentiful food to finish their life cycle. By further study about predatory fuction of the predator to the prey, we consider the Holling II(1959) equation could model the quantity reation between one elater and the longhorn beetles in different density. Acording to the model,the max predatoriness of T. lewisi to M. altematus was 16.9.5. We believed that pines infected by B.xylophilus included 6 stages: healthy, dying, dead, down, and strike(whole), strike(rotted), and took them as habitats of boring insects to study community structure of insects. According to results of the dominances of insects function groups, we concluded that the boring and disintegrated insects played important roles in succession of pine forest. Boring insects accelerated the death of pines, which then were disintegrated by disintegrated insects. The nutrition of trees was absorbed by soil. So, "new niche" was provided for other species.6. By studying community structure of boring insects in predominant arbors in different-type forests, we got a result that fluctuation of the boring insect richness, diversity and abundance had the opposite tendency with the richness of arbors in the forest and the same tendency with the dominance of P. massoniana. M. alternatus damaged more seriously in pure P. massoniana forests than in mixture forests. According to the status that in mixture forests with much broadleaf trees, we considered that mixture forests could resist the pine longhorn beetles. And the damage in P. massoniana forests brought by M. alternatus in middle age forests was more seriously than young ones, weak forests than strong ones.