| Chineses white pines (Pinus armandi Fr.) are the most important conifer species in Qinling Mountains, Northwest China, and main forestation species in upper and middle reaches of Yangtze River, China. But since the 50s of last century, P. armandi of Qinling Forest were damaged continuously by Dendroctonus armandi Tsai et Li, which led to a large number of deaths of healthy P. armandi at age over 30 years, and directly threatened the stability and sustainable development of Qinling forest ecosystem. Bark beetles have a high degree of selectivity on host trees. And they can use terpene volatiles from host trees to synthesize aggregation pheromones, etc, which enables the beetles to inbreak host trees with high density. So the selection mechanism of D. armandi, the composition and diffusion of host tree volatiles, etc, have became the keystone and focus to reveal the spatial dynamics and population diffusion of bark beetles. At present, diffusion dynamics of volatiles of P. armandi in Qinling Mountains have not been reported. This study was desigened to study the diffusion rules and temporal dynamic of volatiles from P. armandi in Qinling Mountains, which can reveal the distributing rules, temporal and spatial selection mechanism of D. armandi on host trees in Qinling forest ecosystem.In the study, the volatiles from needles and trunk phloem of healthy and attacked P. armandi were analysed through dynamic headspace adsorption method and gas chromatography-mass spectrometry (GC / MS) technology. And the results were as follows:1.The results identified that the volatiles from needles and trunk phloem of healthy and attacked P. armandi (including newly attacked wood, withered wood and dead wood in sequence) were six monoterpenes:α-pinene, camphene,β-pinene,β-myrcene, D-Limonene andβ-phellandrene.2. The monoterpenes change from needles of healthy and attacked P. armandi: the differences of relative content ofα-pinene,β-pinene,β-phellandrene were not significant in healthy and newly attacked trees; but along with the deepening of damage,α-pinene increased, whileβ-pinene andβ-phellandrene decreased in withered trees. Both of Camphene and D-limonene showed the highest relative content in newly attacked trees.β-phellandrene were not detected from needles in withered tree.3. The monoterpenes change from trunk phloem of healthy and attacked P. armandi: with the deepening of damage, the relative content of D-limonene increased gradually, while the content of the rest monoterpenes had no significant change in healthy and newly attacked trees. In withered and dead trees, the differences of the relative content ofα-pinene, camphene andβ-myrcene were not significant; butα-pinene, camphene increased over the previous two stages, whileβ-myrcene decreased; the relative content ofβ-pinene andβ-phellandrene were lower than the previous two stages and decreased in sequence.4. The relative content of monoterpenes between needles and trunk phloem of P. armandi had significant differences, whether in healthy trees, newly attacked trees or withered trees. This study showed thatα-pinene,β-pinene andβ-myrcene might be important signal substances that affected D. armandi to select different positions on host trees.5. the relative content ofα-pinene,β-pinene andβ-phellandrene had no significant differences in healthy and newly attacked trees. However with the deepending of damage from D. armand, in withered and dead trees, the content ofα-pinene was significantly higher, while the content ofβ-pinene andβ-phellandrene were significantly lower than the previous two stages. This rule might be related to weakness of healthy P. armandi affected by D. armandi and inducing secondary resistance of attacked P. armandi(Resin metabolism), also might be important signals of being attacked and weakness of D. armandi.
|
PDF Full Text Request