| Leaf functional traits can reflect the adaptive strategies of plants to different environments.Plant invasions often produce competitive stress on native plants and change leaf functional traits.In recent years,the utilization rate of bamboo forests has decreased and a large area of bamboo has been abandoned.However,bamboo has a strong ability to expand,easily expanding into its adjacent Chinese fir forest,causing harm to the ecosystem and biological community and showing similar characteristics to invasive species.However,the dynamic response strategy of leaf functional traits of Chinese fir to bamboo expansion is not clear.Chinese fir in the pure Chinese fir forest,bamboo and Chinese fir mixed forest and Chinese fir released forest after bamboo removal were studied.The seasonal variation characteristics and correlations of leaf functional traits of Chinese fir and soil physical and chemical properties were studied by using spatio-temporal substitution method and removal experiment.The results show that:(1)Compared with pure Chinese fir forest,leaf thickness,leaf relative water content,leaf morphology index,leaf carbon content,leaf nitrogen content,leaf phosphorus content and anatomical tissue thickness,and seasonal average chlorophyll content of Chinese fir in the mixed forest decreased,while leaf water saturation deficit increased.The plasticity index of leaf functional traits of most Chinese fir in mixed forest was low.Soil available phosphorus content and available kalium content also showed a decreasing trend in mixed forest.The results showed that the expansion of bamboo weakened the water and nutrient retention ability of Chinese fir,decreased the photosynthetic ability,and decreased the soil nutrient content in the forest,which made Chinese fir lack of competitiveness and was not conducive to the growth and development.(2)Compared with pure Chinese fir forest,leaf tissue density and leaf kalium content of Chinese fir in the mixed forest increased,specific leaf area decreased in spring and autumn,and chlorophyll content increased in growth season.The results showed that Chinese fir would try to adapt to the stress environment through character changes during the competition with bamboo,so that it could maintain certain growth in the mixed forest where bamboo was dominant.(3)Compared with pure Chinese fir forest,the leaf tissue density,cuticle thickness,epidermis thickness and sponge tissue thickness of Chinese fir increased,and the leaf morphology index,leaf carbon content and average seasonal chlorophyll content decreased in the Chinese fir released forest after bamboo removal.Soil moisture content increased,total nitrogen content and available phosphorus content decreased.The results showed that the nutrient retention and photosynthetic capacity of remaining Chinese fir were improved after bamboo removal,and the suppression of Chinese fir growth had been alleviated.However,the leaf functional characters of Chinese fir and soil physical and chemical properties had not recovered significantly compared with pure Chinese fir forest because of bamboo removal time is shorter.(4)There was a close correlation between leaf functional traits of Chinese fir and a certain correlation between leaf functional traits of Chinese fir and soil physical and chemical properties.In conclusion,although bamboo expansion inhibits the growth of Chinese fir,but Chinese fir leaves can adapt to the competition of the larger environment through adjusting function traits.These results indicated that the leaf functional traits of Chinese fir had a response strategy to bamboo expansion.It can provide scientific basis for further reasonable regulation of bamboo expansion and restoration of degraded forest ecology. |
