| Disturbance widely happens in forest communities. It drives and accelerates process of forest regeneration by germinating various environmental conditions. It is crucial for forest community to maintain its structure, diversity and stability. In sub-tropic montane forest, bamboos can quickly invade into forest gaps or other types of disturbed sites which are created by disturbance. Bamboos often dominate shrub layer in forest. They have deep impacts on the composition and structure of forest, impede forest regeneration and reducecommunity diversity.We selected sites in Jinfo Mountain where had several dwarf bamboo species. Firstly, we did a forest inventory to compared two types of forests. One forest was dominated by Fargesia decurvata and named F+. Another forest was dominated by Qiongzhuea communis and named Q+. We compared characteristics of the two dwarf bamboos. Then, we studied crown architecture of trees surviving in the F+, to explore their ecological strategies. Finally, we explored effects of dwarf bamboos on seed germination, seedling establishment and tree growth by removing dwarf bamboos. The major results were as follows:(1) The two bamboos differed in their characteristics. Height, leaf number, leaf area, first-order branching number and total biomass of Q. communis were significantly higher than that of F. decurvata. However, density and ratio of stem mass against total biomass of O. communis were significantly lower than that of F. decurvata. Furthermore. O. communis had a stronger interception on light and temperature. In addition, seedling and sapling abundance along with species richness were significantly higher in F. decurvata dominated forest than Q. communis dominated forest.(2)52quadrats were set up. Each quadrat included one shade sapling and one well-lit sapling at least. Crown size, shape and variables of branch were measured. Well-lit saplings had higher crown area and longer crown length crowns and more first-order branching number in terms of crown absolute size, but the two groups had similar crown shape and size when it came to ratio valuables. Shade plants would have greater changes in crown size scaling with plant height, stem diameter and branching number. At branch, shade plants produced less annual leaves but maintain more total leaf number at a given whole shoot length. In conclusion, shade saplings took the "lateral-growth strategy" to adapt the light-limited condition while well-lit saplings took the "vertical-growth strategy". Branch of shade saplings may took a "conservative strategy" which produced less annual leaves but maintain more total leaf number with longer lifespan at a given whole shoot length.(3) F. decurvatadid not affect the seed germination, but impeded the seedling establishment and enhanced seedling death. F. decurvata did not affect height and branch growth of saplings. However, saplings in the bamboo-removed sites, their leaf number of labeled branch were higher than that of saplings in bamboo-dominated sites. Growth of stem diameter was significantly higher in bamboo-removed sites. Meanwhile, apical stem of saplings in bamboo-removed sites died more than that of in bamboo-removed sites.The growth of seedlings and saplings was impeded in forest communities which were dominated by the dwarf bamboos. The dense bamboo layer changed environmental conditions, like light, which boost the death ratio of seedlings and saplings. Saplings were an important component of forest regeneration. The individuals acquired different growth strategies, such as, changing crown architecture to enhance light harvesting and sacrificing their annual apical stem, which adjusted themselves to the environment and alleviated the suppression of dwarf bamboos. |
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