森林次生演替优势种苗木的光可塑性比较研究

本文从研究苗木的叶绿素含量和ＲｕＢＰ羧化酶活性随着光环境的变化而发生改变的规律出发，来探讨森林次生演替优势种苗木的光可塑性大小和对弱光环境的适应能力。各种苗木的叶绿素含量都随着光强度变弱而增加，但如果较长时间生长在弱光环境中，由于叶绿素的合成小于分解，其含量也会逐渐变小。不同的演替阶段优势种苗木的叶绿素含量的增加或减少在量上有一定的区别。以叶绿素含量随着光环境变化的测定值为指标，用模糊数学分析的结果表明，苗木的耐荫性大小顺序是演替后期种（黄果厚壳桂Ｃｒｙｐｔｏｃａｒｙａｃｏｎｃｉｎｎａ）＞演替过渡种（藜蒴Ｃａｓｔａｎｏｐｓｉｓｆｉｓａ）＞演替过渡种（荷木Ｓｃｈｉｍａｓｕｐｅｒｂａ）＞演替先锋树种（马尾松Ｐｉｎｕｓｍａｓｏｎｉａｎａ）；且藜蒴和荷木很接近，稍靠近黄果厚壳桂。马尾松和荷木的ＲｕＢＰ羧化酶活性随着生长环境的光强度的增加，其活性有所增加；但黄果厚壳桂的相应值是在每日直照光１ｈ的光环境中最高。除马尾松外，演替过渡种和后期种的苗木都是在每日直照光１ｈ的光环境中生长最好，这和每日短期照光提高ＲｕＢＰ羧化酶活性的（与没有直照光的环境相比较）同时又不分解叶绿素、不降低其含量有密切的关系。

THE COMPARATIVE STUDY ON PHOTO PLASTICITY OF THE DOMINANT SPECIES SEEDLINGS OF SECONDARY FOREST SUCCESSION

Based on the study of the variation of chlorophyll content and RUBISCO activity of seedlings in different photo habitats, this paper studied the photo plasticity and adaptability to forest shady of the dominant species seedling of secondary forest succession. The chlorophyll content increased as the illumination became weaker, but the chlorophyll content decreased, if the seedlings grew in weak illumination habitats for long time. But these variations were different among the dominant species seedlings in different forest successional stages. The results showed that the tolerant shade degrees were Cryptocarya concinna (late tree) > Castanopsis fissa (transitional tree) > Shima superba (also transitional tree)> Pinus massoniana (pioneer tree). The activity of RUBICO of Pinus and Shima increased as the illumination stronger. But the activity of RUBICO of Cryptocarya was the highest in 1 hour sunshine a day (like forest gap habitats). Middle and late successionals grew better in 1 hour sunshine a day habitat, except Pinus' seedlings. The tolerant shade seedlings could grow better in the forest gap habitats, because the sunshine could activate their activity of RUBICO, and the short sunshine didn't bleach the chlorophyll.