滇东南岩溶山地次生林土壤种子库储量与优势成分

Storage and dominants in soil seed banks under karst secondary forests in southeastern Yunnan

采用样线取样与温室萌发实验相结合的方法 ,调查了滇东南典型岩溶山地次生林的土壤种子库储量及其优势成分。结果发现 ,岩溶山地次生林下贮存有丰富的植物种子 ,在厚度为 1 0cm的表层土壤中的种子储量变动于 493 0～ 1 493 0粒 /m2 之间 ,高于对照成熟林的 3 780粒 /m2 。在 1 0cm的垂直剖面上 ,单位体积的种子储量在厚度为 0～ 2、2～ 5、5～ 1 0cm的三个层面间逐渐下降 ,但 5～ 1 0cm土层内仍然储藏了大量的种子。三种次生林的乔、灌、草、藤的比例组成与对照成熟林的差异不大 ,无论是种子个体数量还是物种种类数都以草本为主 (平均为 85 .5 %和 69.9% ) ,灌木次之 (平均为 1 2 .8%和 1 9.4% ) ,藤本 (平均为 1 .6%和 4.2 % )和乔木 (平均为 0 .6%和 6.5 % )稀少。在所研究的三个次生林样地内种子数量处于前三位的种子都来自菊科的紫茎泽兰 (Eupatoriumadenophorum) ,胜红蓟 (Ageratumconyzoides) ,劲直白酒草 (Conyzastricta) ,一点红(Emiliasonchifolia)等四个物种中的三个种 ,与成熟林下的土壤种子库中前三位物种基本相同。土壤种子库与地表植被间的相似性较小。

The storage and dominants of viable seeds in soil seed banks of the typical karst secondary forests in southeastern Yunnan were studied by using greenhouse germination methods and transect soil sampling method. There were abundant viable seeds stored in the soil seed banks under karst secondary forests. Seeds identified in soils at 10 cm depth ranged from 4 930 to 14 930 indi./m^2,higher than that of 3 780 indi./m^2 under a contrast matured karst forest. Vertically,the number of seeds per soil unit dropped down gradually from 0～2 cm depth,2～5 cm depth to 5～10 cm depth under secondary forests and matured forest. The composition of tree,shrub,herb and liana species differed slightly between secondary and matured forest. Herb species dominated the soil seed banks whether in terms of seed density or number of species identified (with average of 85.5% or 69.9% respectively). Shrub came next after herb species (with average of 12.8% or 19.4% respectively),liana (with average of 1.6% or 4.2% respectively) and tree (with averages of 0.6% or 6.5% respectively) species were rare. Among the three secondary karst forests studied,the top three species with higher seed percentage were three of the four Compositae species:Eupatorium adenophorum,Ageratum conyzoides,Conyza stricta,and Emilia sonchifolia,almost the same with that of matured forest. Low similarity in species composition was found between soil seed bank and the standing vegetation.