亚热带常绿阔叶林不同演替阶段土壤种子库的初步研究

A PRELIMINARY STUDY ON THE SOIL SEED BANKS OF DIFFERENT SUCCESSIONAL STAGES OF SUBTROPICAL EVERGREEN BROADLEAVED FOREST

本文把四川缙云山亚热带常绿阔叶林的演替系列分成6个阶段:(1)弃耕地;(2)灌草丛;(3)马尾松林;(4)以马尾松为优势的常绿针、阔叶混交林;(5)以常绿阔叶树为优势的针、阔叶混交林;(6)常绿阔叶林。分别从每个阶段分3层采集0.5m^2,10cm厚度的5个小样地的土样,带回实验室,通过萌发法研究土壤种子库。得到如下结论:A、种子数量和物种多样性在演替早期阶段(从弃耕地到马尾松林)一般随演替发展而减少,种子数目随土层加深而降低;后期阶段(马尾松林到常绿阔叶林)种子数则大致随演替发展而增加;同一阶段各土层种子数差异不大。B、各演替阶段土壤种子库的种类组成均以草本植物为主。C、在湿度和光照比较一致的情况下,萌发种子数与温度成正相关。大多数种类的种子80％以上在实验的头六个星期内萌发。D、演替早期阶段的地上植物种类组成与土壤种子库中种类组成基本一致,演替后期阶段相关甚少。本文还讨论了土壤种子库研究的取样体积问题,以及土壤种子库在植被动态中的作用。

The successional series of subtropical evergreen broadleaved forest in Jinyun Mountain of Sichuan province has been divided into six stages in this paper. They are: (1) old-field; (2) shrub grassland; (3) masson pine forest; (4) evergreen needle and broadleaved mixed forest dominated by masson pine; (5) needle and broadleaved mixed forest dominated by evergreen broadleaved species; (6) evergreen broadleaved forest. Five 0.5m^2 soil sample measured 10cm high from each of six stages were taken to laboratory to let seeds in the soil germinating. From the appearance of seedlings, we concluded followings: A. At the early stages of succession (from old-fieds to masson pine forest), the number of seeds and species diversity decreased with the development of succession. In these stages, the deeper the soil stratification is, the less the number of seeds is. At the later stages of succession(from masson pine forest to evergreen broadleaved forest), the number of seeds is increased with succession evolution. In different stratification of same stage, the number of seeds is nearly the same. B. Most of seeds in different stages are herb species. C. If humidity and light is fixed, the number of germinated seeds is interrelated with temperature. More than 80% seeds of most species are germinated in six weeks. D. The species composition between above ground vegetation and soil seed banks are nearly the same at the early stages of succession, but it is very different in the later stages.The sampling volume of soil seed banks and the signification of soil seed banks in vegetation succession have also been discussed in this paper.