GEOGRAPHIC DISTRIBUTION LAW OF AVAILABLE SILICON IN SOILS IN THE STANDS OF PH. PUBESCENS IN ZHEJIANG AND FUJIAN PROVINCES

By the method of typical investigation on 172 profiles of the soil in major Ph. pubesccns forests in Zhejiang and Fujian Prov., 633 samples of soil were tesed to analyse the available Si content. The result showed the condition of the soil available Si content and its geographic region. It is indicated that the distribution of the soil available Si has a latitudinal zonality trend of increase from the south to north and a vertical zonality trend of increase from low to high altitude. Among the 3 kinds of rock, the soil available Si content was quite low in general igneous rock except for granite and tuff at higher elevation in this investigation. It, however, was comparatively high in sedimentary rock. But in metamorphic rock no significant trend appears. The order of the available Si content in soil was as the following:mountain yellow earch > calcareous soil > mountain yellow-brown earth > mountain red earth > yellow-red earth > acid purple soil > low hill red earth. Researching the typical profile, we found that the measures such as borrowing soil, cleaving grass etc. had great effect on the character of Si profile distribution in Ph. pubesccns stands. A distribution map of low available Si content was made so as to provide the information for the selection of the paper-pulp bamboo forest base.