Study on histories of old-growth forests and disturbances to them by fine scale pollen analysis of small hollows.

在日本西部奈良县odaiigahara和京都县Ashiu两处原生林的小洞中采集的花粉和木炭碎片数据明确了森林的历史及其受到的干扰。本研究表明，花粉分析对森林动态的研究是有益的。采用线性回归分析方法，分析了两种原生林冠层土壤表层花粉率与乔木率之间的关系。这些结果被用来解释来自小洞穴的化石花粉组合，作为林分尺度森林变化的记录。在小台原的Nanatsuike的山毛榉杉林的三个森林空洞中，花粉数据的比较表明了过去1300年的森林动态。在早期，长尾Chamaecyparis在森林中的比例高于现在。大约300年前，在这片山毛榉杉林的一个山谷附近，人们发现了一个缺口。落叶橡树侵入了这个空隙。此外，根据树木年轮，山谷附近的一棵落叶栎树已经有300岁了。同时增加的木炭碎片表明，缝隙形成的原因可能是闪电引起的小火。小台原町原町原的云杉林已经保存了1000年左右。在此之前，云杉在以落叶橡树为主的森林中是罕见的。对阿育县高吉达尼野生地一个岩心的花粉分析表明，在1000 ~ 500年这一时期，日本柳杉属为优势林，该时期柳杉属的花粉积累速率与现在的柳杉林基本相当。大约500年前以来，落叶栎和木炭碎片等次生林元素的树木增加。这些都与人为干扰有关。

Pollen and charcoal fragment data from small hollows made clear histories of forests and disturbances to them in the two old-growth forests, Odaigahara, Nara Prefecture and Ashiu, Kyoto Prefecture, western Japan. This study indicates that pollen analysis is useful for the study of the forest dynamics.1. Linear regression analysis was used to analyze a relationship between pollen percentage from surface layr of soil under a canopy and tree percentage in the two old-growth forests. These results were used to interpret fossil pollen assemblages from small hollows as a record of stand-scale forest changes.2. Comparison of pollen data from three forest hollows in a beech-fir forest at Nanatsuike in Odaigahara indicated forest dynamics for the last 1300 years. In the early stage, Chamaecyparis obtusa percentage in the forest was higher than that at present. A gap formation at about 300 years ago was recognized near one hollow in this beech-fir forest. Deciduous oak trees invaded into this gap. Also, a tree of deciduous oaks near the hollow was 300 years old based on its tree ring. Charcoal fragments that increased at same time indicated that the cause of the formation of the gap was possibly a small fire by lightning.3.A spruce forest at Masakigahara in Odaigahara has maintained for about 1000 years. Before then, spruce was rare in the forest that was dominated by deciduous oak.4.Pollen analysis of a core from the Chojidani Moor in Ashiu made clear that Crytomeria japonica was a forest dominant from 1000 yr.BP.to 500 yr.BP.Pollen accumulation rate of Cryptomeria in this period was almost equal to that of Cryptomeria forests at present. Since about 500 years ago, trees of secondary forest elements such as deciduous oak and charcoal fragments increased. These are associated with man-induced disturbances.