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

来自小洞穴的花粉和木炭碎片数据清楚地记录了日本西部奈良县大田原和京都县阿修这两个古老森林的森林历史及其受到的干扰。这项研究表明，花粉分析对森林动态的研究是有用的。采用线性回归分析方法，对两种老树林下土壤表层花粉含量与成株率的关系进行了分析。这些结果被用来解释来自小山谷的化石花粉组合，作为林分尺度森林变化的记录。对大田原南津池山毛榉-冷杉林中三个森林空穴的花粉数据进行了比较，表明了过去1300年的森林动态。在早期阶段，林木中钝顶木虱的百分率高于现在。在这片山毛榉-冷杉林的一个凹地附近发现了一个大约300年前形成的空隙。落叶橡树侵入了这个空隙。此外，根据树轮，洞穴附近的一棵落叶橡树已有300年的历史。同时增加的木炭碎片表明，形成林隙的原因可能是雷击造成的小火。3.小田原Masakigahara的一片云杉林已经维持了大约1000年。在此之前，落叶栎林中云杉稀少。4.对阿修乔吉达尼荒原的一个岩心的花粉分析表明，柳杉在1000年至500年期间为优势林。这一时期柳杉的花粉积累速率与目前柳杉森林的花粉积累速率几乎相等。自约500年前以来，次生林成分如落叶栎木和木炭碎片的树木增加。这些都与人为的干扰有关。

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.