根据冲积物孢粉恢复冀北山地古植被的意义

ANCIENT VEGETATION INTERPRETED BY ALLUVIAL POLLEN AT NORTHERN MOUNTAIN AREA OF HEBEI PROVINCE

冲积物是第四纪孢粉分析经常遇到的研究对象。冲积物孢粉研究表明，晚全新世以来，人类活动是影响冀北山地植被演变的主要因素。人类活动对白河流域森林植被的破坏可能较早；对潮河流域森林植被的破坏较晚。

Alluvial sediments are frequently used in Quaternary pollen studies. There are obviously differences in pollen deposition and sedimentation between alluvial pollen and lacustrine and peat pollen. There were no great changes in vegetation types in northern mountain area of Hebei Province since the Late Holocene. The major factor is that mankind caused the vegetation change. It was probable that human destroyed the forest vegetation earlier in the Baihe River drainage. The vegetation cover at the time of 2400 a B.P. was similar to that of the present . The forest vegetation was destroyed later in the Caohe River drainage, with higher forest cover (about 40-50%) than that of present at the beginning of the Late Holocene. After about 1200 a B.P., forest vegetation destroyed seriously and changed into that of the present quickly by the increasingly influences of the human activities.