滇中阳宗海流域过去1200年以来的环境变化

根据滇中阳宗海78 cm沉积岩芯的花粉/炭屑分析,重建了阳宗海流域过去1200年的植被演替、气候变化和森林火灾史。岩芯年代框架的建立基于底部一个植物残体的AMS14C测年和上部的210Pb测年。结果表明:1)阳宗海流域过去1200年的植被变化经历了4个阶段:暖干期(780—1630 AD)的植被以松栎混交林为主,草本植物少;凉湿期(1630—1860 AD)的植被仍以松栎混交林为主,但比重有所减少并存在明显波动,草本植物显著增加;冷干期(1860—1950 AD)和随后的暖干期(1950 AD之后)受人类活动干扰强烈,人类活动可能已成为影响植被的主导性因素。2) 1200年以来,阳宗海流域气候变化存在明显的暖期(780—1630 AD)和冷期(1630—1950 AD),分别对应了中世纪暖期和小冰期,且水热条件配置呈现暖干-冷湿的模式,与滇西天才湖、洱海和青藏高原东部等邻近区域较为同步。整个暖期气温波动不大,仅在最暖的12世纪中期到15世纪中期温度表现出较大的波动,小冰期存在两个气候波动阶段,分别是1630—1860 AD凉湿期和1860—1950 AD的冷干期。阳宗海流域气候变化的主...

Environmental changes over the past 1200 years in the catchment of Yangzonghai Lake,Central Yunnan.

We carried out pollen/charcoal analyses on sediments of a 78-cm core from Yangzonghai Lake to study vegetation succession,climatic change,and forest fire history over the past1200 years in the catchment of Yangzonghai Lake,central Yunnan.The age-depth framework was established using an AMS14 C dating of plant remnants at the bottom and210 Pb dating at the top.The results showed that:(1)There were four stages of vegetation changes in the catchment of Yangzonghai Lake over the past 1200:the first one was a warm and dry stage(780-1630 AD),when vegetation was dominated by mixed forest of pine and oak with few herbs;the second stage was a cool and wet stage(1630-1860 AD),when vegetation was still dominated the mixed forests of pine and oak,but with a decrease in the forest proportion and substantial fluctuations,and with a significant increase in herb proportion;it was followed by a cold and dry stage(1860-1950 AD)and the subsequent a warm and dry stage(after 1950 AD),when vegetation was strongly disturbed by human activities,which may have become the dominant factor driving vegetation.(2)Across the past 1200 years,a warm period(780-1630 AD)and a cold period(1630-1950 AD),corresponding to Medieval Warm Period and Little Ice Age respectively,occurred in the catchment of Yangzonghai Lake.Moreover,the hydrothermal conditions showed a pattern of warm-dry and cold-wet,which occurred almost synchronously in the adjacent areas such as Tiancai Lake and Erhai Lake in northwest Yunnan and eastern Qinghai-Tibetan Plateau.During the whole warm period,temperature was stable with a little bit more fluctuation in the warmest stage from the middle of the 12 th century to the middle of the 15 th century.Climate during the Little Ice Age showed two periods,namely a cool-wet period from 1630 to 1860 AD and cold-dry period from 1860 to 1950 AD.The dominant forcing of climate change over the past 1200 years in the catchment of Yangzonghai Lake was solar forcing associated with regional and global oceanatmosphere coupling.(3)Forest fire increased gradually over the past 1200 years in the catchment of Yangzonghai Lake,a trend consistent with population growth and human activities,indicating that human activities have gradually become one of the dominant driving forces of environmental change.