云南阳宗海流域过去13000年植被演替与森林火灾

以云南阳宗海1020 cm长的湖泊沉积物岩芯为研究对象，由7个木屑和树叶残体样的AMS  ¹⁴C测年建立岩芯年代框架，以18~19 cm间隔获取52个样品作花粉/炭屑分析，重建了阳宗海流域过去13000年的植被、气候以及森林火灾历史。研究结果表明，过去13000年植被演替、气候变化和森林火灾可分为5个阶段：1）13200~11000 cal.a B.P.，植被以常绿、落叶阔叶混交林为主，气候温凉湿润，森林火灾多发，后期（12300~11000 cal.a B.P.）随着温度和湿度的降低，森林火灾发生愈加频繁；2）11000~8000 cal.a B.P.，松林扩张，阔叶林缩小，气候较上阶段温暖偏干，森林火灾发生次数明显降低；3）8000~5000 cal.a B.P.，松林和常绿阔叶林占优势，且出现暖热性的枫香林，流域内气温升至13000 cal.a B.P.以来的最高值，湿度进一步降低，但森林火灾发生频率低；4）5000~800 cal.a B.P.，松林扩张至最盛，常绿阔叶林收缩，落叶阔叶林成分增加，气温和湿度均明显下降，森林火灾发生频率有所增加；5）800 cal.a B.P.至今，松林和常绿阔叶林收缩，落叶阔叶成分增加，草本植物中禾本科迅速上升，可能与人类活动有关，森林火灾发生频率低。阳宗海花粉/炭屑记录重建的植被、气候和森林火灾史表明，在滇中地区，落叶阔叶成分易引起森林火灾，冷气候导致多发的森林火灾，冷干气候是宜森林火灾发生的气候条件。

VEGETATION SUCCESSION AND FOREST FIRES OVER THE PAST 13000 YEARS IN THE CATCHMENT OF YANGZONGHAI LAKE,YUNNAN

The pollen/charcoal analyses of 52 samples from a 1020-cm core(YZH-1:24°54'42"N,103°0'7"E)taken from Yangzonghai Lake(24°51'24"~24°57'58"N,102°58'47"~103°01'41"E)in Yunnan were conducted to reconstruct the historical records of vegetation,climate,and forest fires in the catchment of Yangzonghai Lake.The age-depth model for this core was established using 7 AMS14C dates obtained from wood and leave remains.Our results reveal five stages of vegetation succession,climate change,and forest fires over the past 13000 years.(1)13200~11000 cal.a B.P.,vegetation was dominated by evergreen and deciduous broadleaved mixed forest indicating cool and wet conditions,frequent forest fires occurred frequently,especially the temperature and humidity decreased at its late interval from 12300 cal.a B.P.to 11000 cal.a B.P.,this period aslo corresponds to the Younger Dryas climate event;(2)11000~8000 cal.a B.P.,pine forest expanded and broadleaved forest shrank,showing warmer and drier conditions than at the preceding stage,and the occurrence of forest fires decreased;(3)8000~5000 cal.a B.P.,the catchment of Yangzonghai Lake was occupied by pine forest and evergreen broadleaved forest together with Liquidambar forest,suggesting a warm and relatively dry conditions;temperature rose to the highest over the past 13000 years,and humidity was lower than that of the previous stages but it was still higher than the present;the forest fire frequency was low;(4)5000~800 cal.a B.P.,an expansion of pine forest to its maximum together with a shrinkage of evergreen broadleaved forest and an increase in deciduous broadleaved elements shows a significant drop in temperature and humidity,and a little bit more forest fires occurred than at the preceding stage occurred in this period;(5)800 cal.a B.P.to the present,deciduous broadleaved forest elements and upland herbaceous plants increased at the cost of pine forest and evergreen broadleaved forest,suggesting increasing human activities,the forest fire frequency was low;however,the temperature dropped and humidity increased at the interval of 800~460 cal.a B.P.,probably implying the occurrence of Little Ice Age in central Yunnan;then the humidity decreased as the temperature rose from 460 cal.a B.P.to the present.Thus,the climate in Yangzonghai Basin have successively undergone the period of warm/cool and humidity,warmer and dry,warmest and dry,cold and dry,and colder and dry during the past 13000 years.Our reconstruction of vegetation,climate,and forest fire changes also indicate that,deciduous broadleaved forest materials easily cause forest fires,cold conditions result in frequent forest fires,and a combination of cold and dry conditions is the primary cause of forest fires in central Yunnan.