摘要
作为火的代用指标-炭屑在过去生态环境变化及人类活动研究中具有重要意义,基于孢粉学方法开展的微体炭屑-火的研究得到了研究者的广泛关注,但关于炭屑统计的标准目前尚未统一。通过选取黄土高原灵台剖面顶部13 m共16个样品,采用孢粉流程法提取炭屑(外加石松孢子以计算炭屑浓度),对样品进行随机分组统计。具体方法如下:统计时以50粒外加石松孢子为单组,每个样品累计统计20组,且每组中按形态(长宽比)分为长条形炭屑与近圆形炭屑,按大小划分为10~30μm,30~50μm,50~100μm和>100μm共4种粒级。结果表明20个单组中炭屑含量相近但有一定波动性(标准偏差0.06%~8.70%);当石松孢子累计统计500粒(10组)以上时,炭屑浓度、各粒径炭屑所占百分比均趋于稳定(相关系数r=0.99);当石松孢子累计统计300粒(6组)以上时,炭屑的长/圆比值趋于稳定(标准偏差0.01~0.24,r=0.87)。基于以上结果,建议在黄土高原微体炭屑研究中统计500±50粒的石松孢子,以确保数据稳定。以此为基础,初步发现灵台地区自165 ka以来,火事件较为频繁,草本较木本植被更占优势,此结果与该地区黄土-古土壤中元素碳含量等数据有较好对应关系,表明该地区的古火发生与环境变化具有较强联系。
Fire plays an important role in studies of paleoclimate change and human activities.Microcharcoal in sediments can indicate the extent,frequency and variation of wildfires throughout geological history.Studies of microcharcoal fires based on pollen methodologies have received extensive attention from researchers,however,statistical approaches to lycopodium spores related to the needs of sporopollen statistics are uncertain,and this may result in the instability of results of microcharcoal.The Lingtai(LT)profile(33°04′N,107°39′)chosen for this study is located in Lingtai County,Gansu Province,China.16 samples from different layers were selected throughout the 13 m profile(S 0~L 2),nine of which were in the loess layers and seven in the paleosol layers.All samples were extracted by a standard pollen methodology(adding a known number of lycopodium spores to each sample in order to calculate microcharcoal concentrations).To obtain the number of lycopodium spores that should be counted in microcharcoal research,20 groups were counted for each sample and 50 lycopodium spores for each group,giving a total of 1000 lycopodium spores.Two distinct shapes of microcharcoal were identified:sub-round(length/width<2.5,R)and sub-long(length/width>2.5,L),which respectively represent woody and herb sources.The data were then divided into four groups of grain-size groups:~10-30μm,~30-50μm,~50-100μm,and>100μm.Results showed that the percentages and concentrations of microcharcoal in the 20 groups studied were similar but exhibited some fluctuation(standard deviation:0.06%~8.7%).We compared the data from the first accumulating group(i.e.,one group)to the twentieth accumulating group(i.e.,a total of twenty groups),finding that when the total number of lycopodium spores is greater than 500,the accumulated microcharcoal concentration in each sample no longer shows significant change,and the percentages of each grain-size group tend to be stable.When the total number of lycopodium spores is 300 or greater,L/R ratios tend to be s
作者
王梓莎
赵永涛
苗运法
邹亚国
唐国乾
WANG Zi-sha;ZHAO Yong-tao;MIAO Yun-fa;ZOU Ya-guo;TANG Guo-qian(Northwest Institute of Ecology and Environmental Resources,Chinese Academy of Sciences,Lanzhou 730000,Gansu,China;University of Chinese Academy of Sciences,Beijing 100049,China;School of Resources and Environmental Sciences,Lanzhou University,Lanzhou 730000,Gansu,China)
出处
《干旱区地理》
CSCD
北大核心
2020年第3期661-670,共10页
Arid Land Geography
基金
国家自然科学基金(41772181、41807440)
黄土与第四纪地质国家重点实验室开放基金(SKLLQG1515)
甘肃省自然科学基金(18JR3RA395)
国家“万人计划”青年拔尖人才
中科院‘西部之光’和中科院青年创新促进会优秀会员(2014383)资助。
关键词
黄土高原
炭屑统计
古火
环境变化
Loess Plateau
microcharcoal statistics
paleo-fire
environmental change
