微炭屑的几种统计方法比较及其对人类活动的指示意义

微炭屑是研究火的历史和过去人类活动、重建古生态的一项重要指标。它一般指长轴小于120μm、黑色不透明的炭化颗粒。常用点接触法（11刻点和202刻点）、图像识别法、颗粒计数法和分粒级法进行微炭屑统计。本文利用不同方法求得的微炭屑面积浓度或颗粒浓度曲线显著相关，相关系数在0.6以上（p<0.05），表明这几种方法的微炭屑统计结果具有相似的变化趋势，尤其是两种点接触法与图像识别法的统计结果更加相近，相关系数分别为0.79与0.88；  颗粒计数法与点接触法、图像识别法的相关系数是0.75和0.74。分粒级法与点接触法、图像识别法和颗粒计数法的相关性随着粒级的变化而不同。两种点接触法的微炭屑统计结果的相关系数高达0.93，反映了这两种方法所得微炭屑统计结果具有几乎相同的变化趋势。202刻点接触法由于与其他统计法的相关性都比较高，统计视域多且鉴定统计速度快，是进行微炭屑统计的最佳方法。微炭屑浓度高的时段出现在繁荣的文化期，可能指示着强烈的人类活动。

COMPARISON OF DIFFERENT QUANTIFICATION METHODS FOR MICROFOSSIL CHARCOAL CONCENTRATION AND THE IMPLICATION FOR HUMAN ACTIVITIES

Microfossil charcoal is one of the important proxies for exploring fire history and ancient human activity. It is generally identified as being black,opaque and angular with a size smaller than 120μm.Five different quantification methods including touch point-counts,computerized imaging technique,particle counting,size-classes are employed to estimate the microfossil charcoal concentration. A comparison study shows that the results obtained with different quantification methods are significantly correlated(F-value>0.7,p-value<0.05)and display similar trend of change. The two touch point-counts methods(11 touch point-counts and 202 touch point-counts)have a particularly high correlation coefficient(F-value 0.93).By comparison,the correlation coefficient of touch point-counts and computerized imaging technique is 0.88.The coefficients between the size-classes and other quantification methods are found to vary with the particle size of the microfossil charcoal. The 202 touch point-counts method is considered to be a better method for quantifying microfossil charcoal as it has high coefficients with other methods,smaller error and costs less counting time. The peak values of microfossil charcoal for these quantification methods are shown to coincide with the period of prosperous cultures and indicate strong human activities.