摘要
利用自行设计的野外垂直照相装置 ,选择北京密云、怀柔的 2个样地对植被覆盖度进行动态监测 ,分析目估测量植被覆盖度的精度 .结果表明 :个人的目估覆盖度值很不可靠 ,不同人对同一块样点的目估结果存在显著差别 ,个人目估最大绝对误差可达到 4 0 % ;目估误差大小与目估对象的实际覆盖度大小有关 ,当实际覆盖度很大或很小时 ,目估绝对误差相对较小 ,反之则较大 ;随着参与目估人数的增加 ,多人目估均值的绝对误差相对个人目估明显有所减小 ,但这种误差减少程度的变化趋势却比较缓慢 ,2 0人目估均值的绝对误差仍可达到 10 %以上 。
Visual estimation is one of the most frequently used methods for plant coverage measurement,but estimation error is very great. The plant coverage of two fields located in Beijing is measured periodically in order to analyze the errors of eye measured plant coverage. The results show that the plant coverage estimated by different persons is very different and the maximal absolute error is about 40%. Estimation errors are related to actual plant coverage. They are greater under low or high plant coverage than those under the middle values of plant coverage. Although the average error of multiperson’s estimations for plant coverage is less than the individual estimation error the maximal absolute error of 20 persons’ estimated plant coverage is up to 10%. Using visual estimation method, plant coverage is over or under estimated by 10% to 40%. Therefore, this method should be used carefully.
出处
《北京师范大学学报(自然科学版)》
CAS
CSCD
北大核心
2001年第3期402-408,共7页
Journal of Beijing Normal University(Natural Science)
基金
国家杰出青年基金!资助项目 (4972 5 10 3)