图1. 大兴安岭北部不同林龄白桦林土壤层碳含量(平均值±标准偏差)。不同大写字母表示同一林龄不同土层间差异显著, 不同小写字母表示同一土层不同林龄间差异显著(p < 0.05)。

Fig. 1. Carbon content of soil layer in the Betula platyphylla forests of different ages in the north section of the Da Hinggan Ling Mountains, NE China (mean ± SD). Different capital letters indicate significant differences among different levels of the components of the forest of same age, and different lowercase letters showed significant differences among the same type of component, but different forest ages (p < 0.05).