长白山阔叶红松林不同演替阶段土壤团聚体粒径组成及有机碳含量变化

阔叶红松林是我国东北重要的原生群落,其土壤团聚体在森林生态系统碳固定中具有重要作用.本研究采用空间代替时间的方法,选取白桦幼龄林、白桦中龄林、白桦成熟林、阔叶红松成熟林和阔叶红松过熟林5个不同演替序列,通过湿筛法研究长白山天然针阔混交林群落恢复演替中土壤团聚体粒径组成及有机碳含量的变化.结果表明: 土壤团聚体粒径组成受演替过程影响较大,不同演替阶段下土壤团聚体各粒级所占比例差异显著.团聚体平均质量直径随演替的进行表现为先升高再降低的单峰形式,且最高点出现在白桦成熟林阶段.土壤中不同粒级的团聚体内有机碳含量随着演替的进行呈先增加后略有下降的趋势,且团聚体内有机碳含量最大值出现在阔叶红松成熟林阶段.在同一演替阶段下,0～5和5～10 cm土层(除演替末期的阔叶红松过熟林外)中的各粒径团聚体内有机碳含量都随着粒径的减小而增加,而10～20 cm土层中的各粒径团聚体内有机碳含量都随着粒径的减小而减小.从演替初期的白桦幼龄林到演替末期的阔叶红松过熟林,每个样地内的同一粒径团聚体内有机碳含量均具有明显的垂直分布特性,均随着土层深度的增加而显著降低.

Changes of soil aggregate size composition and organic carbon content at different succession stages of broad-leaved Korean pine forest in Changbai Mountain,China.

The broad-leaved Korean pine forest is an important primary forest in Northeast China. Soil aggregates play important role in carbon fixation of forest ecosystem. Temporal-spatial substitution method was used in this study. We selected five forests with different succession stages: birch young forest, birch middle forest, birch mature forest, mature broad-leaved Korean pine fore-st, and over-mature broadleaved Korean pine forest. The distribution of soil aggregate particle size and agglomeration in organic carbon under different forests were investigated by wet sieving method. The results showed that soil aggregate size distributions and the proportions of soil aggregates were significantly different among succession stages. The mean mass diameter of aggregates was generally showed a unimodal trend along with the succession stages, peaking at birch mature forest stage. The organic carbon content in the aggregate of different particle-sizes in the soil increased firstly and then decreased slightly from early to late succession, and the maximum content of organic carbon in the aggregate was in broad-leaved Korean pine mature forest stage. Under the same succession stage, the content of organic carbon in the aggregate of different particle-sizes increased with the decreases of the particle size in the soil depth of 0 to 5 cm and 5 to 10 cm (except over-mature broad-leaved Korean pine forest at the end of succession), but it was the opposite in the soil depth of 10 to 20 cm. From the birch young forest at the early stage of succession to the over-mature broad-leaved Korean pine forest at the end of succession, organic carbon content in the aggregate of same particle-size had obvious vertical distribution characteristics, which significantly decreased with the increases of soil depth.