不同林龄杉木人工林土壤团聚体及其有机碳变化特征

土壤团聚体作为土壤结构性状的重要指标,对土壤孔隙、持水、保水等状况都有重要影响;土壤团聚体有机碳除了反映土壤固碳状况外,还与团聚体的稳定性能密切相关,研究森林土壤团聚体及其有机碳状况,旨在为合理利用土壤、提高人工林水源涵养功能提供依据。为此,以福建省洋口国有林场不同林龄杉木人工林(幼龄林、中龄林、成熟林)土壤为研究对象,通过野外调查、采样和室内分析,研究不同林龄杉木人工林土壤团聚体及其有机碳变化特征。结果表明:不同林龄杉木人工林对土壤团聚体及其有机碳具有重要影响,成熟林土壤大团聚体含量、团聚体平均重量直径(MWD)、团聚体有机碳含量及贡献率均分别大于幼龄林、中龄林;不同林龄的土壤水稳性团聚体均以大团聚体(粒径0.25 mm)为主,占59.57%～80.97%,粒径0.053 mm的仅占0.80%;土壤团聚体有机碳贡献率也以大团聚为主,其中以2～0.25 mm粒级贡献率最高,达58.43%;另外,土壤有机碳含量与团聚体MWD呈显著正相关,且具有明显的垂直变化特征,即随土层加深而下降。因此,土壤有机碳对团聚体稳定性具有积极作用,不同林龄土壤团聚体稳定性及有机碳变化规律为成熟林幼龄林中龄林。

Changes of Soil Aggregates and Its Organic Carbon in Chinese Fir Plantations with Different Forest Ages

As an important indicator for soil structure, soil aggregates have a huge impact on soil porosity and water holding capacity. Soil aggregate organic carbon can not only reflect soil carbon sequestration capacity, but also be closely related to aggregate stability. Study on soil aggregates and organic carbon distribution characteristics in Chinese Fir plantations can provide theoretical basis for improving soil productivity and water use efficiency. In our research, soil samples were collected from Chinese Fir plantations with different forest ages (6, 11 and 32 years), which was located in Yangkou National Forest Farm, Fujian Province, China. The water-stable soil aggregate composition and organic carbon contents were measured. The results showed that forest age was very important in terms of soil aggregate and its organic carbon. Macro-aggregate contents (>0.25 mm), MWD, organic carbon contents and its contribution of aggregates in mature forest were higher than that in young and middle forests. Water-stable macro-aggregates were the main part of soil aggregates, which accounting for about 59.57%~80.97%, while the aggregates with the partical size less than 0.053 mm only accounted for 0.80%. In terms of organic carbon contribution, macro-aggregates were the main contributor, and aggregates with the partical size 2~0.25 mm accounted for 58.43%. Furthermore, soil aggregate MWD and its carbon content had a typically vertical characteristic, decreasing with soil depth. A strong positive correction was found between aggregate MWD and organic carbon. Hence, organic carbon was beneficial for the stability of soil aggregate, and MWD and organic carbon contents of aggregate showed a trend as mature forest > young forest > middle forest.