寒温带兴安落叶松林土壤团聚体特征及其影响因素研究

以寒温带兴安落叶松(Larix gmelinii)林为研究对象,分析其土壤团聚体的分布及其有机碳含量特征,并探讨各土壤因子对团聚体稳定性的影响。在兴安落叶松林内设置28块30 m×30 m的样地,以0—10、10—20、20—40、40—60 cm分层取土样,测定各理化指标含量、不同粒级土壤团聚体及其有机碳含量。结果表明,兴安落叶松林土壤团聚体各粒级含量高低为(0.25—2 mm粒径)团聚体>(<0.053 mm粒径)团聚体>(0.053—0.25 mm粒径)团聚体,各粒级团聚体表层(0—10 cm)含量均显著区别于其他各层;土壤团聚体的平均质量直径(MWD)、几何平均直径(GMD)分别为0.53 mm和0.22 mm,分维数(D)为2.78,土壤团聚体稳定性较高且存在剖面差异;土壤有机碳主要分布于0.25—2 mm粒径的大团聚体中(34.51g·kg^-1),贡献率为52.10%,粒径0.053—2 mm土壤团聚体中有机碳含量最低(6.30 g·kg^-1),贡献率为16.42%;随土层深度增加,各粒级团聚体有机碳含量和0.25—2 mm团聚体有机碳贡献率逐渐减小,<0.25 mm团聚体贡献率逐渐增大,40 cm以下各粒级贡献率趋于稳定;兴安落叶松林土壤团聚体的粒径分配和稳定性受到林龄和林型的显著影响;大团聚体(0.25—2mm)含量与土壤总有机碳(SOC)呈极显著正相关关系(P<0.01),微团聚体(<0.25 mm)含量与Al、Mg等金属氧化物含量呈显著正相关关系(P<0.05);大团聚体(0.25—2 mm)含量和MWD、GMD指标与pH值呈极显著负相关关系(P<0.01),与土壤含水量、速效钾、有效磷、有机磷呈显著正相关关系(P<0.05)。综上,土壤有机质和金属氧化物分别为兴安落叶松林土壤0.25—2 mm大团聚体和<0.25 mm微团聚体的主要胶结物质,土壤水分、养分和酸碱条件对团聚体的形成和稳定产生影响。

Characteristics of Soil Aggregates and Its Influencing Factors in Larix gmelinii Forest in Cold Temperate Zone

Taking Larix gmelinii forest in cold temperate zone as the research object,the distribution of soil aggregates and the characteristics of its organic carbon content were analyzed,and the effects of soil factors on the stability of soil aggregates were discussed.28 plots of 30 m×30 m were set up in Larix gmelinii forest.Soil samples were collected in layers of 0–10 cm,10–20 cm,20–40 cm and 40–60 cm above the ground.The physicochemical indexes,soil aggregates and its organic carbon content were determined in the laboratory.The results showed that soil aggregates content in Larix gmelinii forest followed the order of(0.25–2 mm)aggregate>(<0.053 mm)aggregate>(0.053–0.25 mm)aggregate.The aggregate content in surface layer(0–10 cm)was significantly different from that of other layers.The mean weight diameter(MWD)and geometric mean diameter(GMD)of soil aggregates was 0.53 mm and 0.22 mm,respectively,and fractal dimension(D)was 2.78.The soil aggregate stability was high and there were differences in profile.Soil organic carbon(SOC)was mainly distributed in 0.25–2 mm macroaggregates(34.51 g·kg^?1)with contribution rate of 52.10%.The organic carbon content of 0.053–2 mm aggregates was the lowest(6.30 g·kg^?1)with contribution rate of 16.42%.With the increase of soil depth,the organic carbon content of aggregates in all particle sizes and the contribution rate of 0.25–2 mm aggregates decreased gradually,the contribution rate of<0.25 mm aggregates increased gradually,and the contribution rates of all fractions tended to be stable in the depth of below 40 cm.The distribution and stability of soil aggregates in Larix gmelinii forest was significantly affected by forest age and forest type.The macroaggregate(0.25–2 mm)was significantly positively correlated with SOC(P<0.01),the microaggregates(<0.25 mm)was significantly positively correlated with Al,Mg and other metal oxides(P<0.05).The content of macroaggregate(0.25–2 mm)and MWD,GMD were significantly negatively correlated with pH value(P<0.01),and significantly negatively correlated with soil water content,pH,available potassium,available phosphorus and organic phosphorus(P<0.05).It indicated that soil organic matter and metal oxides were the main cementation materials of 0.25–2 mm macroaggregate and<0.25 mm microaggregate in Larix gmelinii forest soil,respectively.Soil moisture,nutrient and acid-base conditions had an impact on the formation and stability of soil aggregates.