不同林龄云南松人工林土壤腐殖质的组成分析

为了解不同林龄阶段人工林土壤腐殖质化学组成和结构特征的差异,以云南松人工纯林为研究对象,利用土壤化学分组及傅里叶变换红外光谱等研究手段,对土壤胡敏酸(HA)和富里酸(FA)的结构特征进行分析.结果表明,随着造林时间增加,土壤p H呈下降趋势,造林年限增加27年,土壤p H下降0.6个单位.幼林阶段土壤C,C/H高于中龄林和成熟林阶段,而土壤N,H,C/N随造林年限增加变化不大.各林龄阶段表层土壤C,N,C/N,C/H普遍高于表层以下土壤.红外光谱分析表明,云南松人工林土壤HA和FA具有相似的化学结构及官能团组成,主要含有酚羟基、芳香基、脂族烃基、羧基等基团.从造林年限变化趋势看,从幼林到成熟林阶段,土壤表层HA中小分子糖类物质减少,芳香类物质增加,说明造林年限增加土壤HA结构变得复杂.土壤FA随造林年限的变化特征与HA相似,但其表层(0~20 cm)土壤中羧基含量增加十分明显,说明表土羧酸类物质有随林龄增加的趋势,这可能是引起造林后期土壤p H下降的原因之一.从剖面深度看,随土层增加,土壤HA和FA中小分子糖类物质呈降低趋势,而芳香类物质含量增加,说明人工林深层土壤腐殖质的化学稳定性高于表土层.

Composition analysis of soil humus in Yunnan pine plantation at different stand ages

To understand the differences of chemical composition and structure characteristics in plantation soil humus with different ages, humic acids (HA) and fulvic acids (FA) in Yunnan pine plantation were studied by chemical fractionation, elemental analysis and Fourier transform infrared spectroscopy (FTIR). The results indicated that the soil pH decreased with the increase of afforestation time. When the afforestation time increased by 27 years, the pH of soil has decreased by 0.6 units. The C and C/H ratio of soil in young forest stage were higher than those eihter in middle-aged forest or mature forest, while N content, H content and C/N ratio in soil changed little with increasing stand age. Generall, at the same afforestation age, the C content, N content, C/N ratio and C/H ration in surface soil were higher than those in deep soil. The FTIR analysis indicated that the HA and FA in Yunnan pine plantation soil showed similar chemical structure and functional groups, and thery were mainly phenolic hydroxyl group, aromatic group, aliphatic hydrocarbon group, carboxyl group, et al. With the extension of afforestation time, the content of carbohydrate of HA in surface soil decreased, and the amount of aromatics increased, suggesting the HA in soil became complicated and refractory. The content of carboxyl groups of FA in surface soil (0-20 cm) showed obvious increasemnet with the extension of afforestation time, which could further result in the decrease of soil pH. When the soil depth rose up, the content of small molecule carbohydrate in HA and FA of soil was gradually decreased, while the content of aromatic substances showed increased trend. The results indicated chemical structure of soil humus in plantations soil was more stable than that in surface soil.