南亚热带杉木人工成熟林密度对土壤养分效应研究

目的]研究5种不同密度林分土壤剖面养分含量的变化规律。方法]以广西大青山37年生杉木密度试验林为研究对象,测定了A(1 667株·hm-2)、B(3 333株·hm-2)、C(5 000株·hm-2)、D(6 667株·hm-2)、E(10 000株·hm-2)5种密度下0 100 cm土层土壤养分含量。利用单因素方差分析和多重比较判断不同密度和不同土层土壤养分含量的差异。结果]表明:(1)杉木人工成熟林大多数土层土壤有机质、全氮、碱解氮、全磷、有效性铁含量在A、B等低密度林分中最高,并且在0 30 cm的土壤中,随密度的增加表现出总体下降的变化趋势,而土壤pH值与全钾、速效钾随密度的增加而上升,交换性钙与交换性镁含量受密度影响不明显;(2)土壤有机质、全氮、碱解氮、有效磷、速效钾、交换性钙、交换性镁和有效性铁含量均随土层深度的增加而明显下降,0 30 cm表层土壤的降幅较大,密度对不同土壤深度养分含量的变化具有一定影响。结论]初植密度对杉木人工成熟林土壤养分含量影响明显,低初植密度更有利于杉木人工林土壤肥力的长期维持,南亚热带杉木林密度对土壤养分的影响深度可达60 cm。

Effect of Stand Density on Soil Nutrient of Chinese Fir Mature Plantations in South Asia Subtropical Zone

Objective] To study the effect of five initial planting densities and different soil profile on soil nutrient contents of Chinese fir (Cunninghamia lanceolata) mature plantation. Method] The soil nutrient contents (0-100 cm soil layers) of C. lanceolata mature plantation in Daqingshan Forest Farm under five different planting densities of A (1 667 trees·hm^-2), B (3 333 trees·hm^-2), C (5 000 trees·hm^-2), D (6 667 trees·hm^-2), and E (10 000 trees·hm^-2) were measured. One-way ANOVA and the least significant difference were applied to determine the soil nutrient contents in different densities and different soil layers. Result] The results showed that: (1) The contents of organic matter, total N, P, available N and available Fe were the highest in most soil layers of stands with density A or B. In general, as initial planting density increased, the contents of organic matter, total N, P, available N and available Fe in upper soil layers (0-30 cm) decreased. While soil pH, total K and available K increased with initial planting density. Moreover, the initial planting density did not significantly influence the contents of exchangeable Ca and Mg; (2) Soil organic matter, total N, available N, P, K, exchangeable Ca, Mg and Fe contents obviously decreased with increasing soil depths. This pattern was particularly evident in the top 0-30 cm. The initial planting density had obvious effect on nutrient content in different soil depths. Conclusion] The nutrients in 60 cm soil are affected by stand density in South Asia, while the low initial planting density is more conducive to the long term conservation of soil fertility in Chinese fir plantation.