木麻黄纯林及其混交林对土壤剖面理化性质的影响

为明确混交林对木麻黄林地土壤肥力的改善作用,该文选取海南岛北部滨海沙地木麻黄纯林、木麻黄-琼崖海棠混交林、木麻黄-大叶相思混交林3种林分类型,通过采集土壤剖面样品,分析腐殖质层、0～100 cm土壤各层次的理化性质、分布特征及其林分间差异。结果表明:(1)与纯林相比,木麻黄-琼崖海棠混交林可显著提高腐殖质层以及20～40 cm土壤层pH,增幅分别为6.11%和5.97%。(2)与纯林相比,木麻黄-琼崖海棠混交林和木麻黄-大叶相思混交林均可显著提高各层土壤的有机碳和全氮含量,有机碳含量增幅分别为69.8%～358.3%和90.2%～908.3%,全氮含量增幅分别为44.1%～160.7%和31.4%～210.7%; 另外,木麻黄-琼崖海棠混交林还可显著提高0～100 cm各土层的全磷含量,增幅为20.8%～39.6%,而木麻黄-大叶相思混交林可显著提高20～100 cm各土层的全磷含量,增幅为25.0%～39.6%; 木麻黄-大叶相思混交林对腐殖质层速效养分的改善效果较好,而两种混交林均可显著提高各土层的速效钾含量。(3)方差分析表明,林分类型和土层深度对林下有机碳、全氮、全磷、有效磷、硝态氮和铵态氮含量均有极显著的交互作用影响。综上结果认为,木麻黄混交林对林下土壤肥力具有明显的改善作用。建议在构建木麻黄防风林时应重点考虑混交林模式,尤其是与大叶相思混交林的种植模式来更好地提升土壤肥力,以保障可持续生产。

Effects of pure and mixed plantations of Casuarina equisetifolia onsoil profile physico-chemical properties

In order to clarify the improvement effect of mixed plantations on soil fertility of Casuarina equisetifolia plantations, three forest plantations were selected, i.e. pure plantation of Casuarina equisetifolia, mixed plantation with Casuarina equisetifolia and Calophyllum inophyllum, mixed plantation with Casuarina equisetifolia and Acacia auriculiformis in coastal sandy land at Northern Hainan Island. By collecting soil profile samples from different plantations, the distribution characteristics of soil physico-chemical properties and their differences among plantations were discussed. The results were as follows:(1)Compared with the pure plantation of Casuarina equisetifolia, the mixed plantation with Casuarina equisetifolia and Calophyllum inophyllum significantly increased pH by 6.11% and 5.97% at the humus horizon and 20-40 cm soil depth, respectively.(2)Compared with the pure plantation of Casuarina equisetifolia, the contents of soil organic carbon(SOC)was increased by 69.8%-358.3% and 90.2%-908.3%, and the contents of soil total nitrogen(TN)was increased by 44.1%-160.7% and 31.4%-210.7% in different soil depths of two mixed plantations, respectively; The contents of soil total phosphorus(TP)increased by 20.8%-39.6% in different soil depths from 0-100 cm in mixed plantation with Casuarina equisetifolia and Calophyllum inophyllum, and increased by 25.0%-39.6% of 20-100 cm soil depth of mixed plantation with Casuarina equisetifolia and Acacia auriculiformis; The mixed plantation with Casuarina equisetifolia and Acacia auriculiformis showed the better improving effect on available nutrients in humus horizon than the other plantations, while both mixed plantations could significantly increase the available potassium contents in different soil depths.(3)Variance analysis showed that plantation type and soil depth had significantly interactive effects on the contents of SOC, TN, TP, available phosphorus(AP), nitrate nitrogen(NO₃^--N)and ammonium nitrogen(NH₄⁺-N). In conclusion, the mixed Casuarina equisetifolia plantations can significantly improve the soil fertility. Hence, in order to ensure the sustainable production, more attention should be paid to the mixed plantation structures, especially with Acacia auriculiformis, to get better fertility.