南亚热带不同人工林对土壤理化性质的影响及土壤质量评价

目的 探讨相同立地条件下的不同人工林对土壤理化性质的影响,为实现人工林养分的精确调控和可持续经营提供科学依据。 方法 选取在柳州沙塘林场马尾松采伐迹地上同为1987年营造的木荷、米老排、蓝果树和杉木人工纯林为研究对象,以未造林灌草地为对照,分层（0～15、15～30、30～50、50～70、70～100 cm）测定14个土壤理化性质指标,结合KMO和Bartlett球形度检验,采用主成分分析法对土壤质量进行综合评价。 结果 同种林分内,随土层加深,土壤密度递增,孔隙度、土壤有机碳、全N、碱解N、有效P含量递减。不同林分间各土壤理化性质差异明显,5种林地的土壤pH值变幅为3.94～5.12;土壤有机碳、全N、碱解N、有效P含量以及化学计量特征C:N、C:P、N:P比值均表现为：阔叶林>针叶林>灌草地;杉木林土壤的全P含量在所有林分中最低,杉木林生长可能消耗更多的磷元素;与对照灌草地相比,营造这4种人工林后使土壤全K含量明显减少,速效K（除米老排林外）也有相似规律,这种变化规律暗示了人工林对K元素的消耗量大;木荷林和杉木林土壤的pH值、全K、速效K及阳离子交换量的含量明显低于其它林分和灌草地。土壤综合质量根据主成分得分依次为：米老排林 >蓝果树林 >木荷林 >灌草地 >杉木林。 结论 （1）人工阔叶林比针叶林能更有效地积累土壤有机碳、N和P等养分,并能明显地优化土壤密度和孔隙度,在今后的造林实践中应优先考虑阔叶林。（2）人工林营造33 a后,土壤全K含量明显地小于对照灌草地,且不同林分间具有差异,因此,在森林经营时应注重K元素调控管理。

Effects of Different Plantations on Soil Physical and Chemical Properties and Soil Quality Evaluation in South Subtropical Zone

Objective To explore the effects of different plantations on soil physical and chemical properties under the same site conditions for providing a scientific basis for the accurate nutrient regulation and sustainable management of plantations. Methods The forests of Schima superba, Mytilaria laosensis, Nyssa sinensis and Cunninghamia lanceolata planted in 1987 on the clearcut sites of Pinus massoniana in Shatang forest farm of Liuzhou were used for analyses, and the non-forested site was used as the control. The 14 soil physical and chemical property indexes were measured in layers (0-15, 15-30, 30-50, 50-70 and 70-100 cm). Combining with KMO and Bartlett’s Test of Sphericit, principal component analysis was used for evaluating soil quality. Results In the same stand, with deepening soil layer, the soil bulk density increased, on the contrast, the contents of porosity, soil organic carbon, total N, alkali hydrolyzable N, and available P decreased. There were significant differences in soil physical and chemical properties among different stands. The soil pH values in the five stands ranged from 3.94 to 5.12. The contents of soil organic carbon, total N, alkali hydrolyzable N, available P, and the stoichiometric characteristics of C:N, C:P and N:P ratios in the broad-leaved forests were the largest, followed by coniferous forests and control stand. The total P content of soil in Cunninghamia lanceolata forest was the lowest. Compared with the control stand, the total K content of soil decreased significantly after planting forests, as well as the available K (except Mytilaria laosensis forest), indicating that the plantations have a large consumption of K element. Moreover, the contents of pH value, total K, available K, and cation exchange capacity of soil in Schima superba forest and Cunninghamia lanceolata forest were significantly lower than those in other forests and control stand. According to the principal component results, the soil quality of Mytilaria laosensis forest were the best, followed by Nyssa sinensis, Schima superba, control stand, and Cunninghamia lanceolata. Conclusion (1) Compared with coniferous forest, broad-leaved forests can accumulate soil organic carbon, N and P more effectively, and can significantly optimize soil bulk density and porosity. Broad-leaved forest should be given priority in afforestation practice in the future. (2) After 33 years of plantation, the total K content of soil is significantly lower than that of the control stand, and there are differences among different forest stands. Therefore, we should pay attention to the regulation and management of K element in forest management.