不同土地利用方式对赤红壤理化性质的综合影响

通过比较不同土地利用方式下赤红壤pH值、粘粒、容重、孔隙度、有机碳、氮磷钾全量及其速效养分含量的差异，并运用主成分分析方法分析各变量的相互关系、土壤综合理化特征及其关键改良因子。研究结果表明：新垦旱地容重最高，粘粒含量和孔隙度最低；有机碳、全量氮磷钾养分和速效氮磷养分含量均处于较低水平（P<0.05）。果园土容重显著低于其他土地利用方式土壤，且全氮、碱解氮和速效磷钾水平均处于较高水平（P<0.05）。桉树林的全钾和速效钾含量显著高于灌木林，而粘粒含量和速效磷含量相对较低（P<0.05）。主成分分析结果显示：新垦旱地、果园和桉树林、灌木林土壤理化综合质量差异显著（P<0.05），其中新垦旱地当前质量相对较差。有机碳、全氮和速效氮养分缺乏是当前新垦旱地土壤理化质量较差的主要原因。较少的速效磷钾养分含量是当前桉树林地、灌木林土壤质量的限制因素。主成分分析不仅能够区分不同土地利用方式下赤红壤理化质量差异，而且也是探查改良土壤质量因子的有效方法。

Comprehensive Effects of Different Land Uses on Physical and Chemical Properties of Lateritic Red Soil

The study aimed to observe physical and chemical properties of lateritic red soil under different land uses in South China, such as pH, clay contents, bulk density, porosity, organic carbon, total contents of nitrogen, phosphorus, potassium and their available contents. Relationships between these variables, soil quality under different land uses and their main key factors were evaluated by principal component analysis (PCA). Results showed that: the highest bulk density in soil and the lowest clay content and porosity were observed in the newly cultivated dryland; while the lower contents of soil organic C, total N, P, K, available N and P were found as well (P<0.05). The orchard soils have the lowest bulk density in these four kinds of land uses, and higher contents of total N, available N, P and K were showed in our study (P<0.05). Compared to shrub land, the eucalyptus forest soil has higher total and available K contents but lower clay and available P contents, respectively (P<0.05). PCA results showed that significant differences in soil physical and chemical qualities were observed in newly cultivated dry land, orchard land, eucalyptus forest and shrub land (P<0.05), especially the lowest quality were found in newly cultivated dry land. Lower contents of organic C, nitrogen, available N resulted in the lower soil quality of the newly cultivated dry land. In the meantime, lower contents of available P and K limited the improvement of soil quality in eucalyptus forest and shrub land. PCA can not only distinguish physical and chemical properties of lateritic red soil under different land uses, but also can detect their main factors.