不同栽植代数杉木人工林土壤磷素特征研究

Characteristics of Soil Phosphorus in Cunninghamia lanceolata Plantations with Different Planting Rotations

[目的]研究不同栽植代数杉木林土壤磷素变化规律和形态特征,确定影响杉木林土壤磷素有效性的因素,为提高连栽杉木对磷素的利用效率和我国杉木林的可持续经营提供理论依据。[方法]对土壤全磷、有效磷、不同形态无机磷含量进行测定,利用31P核磁共振技术(31P-NMR)和扫描电镜-X-射线能谱(SEMEDS)、傅里叶红外光谱(FTIR)、X射线衍射(XRD)技术对土壤磷素形态特征和土壤结构及矿物组成进行分析。[结果]31P-NMR图谱表明:连栽导致杉木林土壤正磷酸盐含量下降,正磷酸单酯含量增加。土壤全磷(TP)、有效磷(AP)、磷酸钙盐(Ca-P)含量随杉木林栽植代数的增加而减少,闭蓄态磷(O-P)含量则相反;O-P含量在各形态无机磷中占比最大,磷酸铝盐(Al-P)含量占比最小。SEM-EDS分析发现:不同栽植代数杉木林土壤胶体颗粒呈片状堆叠;FTIR图谱显示:其表面官能团结构的差异较小;XRD分析表明:高岭石和石英的衍射峰强度随栽植代数的增加而减弱。[结论]不同栽植代数杉木林土壤形态主要以正磷酸盐和正磷酸单酯为主。连栽土壤中全磷、有效磷、磷酸铝盐、磷酸铁盐(Fe-P)向土壤表层聚集分布,土壤中正磷酸盐(无机磷)含量随杉木林栽植代数的增加而减少,土壤Al-P含量较少及有效磷、Ca-P、Fe-P向极难溶的OP转化是导致连栽杉木林土壤有效磷含量低的重要因素。连栽可增大土壤熟化程度、降低土壤矿物质结晶程度。

[Objective]To study the changes of soil phosphorus and morphological characteristics in Cunninghamia lanceolata plantations with different planting rotations and to determine the factors affecting soil phosphorus availability of C.lanceolata plantation.[Method]The contents of total P,available P and inorganic P in the soil were determined,and the characteristics of phosphorus form,structure and mineral composition in soil were analyzed by using 31P-NMR,SEM-EDS,FTIR and XRD.[Result]The results of 31P-NMR analysis showed that the content of orthophosphate decreased,and the content of orthophosphoric monoester increased in C.lanceolata plantation after successive planting.The contents of total P,available P and Ca-P in soil decreased with the increase of planting rotations,which was opposite in the contents of O-P.The O-P content took the largest proportion among all forms of inorganic phosphorus,while the Al-P content took the smallest proportion.The SEM-EDS analysis showed that the soil colloid particles were stacked in sheets.The FTIR spectra showed that there was little difference in the surface functional group structure.The XRD analysis showed that the diffraction peak intensity of kaolinite and quartz decreased with the increase of planting rotation.[Conclusion]The soil morphology of C.lanceolata plantations with different planting rotations is mainly dominated by orthophosphate and orthophosphoric monoester.The total P,available P,Al-P and Fe-P will accumulate and distribute to the soil surface layer with the successive planting.The content of orthophosphate in the soil will decrease with the increase of planting rotations.Less content of Al-P in soil and the conversion of available P,Ca-P,Fe-P to the extremely insoluble O-P are important factor leading to low content of available phosphorus in the soil of successive planted C.lanceolata plantation.Successive plantation will increase the degree of soil maturation and decrease the degree of soil mineral crystallization.