连栽桉树人工林土壤氮素季节动态特征

Seasonal Dynamic Characteristic of Soil Nitrogen in Eucalyptus Plantations under Successive Rotation

为探讨连栽桉树人工林对土壤氮素的影响,以不同栽植代数(1、2和3代)桉树人工林为研究对象,采用时空替代法,研究连栽桉树人工林土壤氮素(全氮(TN)、铵态氮(NH^+4-N)和硝态氮(NO^-3-N))质量分数的分布及其季节动态特征。结果表明:(1)连栽桉树人工林土壤氮素质量分数在土壤剖面分布的变化规律相一致,其在表层土壤均呈现富集现象,随土层加深而逐渐下降,且NH^+4-N质量分数均高于NO^-3-N质量分数。(2)连栽桉树人工林土壤TN、NH^+4-N和NO^-3-N质量分数均随桉树栽植代数的增加而减少,1~3代桉树林0~20 cm土层的TN、NH^+4-N和NO^-3-N质量分数均低于马尾松人工林;随着土壤深度的增加,不同栽植代数桉树人工林土壤TN、NH^+4-N和NO^-3-N质量分数之间的差异逐渐减少。(3)连栽桉树人工林土壤TN、NH^+4-N和NO^-3-N质量分数均具有明显的季节变化特征,其中TN质量分数由大到小表现为夏季、秋季、春季、冬季,NH^+4-N质量分数由大到小表现为春季、夏季、冬季、秋季,NO^-3-N质量分数由大到小表现为春季、夏季、冬季、秋季。(4)桉树人工林土壤TN、NH^+4-N和NO^-3-N与土壤有机质、速效磷和速效钾存在极显著相关关系(P<0.01),各土壤养分之间也存在一定程度的相关性。

The characteristics of distribution and seasonal dynamics of the soil total N(TN),ammonium-N(NH^+4-N)(AN)and nitrate-N(NO^-3-N)(NN)in different successive rotations of Eucalyptus plantations were investigated by the method of"time by space"to assess the effects of successive planting of Eucalyptus on the content of soil nitrogen.The temporal and spatial variations of soil nitrogen content were examined to elucidate the effect of Eucalyptus plantations of successive rotations on soil nitrogen content.The results indicated that:(1)Soil TN,AN and NN changed consistently along soil profile with decreased trend in deeper soil in Eucalyptus plantations of successive rotations,and AN content was higher compared to NN content.(2)The contents of soil TN,AN and NN in soil decreased with the increment of successive rotations of Eucalyptus,and the contents of TN,AN and NN at depth of 0-20 cm in Pinus massoniana plantations were significantly higher than those in Eucalyptus plantations.With the increasing of soil depth,the differences of soil TN,AN and NN in Eucalyptus plantations of successive rotations gradually decreased.(3)The contents of soil TN,AN and NN exhibited significant seasonal variations in Eucalyptus plantations,including that:TN content in descending order of summer,autumn,spring and winter,AN content in descending order of summer,spring,winter and autumn,and NN content in descending order of spring,winter,autumn and summer,respectively.(4)The correlation analysis showed that soil TN,AN and NN contents in Eucalyptus plantations were extremely significantly correlated to soil organic matter,available-P and available-K(p<0.01),and there was certain correlations between soil TN,AN and NN contents and other nutrients.