闽北3种人工林土壤游离氨基酸组成及其差异研究
Composition of Soil Free Amino Acid and Its Difference in Three Plantations in Southern China

3种人工林土壤游离氨基酸总含量表现出明显的垂直分布特征.针阔叶混交林和针叶林表层(0～20 cm)土壤游离氨基酸含量显著高于深层(20～40 cm)土壤的含量(P＜0.05)；而阔叶林表层土壤游离氨基酸含量低于深层土壤的含量,但差异不显著.土壤游离氨基酸各组分均表现出显著的垂直分布特征,阔叶林表层土壤中天冬氨酸、谷氨酸、组氨酸、精氨酸和苯丙氨酸的含量显著高于深层土壤对应组分的含量,但苏氨酸、脯氨酸、甘氨酸、丙氨酸、亮氨酸显著低于深层土壤对应组分的含量；针阔叶混交林表层土 壤中酪氨酸、组氨酸和脯氨酸低于深层土壤的含量,而其余组分均显著高于深层土壤的含量；而针叶林中除甲硫氨酸和赖氨酸外,其余15种氨基酸在表层土壤中的含量均高于深层土壤中对应组分的含量.3种人工林中无论是表层土壤还是深层土壤,游离氨基酸均以中性氨基酸含量为最高,碱性和酸性氨基酸含量次之,含硫氨基酸含量最低.表层土壤中天冬氨酸、丝氨酸、谷氨酸、甘氨酸、丙氨酸、缬草氨酸、甲硫氨酸、异亮氨酸、亮氨酸和精氨酸的含量依次为:针叶林＜阔叶林＜针阔叶混交林,而赖氨酸和脯氨酸的含量则以针叶林为最高,针阔叶混交林次之,阔叶林最低；阔叶林表层土壤中络氨酸和胱氨酸含量最高.深层土壤中各组分氨基酸除赖氨酸之外均以针叶林中含量最低,针阔叶混交林次之,而阔叶林中含量最高.
The total contents of soil free amino acids total nitrogen in the three plantations showed significant vertical distribution characteristics.Free amino acid contents in 0～20 cm layer soil were significantly higher than that in 20～40 cm layer soil in the leaved-mixed and coniferous forest(P<0.05).However,the total contents of free amino acid in 0～20 cm layer soil less than in 20～40 cm layer soil in the broad-leaved forest.Moreover,contents of every component of free amino acids in soil also showed significant vertical distribution characteristics.Contents of aspartic acid,glutamic acid,histidine,arginine and phenylalanine in topsoil were respectively higher than in deep soil in the broad-leaved forest topsoil,but content of threonine,proline,glycine,alanine and leucine were respectively lower than in deep soil.Content of tyrosine and histidine and proline in topsoil were respectively lower than that in deep soil in the borad-leaved mixed plantation,while the rest components of free amino acids in topsoil were significantly higher in deep soil.Contents of every composition of the free amino acids except for methionine and lysine in topsoil were respectively higher than in the deep soil in coniferous forest.Neutral amino acid content either in topsoil or in deep soil in the three plantations was highest in the four amino acids,followed by alkaline and acidic amino acid content,and sulfur-containing amino acids content was lowest.Contents of aspartic acid,serine,glutamic acid,glycine,alanine,valerian leucine,methionine,isoleucine,leucine and arginine in topsoil were highest in mixed broadleaf forest followed with that in broad-leaved forest and lowest in coniferous forest.However,lysine and proline content in topsil were just the opposite.And the contents of every component of amino acids except lysine in the deep soil were highest in broad-leaved forest,followed in mixed broadleaf forest,and lowest in coniferous forest