不同林分土壤磷形态与磷酸酶特征

Characteristics of soil phosphorus fractions and phosphatases activity in different plantations

以湖南省平江县国有芦头林场的次生林以及经人工翻垦种植的油茶(Camellia oleifera)、黄桃(Amygdalus persica)、杨梅(Myrica rubra)和杉木(Cunninghamia lanceolata)四种人工林为研究对象,比较了不同林分土壤理化性质、磷酸酶活性与磷形态特征,分析了三者之间的相关性,探讨了次生林转变为人工林后,土壤磷形态和磷酸酶的变化特征以及驱动土壤磷素形态变化的关键因子。结果表明:(1)次生林土壤有机碳(SOC),全氮(TN)、铵态氮(NH^(+)_(4)-N)含量与磷酸酶活性显著高于其他四种林分。(2)五种林分中土壤残余磷(Residual-P)含量最高,是林地土壤主要的磷素存在形态。林分转变后,黄桃林与杉木林树脂提取态无机磷(Resin-Pi)显著增加,黄桃林与油茶林NaHCO_(3)提取态磷(NaHCO_(3)-Pi、NaHCO_(3)-Po)含量显著增加,而四种人工林的NaOH提取态有机磷(NaOH-Po)含量均显著降低。可利用磷、中等可利用磷与稳定态磷含量及其占全磷的比例在五种林分中差异显著,其中黄桃林与油茶林可利用磷占全磷比例较高;杨梅林和杉木林中等可利用磷占总磷比例较高;油茶林与次生林中稳定态磷所占全磷比例较高。(3)相关分析表明土壤中可利用磷与全钾(TK)呈显著正相关,中等可利用磷与硝态氮(NH^(-)_(3)-N)呈显著正相关,稳定态磷与SOC、TN、NH^(+)_(4)-N均呈显著正相关,磷酸酶活性与SOC、TN、NH^(+)_(4)-N显著正相关。综上所述,次生林转变为人工林不仅改变了土壤中总磷的含量,而且影响了不同磷形态之间的转化,导致土壤中磷的赋存状况发生改变。

In order to clarify the differences in soil phosphorus forms and phosphatase activities in different forest types,we investigated the characteristics of soil properties,phosphorus(P)fractions,and phosphatase activities in a secondary forest and four artificial plantations(Camellia oleifera,Amygdalus persica,Myrica rubra and Cunninghamia lanceolata)in Lutou National Station for Scientific Observation and Research of Forest Ecosystems,Hunan Province.Correlations among soil properties,phosphorus fractions and phosphatase activities were analyzed,and the influencing factors driving the differences in soil phosphorus forms and phosphatase activities were identified.The results showed that:(1)the contents of soil organic carbon(SOC),total nitrogen(TN),ammonium nitrogen(NH^(+)_(4)-N)and the activities of phosphatase in the secondary forest were higher than in the four plantations.(2)the content of residual-P was the highest in the five forest types,and residual-P was the dominant phosphorus form in forest soils.After forest conversion,resin extractable inorganic P(Resin-Pi)increased significantly in Amygdalus persica and Cunninghamia lanceolata plantations.The contents of NaHCO_(3)extractable P(NaHCO_(3)-Pi,NaHCO_(3)-Po)increased significantly in Amygdalus persica and Camellia oleifera plantations,whereas the content of NaOH extracted organic P(NaOH-Po)decreased significantly in all plantations.The contents and proportions of easily-available P,moderately-available P and non-available P in soils differed significantly among the five forest types.The proportion of easily-available P in total P was higher in Amygdalus persica and Camellia oleifera plantations than in other forests,while a higher proportion of moderately-available P in total P was found in Myrica rubra plantations and Cunninghamia lanceolata plantations.The proportion of non-available P in total P was higher in Camellia oleifera and the secondary forest compared with other forests.(3)correlation analysis demonstrated that easily-available P was positively correlated with total potassium(TK),moderately-available P was positively correlated with nitrate nitrogen(NH^(-)_(3)-N),non-available P was positively correlated with SOC,TN,NH^(+)_(4)-N,and phosphatase activity was positively correlated with SOC,TN,NH^(+)_(4)-N.In conclusion,the conversion of secondary forest to plantations not only changed the soil total P contents,but also affected the transformation of phosphorus forms,resulted in the differences of the occurrence of P in soil.