马尾松纯林改造成针阔混交林后土壤化学性质的变化

在25 a生的马尾松林下分别套种火力楠、闽粤栲、苦槠、格氏栲、青栲和拉氏栲等阔叶树种的1 a生幼苗,16年后形成郁闭的针阔混交异龄林。土壤化学分析结果显示,在马尾松林下套种阔叶树(除青栲外)明显增加了林下表层土壤(0~20 cm)的有机质含量。各林分下土壤全K、全M g、全C a、全N和全P的平均含量分别为11.41,6.64,4.33,1.45,0.46 g/kg,表明土壤K、M g、C a的含量比较丰富,而N和P则相对缺乏,营造混交林在一定程度上增加了土壤N、P含量。所有混交林深层土壤(20~60 cm)的有效N、P含量均大于马尾松纯林,而有效K的含量则相反。混交林下0~20 cm,20~40 cm和40~60 cm土壤的平均pH值分别为4.40,4.61和4.68,而马尾松纯林下各土层的pH值则依次为4.39,4.41及4.42,说明在马尾松林下套种阔叶树在一定程度上降低了20 cm以下土层的活性酸度。套种阔叶树(除苦槠外)后由于降低了土壤交换性酸度,增加了土壤盐基离子浓度,从而明显提高了土壤盐基饱和度。

Changes of Soil Chemical Properties after Pure Massons Pine PlantationsTransferred into Mixed Conifer-Hardwood Stands

One-year old seedlings of six broad-leaved tree species,Michelia macclurei,Castanopsis fissa,Castanopsis sclerophylla,Castanopsis kawakamii,Cyclobalanopsis myrsinaefolia and Castanopsis lamontii,were separately planted under 25-year-old Masson's pine plantation,and developed into different closed mixed forests after 16 years.The major chemical properties of the soils supporting the six mixed stands and the pure Masson's pine plantation were analyzed to study the response of the soils to the interplanting practice.The results showed that planting broad-leaved species(excluding Cyclobalanopsis myrsinaefolia) under Masson's pine stand significantly increased organic matter contents in the surface soils(0~20 cm).The average contents of total K,Mg,Ca, N and P in the soils beneath all the seven types of stands(including pure Masson's pine stand) were 11.41,6.64,4.33,1.45,and 0.46 g/kg,respectively,suggesting the soils holding abundant K,Mg and Ca,but lacking N and P.Establishment of mixed forests,to some extents,improved the status of N and P supplies in the soils.The contents of available N and P featuring the mixed stands were consistently greater than the single-species plantation,but reverse for available K.The average pH value of the soils under the mixed stands was 4.40 in the depth of 0~20 cm,4.61 in 20~40 cm,and 4.68 in 40~60 cm,but the pH values in the corresponding soil layers under pure stand were 4.39,4.41 and 4.42, respectively,indicating interplanting broad-leaved species decreased the acidity of the soil solutions.The practice of growing broad-leaved species(except Castanopsis sclerophylla) under Masson's pine canopy elevated percent base saturation of the soils,due to the interactive effects of decreased exchange acidity and increased basic cation concentrations.