中亚热带几种典型森林土壤养分含量分析及综合评价

A comprehensive evaluation of soil nutrients in main typical forests in central-subtropical China

分析及综合评价不同森林植被对土壤养分因子的影响,对揭示森林植被与土壤养分的相互关系,全面衡量森林土壤养分水平具有重要的意义。以中亚热带杉木(Cunninghamia lanceolata)纯林、木荷(Schima superb)纯林、木荷+楠木(Phoebe ahenre)混交林、木荷+杉木混交林、青冈栎(Cyclobalanopsis glauca)天然次生林、毛竹(Phyllostachys edulis)林6种森林类型为研究对象,在分析不同森林类型土壤养分特征状况差异的基础上,采用结构方程模型确定土壤养分因子权重,对其土壤养分水平进行综合评价。结果表明:(1)6种森林类型0—60 cm土壤有机质、全氮、碱解氮和有效磷的含量分别为8.24—28.17 g/kg、0.67—1.31 g/kg、44.88—89.31 mg/kg和1.24—6.50mg/kg,其含量最高的都是青冈栎天然次生林,土壤有机质和碱解氮含量最低的是毛竹林,土壤全氮和有效磷的含量最低的分别为杉木纯林和木荷纯林,0—60 cm土壤全磷和速效钾的含量分别为0.15—0.21 g/kg和35.54—54.32mg/kg,其含量最高的都是木荷+楠木混交林,含量最低的分别为木荷纯林和毛竹林;(2)土壤有机质、全氮、全磷和有效磷的含量在6种森林类型中都一致表现出随土层加深而逐渐减小的规律,而碱解氮和速效钾含量在土壤垂直剖面的变化却因森林类型而异,没呈现出具体的变化规律;(3)栎类天然次生林的土壤养分等级综合评分值为3.47,评价等级属于中上水平,杉木纯林、木荷纯林、木荷+楠木混交林、木荷+杉木混交林的土壤养分等级综合评分值分别为2.45、2.76、2.83、2.68,评价等级均属于中下水平,而毛竹林的土壤养分等级综合评分值仅为1.95,评价等级属于土壤养分缺乏。

Analysis and assessment of the influence of different forest types on soil nutrients are of great significant to reveal the relationships between forests and soil nutrients,and to comprehensively evaluate soil fertility in forests.In this study,characteristics of soil nutrient states were investigated in six forest types(Cunninghamia lanceolata pure forest,Schima superb pure forest,S.superba+Phoebe ahenre mixed forest,S.superba+C.lanceolata mixed forest,Cyclobalanopsis glauca natural secondary forest,and Phyllostachys edulis forest)in central subtropical areas of China,by using the structural equation model.The results showed that:(1)the soil organic matter(SOM),total nitrogen(TN),available nitrogen(AN)and available phosphorus(AP)in soil(0—60 cm)ranged 8.24—28.17 g/kg,0.67—1.31 g/kg,44.88—89.31 mg/kg,and 1.24—6.50 mg/kg,respectively,in the examined forests.The highest values of these nutrients were found in the C.glauca natural secondary forests.The lowest contents of SOM and AN occurred in the P.edulis forests.The lowest contents of soil TN and AP were found in both C.lanceolatapure forests and S.superba pure forests.The contents of total phosphorus(TP)and available potassium(AK)in soil(0—60 cm)ranged 0.15—0.21 g/kgand 35.54—54.32 mg/kg,respectively,in the six forest types,with the highest contents in S.superba+P.ahenre mixed forests,and the lowest contents in S.superb pure forests and P.edulis forests.(2)The SOM,TN,TP and AP contents gradually decreased with increasing of soil depth in the six forest types,but no vertical changing patterns of AN and AK were found in the examined forests.(3)The comprehensive score of soil nutrients was 3.47 in C.glauca natural secondary forests,which belonged to the upper middle level of soil fertility.The comprehensive scores of soil nutrients were 2.45,2.76,2.83 and 2.68 in C.lanceolata pure forests,S.superba pure forests,S.superba+P.ahenre mixed forests,and S.superba+C.lanceolata mixed forests,respectively,which all belonged to the lower middle level of soil fertility.The P.edulis forests had the lowest score of soil nutrients(1.95),indicating that the forest type was in a soil nutrient deficient status in the study region.The results demonstrated that the natural forests are beneficial to maintain soil nutrients and to reduce soil erosion compared to artificial forest plantations.The structural equation model further indicated that the soil organic matter was the most important factor in affecting soil fertility in the six forest types in the studied area.