闽东南沿海2种防护林土壤有机碳和全氮垂直分布1）

摘要

We studied the vertical distribution of soil organic carbon ( SOC) and total nitrogen ( STN) and their relationships with fine root biomass and soil bulk density with 9-year-old plantations of Acacia crassicarpa A.Cunn.ex Benth.and Casu-arina equisetifolia L.on sandy coastal plain soil in southeastern Fujian Province .The fine root biomass of different soil lay-ers was the main factor affecting STN and SOC .Mean contents of SOC and STN across all soil layers were 0.822 g· kg-1 and 0.092 g· kg-1 , respectively, in the A.car ssicarpa forest, while they were 0.934 g· kg-1 and 0.099 g· kg-1 , respec-tively, in the C.equisetifolia forest.SOC and STN contents of the A.crassicarpa and the C.equisetifolia plantations followed the same vertical pattern within the soil profile , and they decreased with soil depth increas , with clear accumulation pat-terns in the surface layer .Soil C/N ratios were 8.93 and 9.42 for A.crassicarpa and C.equisetifolia, respectively, lower than the national average (10-12).SOC and STN storage were 6.908 and 0.777 t· hm-2, respectively, in the A.crassi-carpa forest, while they were 7.840 and 0.838 t· hm-2, respectively, in the C. equisetifoil a plantation and they declined with soil depth increase .SOC and STN contents showed a positive linear relation ( P<0.000 1) , while both of them had a significant negative exponential relationship (P<0.000 1) with soil bulk density.%以闽东南沿海沙地9年生厚荚相思（ Acacia crassicarpa A．Cunn ．ex Benth．）和木麻黄（ Casuarina equi-setifolia L．）林为对象，研究了林地土壤（0～60 cm）有机碳（SOC）和全氮（STN）的垂直分布及其与细根生物量和土壤密度的关系。结果表明：各土层细根生物量是影响STN和SOC主要因素；厚荚相思林地各土层的STN、SOC平均质量分数分别为0．092、0．822 g· kg－1，木麻黄林地各土层的STN、SOC平均质量分数分别为0．099、0．934 g· kg－1；厚荚相思和木麻黄林土壤剖面的SOC和STN质量分数变化规律一致，均随着土层加深而降低，具有明显表聚性特征；厚荚相思、木麻黄林地土壤C／N值分别为8．93、9．42，均低于全国土壤水平（10～12）；各土层SOC和STN储量随土层加深呈下降趋势，厚荚相思和木麻黄林地的SOC储量分别为6．908、7．840 t· hm－2，厚荚相思和木麻黄林地的STN储量分别为0．777、0．838 t· hm－2；SOC和STN呈极显著正线性相关（ P＜0．0001），二者与土壤密度均呈极显著负指数相关（ P＜0．0001）。