芦芽山土壤有机碳和全氮沿海拔梯度变化规律

研究不同海拔梯度和坡向的土壤碳氮分布，能在较小的空间尺度上反映不同气候状况下土壤碳氮分布规律，揭示多个互相关联的环境因子对土壤碳氮分布规律的综合影响。对山西省北部芦芽山芦芽山沿海拔梯度土壤有机碳和全氮含量的变化规律进行了分析。自海拔1703.1 m至2756.3 m每上升约50 m设置一个样带（共计21块），每样带内布设30 m＆#215;30 m样地3个，每个样地内“S”形布点，分3层（0~10、10~25、25~40 cm）钻取土样。结果表明，在研究海拔范围内土壤垂直剖面自表层向下有机碳质量分数分别为（35.71±13.32）、（29.18±12.85）和（26.39±12.74） g＆#183; kg-1，全氮质量分数分别为（2.83±0.93）、（2.38±0.84）和（2.12±0.80） g＆#183; kg-1。土壤有机碳和全氮含量的分布特征均表现为随海拔升高而增加的趋势，与海拔呈极显著的线性正相关。土壤有机碳含量与海拔线性模型的回归系数在10~25 cm土层最大，而全氮与海拔线性模型的回归系数随土层深度增加而递减。土壤有机碳含量最高值出现在较高海拔处寒温性针叶林下，而土壤全氮含量最高值出现在最高海拔的亚高山草甸。碳氮含量的剖面分布呈现为表层（0~10 cm）最高，随深度下降而递减。研究区土壤C/N值介于5~19，最小值为海拔最高（2756.3 m）的亚高山草甸，而最大值为较高海拔分布的寒温性针叶林（2332.6 m），沿海拔梯度表现呈“Λ”型的变化趋势。

Distribution characteristics of soil organic carbon and total nitrogen along elevation gradients in Luya Mountain

Better understanding the distribution pattern of soil carbon storage （SOC） and total nitrogen （total N） along elevation gradients will facilitate the projection of global change on terrestrial C and N cycling. Soil organic carbon and total nitrogen contents in 0-0.1, 0.1-0.25 and 0.25-0.4 m soil layers were measured following the standard procedures for four vegetation communities：Subalpine meadow, cold temperate coniferous forest, coniferous and broad-leaved mixed forest and shrub grassland, along elevation gradients from 1 703.1 m to 2 756.3 m on the Luya Mountains in the eastern rim of the Loess Plateau in China. The results showed that the SOC and total N in the three layers were all positive linear correlated with elevation （P＆lt;0.001）. The SOC of different layers are （35.71＆#177;13.32）, （29.18＆#177;12.85） and （26.39＆#177;12.74） g＆#183; kg-1 respectively, and the total N contents are （2.83＆#177;0.93）, （2.38＆#177;0.84） and （2.12＆#177;0.80） g＆#183; kg-1 respectively. Both are decreased with soil depth declined. The CN ratio varied from5 to 19 in study area. The highest value was observed in cold-temperate coniferous forest （2 332.6 m）, but the lowest value in subalpine meadow （2 756.3 m）. The CN ratio variation trend showed “Λ” with elevation gradients and which fitted with the Gaussian model. Elevation induced microclimatic differences and vegetation community types were found to be important factors for the significant variations in SOC and total N in the Luya Mountains.