泥石流频发区山地不同海拔土壤化学计量特征——以云南省小江流域为例

Soil stoichiometry characteristics at different elevation gradients of a mountain in an area with high frequency debris flow: a case study in Xiaojiang Watershed,Yunnan

为了探究泥石流频发区不同海拔梯度土壤的化学计量特征,阐明土壤性质对海拔变化的响应规律,进而有效指导受限性生态脆弱区生态系统的保护和恢复,在云南省小江流域支流阿旺小河西北侧山地选取了1500—2000m、2000—2500m、2500—3000m 3个海拔梯度,测定各海拔梯度范围内0—10cm、10—20cm、20—30cm土壤的有机碳、全氮、全磷、全钾含量及其机械组成,分析了不同海拔梯度土壤化学计量比的垂直分布特征及其与植被区、土壤物理结构的关系。结果表明:随着海拔梯度的升高,土壤有机碳和全氮含量以及碳磷比、碳钾比、氮磷比和氮钾比均呈升高趋势,全磷和全钾含量以及磷钾比呈降低趋势,且有机碳、全氮、全磷和全钾对海拔的敏感程度依次降低;不同海拔梯度之间,土壤有机碳、全氮、全磷、全钾及其化学计量比的垂直分布存在显著差异性,即随着土壤深度的增加,有机碳和全氮含量呈降低趋势,而全磷和全钾含量以及各化学计量比变化规律不明显;同一海拔梯度内,森林植被区和灌草丛群落植被区土壤生态化学计量比差异性不大,且随海拔梯度变化一致,灌草丛群落中,土壤碳氮比与地上植被盖度具有极显著正相关性,森林群落植被区,土壤磷钾比与优势乔木种平均高度具有极显著负相关性,而与平均胸径呈显著负相关性;土壤物理结构的分异是造成土壤化学计量特征发生变化的主要内在原因,土壤碳磷比、碳钾比、氮磷比、氮钾比随着含水率和砂粒的增加呈指数型上升而随着粘粒的增加呈指数型下降的趋势。

To understand soil stoichiometric characteristics at different elevations in a mountainous area with high frequency debris flows, organic carbon （ SOC）, total nitrogen （ TN）, total phosphorus （ TP）, total potassium （ TK）, and mechanical characteristics of soil from 3 elevational bands （ 1500--2000, 2000--2500, 2500--3000 m） were measured at different soil depths. This study also analyzed vertical variations in soil stoichiometric characteristics in these elevational gradients and its correlation with soil physical structure. SOC, TN, C ：P, C ：K, N ：P, and N ：K were positively correlated with elevation, while TP, TK, and P ：K were negatively correlated with elevation. SOC had the strongest relationship with elevation, followed by total N, P, and K. The vertical distribution of SOC, TN, TP, TK, and stoichiometric ratio varied with elevation.SOC and TN decreased with soll depth, but there was no clear relationship with TP, TK, or stoichiometric ratio. Within each elevational band, soil stoichiometric characteristics did not differ significantly between forest communities and shrub-meadow communities; both presented the same pattern as the elevation changed. In the shrub-meadow community, C ：N was significantly correlated with above ground vegetation cover. In the forest community, P ：K was significantly correlated with mean tree height. Differences in soil physical structure were the key factor linked to c characteristics. C：P, C ：K, N ：P, and N ：K had a positive exponential relationship with content, and a negative exponential relationship with clay content. hanges in soil stoichiometric soil water content and sand