红壤侵蚀区崩岗土壤养分化学计量特征分异规律

Variation of Stoichiometric Characteristics of Soil Nutrients in Collapse Mound of Eroded Red Soil Region

以福建省西南部长汀县濯田镇黄泥坑崩岗群内植被盖度分别为2%,20%和95%的3处相邻崩岗为研究对象,对各崩岗内集水坡面、崩壁(顶部、中部及底部)、崩积体(上部和下部)和沟道出口7个典型部位0—10,10—20,20—30cm土壤基本理化性质进行测定,分析了各植被盖度崩岗不同深度及部位土壤化学计量比的空间分异规律。结果表明:随着植被盖度的升高,土壤养分含量及化学计量比显著增加(除全磷含量和P/K以外);随着土壤深度的增加,有机碳、全氮和全钾含量以及C/N、C/P、C/K和N/P总体上呈减少趋势,全磷含量以及N/K和P/K基本维持稳定;沿集水坡面→崩壁→崩积体→沟道出口,有机碳、全氮和全钾含量以及C/N、C/P、C/K、N/P和N/K基本表现为先减少再增加最后亦降低的变化趋势,全磷含量和N/P无明显差异;土壤化学计量特征与土壤养分含量、粉粒含量、容重、含水量和pH具有较强的相关关系。崩岗系统土壤物理结构较差,养分含量普遍较低,其中有机碳、全氮和全磷含量存在不同程度的限制。

3adjacent typical collapse mounds（Ⅰ,Ⅱ and Ⅲ）were selected in Huangniken collapse mound group in Zhuotian Town,Changting County of southwestern Fujian Province,in which vegetation coverage of each collapse mound was 2%,20%and 95%,respectively;seven plots including upper catchment,collapsing wall（top,middle and bottom part）,colluvial deposit（upper and lower part）and channel outlet for each collapse mound were sampled,and the main physical and chemical properties including particle composition,bulk density,water content,pH value,soil organic carbon（SOC）,total nitrogen（TN）,total phosphorus（TP）and total potassium（TK）in 3depths（0—10cm,10—20cm and 20—30cm）of each plot were measured.Meanwhile,spatial variation of the contents of SOC,TN,TP,TK and their stoichiometric characteristics in each collapse mound with different depth and position were analyzed in this paper.The results indicated that with improvement of vegetation coverage（fromⅠto Ⅲ）,the contents of SOC,TN,TP,TK and their stoichiometric ratios increased significantly with the exception of TP content and P/K,and the order of increasing range of soil nutrients was SOC〉TN〉TK〉TP,while that of soil stoichiometric ratios was C/P〉C/K〉C/N〉N/K〉N/P〉P/K.Under different depth（from 0—10cm to 20—30cm）,the contents of SOC,TN,TK and the ratios of C/N,C/P,C/K and N/P generally decreased,while the content of TP and the ratios of N/K and P/K basically remained stable.Variation of soil nutrient contents and their stoichiometric ratios for different position were greatly obvious in each collapsing hill：the contents of SOC,TN,TK,C/Nand C/P,C/K,N/P and N/K showed a down-up-down variation tendency along the runoff routes from upper catchment to channel outlet via collapsing wall and colluvial deposit,while TP content and P/K ratio kept relatively consistent.Besides,soil stoichiometry was closely related to nutrient content,silt content,bulk density,water content and pH value by stepwise regression analysis.In summary,the contents of C,N and P were at very low level,especially P content in the severely eroded context of collapse mound.