不同坡位轻木人工林土壤养分含量及其化学计量特征OA北大核心CSTPCD

Carbon(C),nitrogen(N)and phosphorus(P)are commonly used to assess soil quality.To understand the differences in soil C,N and P contents and their stoichiometric characteristics under Ochroma pyramidale grown in different slope positions in Xishuangbanna region,this study took biennial plantations of O.pyramidale as subjects,the stoichiometric characteristics of soil C,N and P and their effects on growth of O.pyramidale were analyzed and compared between upper and lower slopes based on field sampling and inves-tigation and laboratory analysis.The contents of soil organic carbon(SOC),total nitrogen(TN),total phos-phorus(TP),alkaline nitrogen(AN)and available phosphorus(AP)were determined,and the differences in the ratios of SOC/TN,SOC/TP,TN/TP and AN/AP between the two slopes were assessed.The results were as follows.①Compared with the lower slope position,the tree height and diameter at breast height of O.pyramidale at the upper slope position increased by 23.39%and 49.43%,respectively.② Decreasing tends were found in contents of soil SOC,TN,TP,AN and AP with increasing of soil depth,among which,AP content in all the three soil layers and AN content in 20～40-cm soil layer were significantly higher in the lower slope position than that in the upper slope position.③All the soil nutrient contents except for TP in the upper slope position in 40～60-cm soil layer were significantly lower than those in 0～20-cm layer;the AN/AP ratio in all the three soil layers was significantly higher in the upper slope position compared with the lower slope position;the SOC/TP ratio in the 20～40-cm and 40～60-cm soil layers were significantly higher in the lower slope position than that of the upper slope position.④Through correlation and principal component analyses,the soil fertility in the upper slope position was mainly reflected by the SOC/TP,AN/AP and SOC/TN ratios,and the soil nutrient situation in the lower slope position was mainly reflected by the AP,AN and SOC con-tents.In summary,the growth of O.pyramidale in the lower slope position was significantly better than that in the upper slope position,and the soil SOC,AP and AN contents played key roles,which also reflected the conversion of TP and TN to AP and AN.The AN/AP ratio reflected the nutrient availabe efficiency in soil,which had direct correlation to the growth of O.pyramidale,so it could be used as a signal for local assessment of nutrient deficiency in the woodland.