采用时空互代法,探讨不同林龄对桂北低山丘陵地区桉树林土壤SOC,TN,TP和TK养分变化及其生态化学计量学特征的影响。结果表明:1)随林龄的增加,SOC表现为先升高后降低再增加的趋势,TN无明显变化规律,TP趋于减少,TK表现为先减小后增大的趋势。不同林龄SOC,TN,TP和TK含量均随土层深度的增加而减少。2)随林龄的增加,土壤C:N,C:P,N:P和C:K表现为逐渐增大的趋势,N:K表现为先增大后减小的趋势,P:K无明显规律。随土层的加深,土壤C:N逐渐增大,N:P,N:K逐渐减小。C:P,C:K和P:K无明显变化规律。3)SOC与C:P,N:P,N:K呈极显著正相关,TN与N:P,N:K呈极显著正相关。TP与N:K呈极显著正相关,TK与N:P呈极显著正相关。不同林龄、土层深度均影响土壤养分的分配,土壤养分对桉树林土壤化学计量的贡献表现出一定的差异性。

By using the space-time intergenerational method,the Eucalyptus plantations of different ages of plantation in low hilly areas at Guangxi were taken as the research object.The effects of forest age on soil organic carbon(SOC),total nitrogen(TN),total phosphorus(TP) and total potassium(TK) and their ecological stoichiometric characteristics of soils were studied.The results showed that:1)With the increase of Eucalyptus forest age,SOC showed a trend of increasing first,then decreasing and increasing again.TN had not evident regular change.It showed that the trend of decreasing first and then increasing later for TK.SOC,TN,TP and TK concent in the five different plantations decreased significantly with the increase of soil depth.2) The C:N,C:P,N:P and C:K ratios of soil increased significantly with the growth of forest age.The N:K ratios increased first and then decreased.There are no obvious regular patterns for P:K ratios of soil.The C:N ratios increased with the increase of soil depth,the N:P and N:K ratios decreased on the contrary,but C:P,C:K and P:K ratios showed no consistent pattern.3) It showed that significant positive correlation was found between SOC content and C:P ratios,N:P ratios and N/K ratios;among TN content,N:P ratios and N:K ratios;between TP content and N:K ratios and between TK content and N:P ratios.Different forest ages and soil depths all affected the distribution and utilization of soil nutrients.In general,the ecological stoichiometric ratios of soils from surface are higher than those of sub-layer soil.It will provide the scientific basis for the restoration of the forest ecosystem in Guangxi Province.