Ecological stoichiometry characteristics of soils from main plantations in karst plateau mountainous area

ObjectiveThis study aimed to explore contents of carbon(C),nitrogen(N),phosphorus(P)and potassium (K)as well as ecological stoichiometry characteristics in soils from major plantations in karst plateau mountainous areas in order to provide reference for investigating soil nutrients limitation,vegetation restoration and ecosystem reconstruc-tion.MethodRosa roxburghii plantation,Juglans regia plantation and bare land in Salaxi demonstration region,Bijie were sampled in field. Soil chemical properties from the three plantations at different soil depths were compared by indoor analysis.ResultContents of soil organic carbons(SOC),total nitrogen(TN),available nitrogen(AvN),total phospho-rus(TP)and available phosphorus(AvP)decreased as a whole as soil depths increased. Total potassium(TK)content and available potassium(AvK)content changed among various soil depths,but the variations were insignificant(P>0.05). Overall,the nutrients accumulated in surface layers. Soil C/N,C/P,C/K,N/P,N/K and P/K ratios presented some differen-ces. C/N ratios of soil at different depths were the highest in R. roxburghii. The rank of C/P ratios in soils was R. rox-burghii>bare land>J. regia. C/K ratios decreased with the increase of soil depth. The performances of N/K and P/K ratio were J. regia>bare land>R. roxburghii. Variation coefficients of soil ecological stoichiometry characteristics for R. rox-burghii,J. regia and bare land were 11.14%-31.25%,5.59%-17.14%and 6.82%-23.71%respectively. Correlation analy-sis showed that significant positive correlation was found between SOC content and TN content,TP content,C/K ratio and N/K ratio;between TN content and TP content,C/K ratio and N/K ratio;between TP content and C/K ratio,N/K ra-tio;between TK content and N/P ratio and between C/K ratio and N/K ratio(P<0.01,the same below). However,there was extremely significant negative correlation between TN content and TK content,C/N ratio;between TP content and TK content,C/N ratio and N/P ratio;between TK content and C/K ratio,N/K ratio and between C/N ratio and N/K ratio.ConclusionSoil nutrient distributions in different plantation sample plots are all affected by soil depth,the nutrients are mainly accumulated in surface layers with low N and P concentrations in these soils. In general,the ecological stoichio-metric ratios of soils from surface are higher than those from sub-layer soil,and soil contributions to it is different.