OC,TN And TP Content And Their Stoichiometric Characteristics In Tree Leaves,Litter And Soil Of Four Typical Plantation Tree Species In The Alpine Zone Of The Loess Plateau In Qinghai

The aim of this study was to explore the relationship of the organic carbon(OC),total nitrogen(TN),total phosphorus(TP)content and their stoichiometric characteristics in leaves,litter and soil of four typical plantation trees(Larix principis-rupprechtii、Picea crassifolia、Betula platyphylla、Populus cathayana)in the alpine zone of the Loess Plateau in Qinghai change with the coniferous and broad-leaved tree species,the months of the growing season and the slope positions,and to figure out the nutrient storage status,diffferences and circulation mechanism of each part of the local plantation ecosystem,and provide a theoretical basis for guiding its healtheir operation and management.In this paper,the method that combined field manual sampling with indoor experimental analysis was used to obtain the OC,TN,TP content data of the leaves,litter and soil samples.And the nutrient content characteristics and stoichiometric characteristics of leaves were analyzed by Shapiro-Wilk normality test,single factor analysis of variance,Duncan post-mortem multiple test,spearman correlation analysis and RDA analysis.The results showed that:(1)The mean values of OC,TN,and TP content in the leaves of the four typical pure plantations in the alpine zone of the Loess Plateau in Qinghai were 591.84,17.76 and 1.47 g/kg,and the variability was TP> TN> OC.The mean values of C:N,C:P,and N:P were 38.87,1042.97,28.32,and the variability was C:P>N:P>C:N.Except for Picea crassifolia,the TN and TP content in leaves of the other three tree species showed a very significant positive correlation.The mean values of C:N and C:P in leaves of Picea crassifolia were at a high level,while N:P was at a low level,indicating that the growth rate of Picea crassifolia was relatively slow and its growth was more limited by TN.Months of the growing season and coniferous and broad-leaved tree species were two important factors affecting leaves nutrient content and stoichiometric ratios of four typical plantation trees in the alpine zone of the Loess Plateau in Qinghai.The leaves TN content of the broad-leaved trees was higher than that of the coniferous trees.The leaves TN content and TP content,C:N and C:P of the broad-leaved trees were affected by the months of the growing season more than that of the coniferous trees.Because of interference from human activities,trees grow relatively slowly in the downhill position.(2)The mean values of OC,TN,and TP content in the litter of the four typical pure plantations in the alpine zone of the Loess Plateau in Qinghai were 396.89,14.55 and 6.23g/kg.The mean values of C:N,C:P,and N:P were 34.18、172.26、5.21.Litter C:P and N:P showed significant or extremely significant positive correlation.Months of the growing season,coniferous and broad-leaved tree species were two important factors affecting litter nutrient content and stoichiometric ratios of four typical plantation trees in the alpine zone of the Loess Plateau in Qinghai.The litter TN content of the broad-leaved trees was higher than that of the coniferous trees,the litter C:N of the coniferous trees was higher than that of the broad-leaved trees.The leaves TN content of the broad-leaved trees was higher than that of the coniferous trees.The litter TP content and N:P of the coniferous trees were affected by the months of the growing season more than that of the broad-leaved trees.The litter C:N of the broad-leaved trees was more affected by slope position than coniferous trees.(3)The mean values of OC,TN,and TP content in the surface soil(0-10cm)of the four typical pure plantations in the alpine zone of the Loess Plateau in Qinghai were 23.20,1.13 and 0.28 g/kg,the mean values of C:N,C:P and N:P were 23.89,221.02 and 9.25.Soil TN content and N:P showed significant or highly significant positive correlation,C:N and N:P showed significant or highly significant negative correlation.Coniferous and broad-leaved tree species were important factors affecting nutrient content and stoichiometric ratios of surface soil(0-10cm)of four typical plantation trees in the alpine zone of the Loess Plateau in Qinghai.The content of TN and C:P,N:P of the surface soil(0-10cm)under the broad-leaved trees were higher than those of the coniferous trees.In the0-60 cm depth soil,the content of OC and TN,C:P and N:P decreased with the soil layers deepened.The coefficients of variation of soil OC,TN,TP content,C:N,C:P and N:P under the broad-leaved trees in different soil layers of 0-60 cm were all larger than coniferous trees.(4)For the coniferous trees in the alpine zone of the Loess Plateau in Qinghai,the correlation between nutrients in leaves,litter and soil was more obvious,but for the broad-leaved trees,the correlation between nutrients was obvious only between litter and soil.The TP content in litter,leaves and surface soil decreased in turn,while the OC and TN content in leaves,litter,and surface soil decreased in turn.