The Characteristics Of Soil And Litter Organic Carbon And Total Nitrogen In Different Age Groups Of Quercus Aliena Var. Acuteserrata And Pinus Armandii Forests In The Qinling Mountains

Carbon and nitrogen are extremely important chemical elements in forest ecosystems.They can limit biological growth and material cycling in terrestrial ecosystems;significantly affect the productivity of ecosystems and the potential for carbon sequestration.The study taking Pinus armandii and Quercus aliena var.acuteserratain at different age groups in Qinling Mountain as research objects.Based on field investigation and laboratory analysis,we analyzing the species composition,the contents and density of soil organic carbon?SOC?and soil total nitrogen?STN?.The study clarified the characteristics of community composition,organic carbon,total nitrogen of P.armandii and Q.aliena var.acuteserratain at different age groups.The main findings are as follows:?1?The species diversity index of P.armandii and Q.aliena var.acuteserratain was inconsistent.In the shrub layer of Q.aliena var.acuteserratain,the Richness index decreased with the increase of age.Simpson index decreased first and then increased with the growth ages then the near-mature forest reached the maximum.The Shannon-Wiener index was opposite with the Simpson index.In the shrub layer of P.armandii,the Richness index showed middle age forest>mature forest>young forest>near-mature forest.And the Simpson index of shrub layer increased first then decreased with the increase of age,the middle age forest reached the maximum the Shannon-Wiener index opposite with the Simpson index.?2?The contents of SOC of Q.aliena var.acuteserratainin and P.armandii were 17.61²8.31 g/kg,18.11²8.30 g/kg,and it increased with the age in the same soil depth.At the same age,the content of SOC was reduced with the increase of soil depth.The content of organic carbon in the litter layer of Q.aliena var.acuteserratainin was 260.09³16.96 g/kg,which increased with the age.Different decomposition states had different regularities.The SOCD in Q.aliena var.acuteserratainin and P.armandii were 83.32¹17.33 t·hm^-2,80.25¹19.08 t·hm^-2,which increased with the age.The soil organic carbon density between Q.aliena var.acuteserratainin and P.armandii had no significant differences.?3?The STN content of Q.aliena var.acuteserratainin was 1.54¹.94 g/kg,and STND was 6.41⁸.47 t·hm^-2,which increased first and then decreased with the increase of age,the near-mature forest reached the maximum.The STN content of P.armandii was 1.29².02 g/kg,STND was 5.85⁸.64 t·hm^-2,increased with the age of the forest.The total nitrogen content of Q.aliena var.acuteserratainin on litter layer was 13.12¹6.02 g/kg,and the mature forest was significantly higher than the other age groups,the total nitrogen density increased with the age of the stand.The total nitrogen content and density of P.armandii on litter layer increased first and then decreased with the age,the content reached the maximum at near-mature forest,while the density reached the maximum at middle age forest.?4?There was a significant positive correlation between forest age,tree layer biomass,basal area and SOC content and density.Soil bulk density,tree layer density had negatively correlated and to SOC content and density.There were significant differences in SOC and TN in different stands.The C:N of Q.aliena var.acuteserrata were significantly negatively correlated with soil TN content and density.The stand age,soil bulk density,the tree layer density,biomass,SOC density and content had significant correlation with soil total nitrogen content and density.