Carbon Density Of Main Forest Types In The Qinling Mountains During Different Periods

In this study,carbon density and soil chemistry properties in different periods were researched in pure forests of Pinus tabulaeformis,Quercus aliena var.acuteserrata,and Pinus armandii,as well as mixed stands of Q.aliena var.acuteserrata and P.tabulaeformis,Q.aliena var.acuteserrata and P.armandii at Huoditang forest region in the Qinling Mountains.Furthermore,the results of 2013 and 2018 were compared.The results are as follows:1.Compared the carbon density of different forests of 2013 with 2018,the carbon density of the pure forests of P.tabulaeformis,Q.aliena var.acuteserrata,and P.armandii,as well as mixed stands of Q.aliena var.acuteserrata and P.tabulaeformis,Q.aliena var.acuteserrata and P.armandii declined by 6.227 t/hm~2,30.907 t/hm~2,38.671 t/hm~2,26.122t/hm~2,and 16.000 t/hm~2 respectively.There were significant differences among the carbon density of different forests.On the whole,the carbon density of pure forest decreased more than that of the mixed forest.The carbon density of the pure forests of P.tabulaeformis was higher than that of mixed stands between Q.aliena var.acuteserrata and P.tabulaeformis.2.There were significant differences in the physicochemical properties for five types of soil:the pH value from 5.20~6.21 to 5.42~6.56,available nitrogen from 76.883~207.492mg/kg to 38.927~177.751 mg/kg,nitrate nitrogen from 1.290~10.183 mg/kg to1.364~20.323 mg/kg,ammonium nitrogen from 12.477~21.297 mg/kg to 4.343~29.619mg/kg,organic matter from 22.722~60.586 g/kg to 9.351~47.962 g/kg respectively.There were significant differences in the physical and chemical properties of soils in different forest types.In addition to the content of P.armandii,the soil pH of the other four forest types decreased.The ammonium nitrogen and organic matter contents of the five forest types decreased in different degrees.3.The carbon density of P.tabulaeformis forest was affected by the concentrations of soil total nitrogen,organic matter,available phosphorus and pH.The carbon density of P.armandii was mainly affected by the concentrations of soil available potassium and available nitrogen.The carbon density of Q.aliena var.acuteserrata was mainly affected by the concentrations of soil pH,total phosphorus and available phosphorus.The carbon density of the mixed stands of Q.aliena var.acuteserrata and P.armandii was affected by the concentrations of soil total phosphorus,total nitrogen,pH and total potassium.The carbon density of the mixed stands of Q.aliena var.acuteserrata and P.tabulaeformis was greatly affected by soil total nitrogen,total phosphorus,available phosphorus,pH and available potassium.There was significant positive correlation between carbon density of shrub layer and soil organic matter for the five forest types,and there was no significant correlation between carbon density of arbor layer and carbon density of herb layer and soil organic matter.