Carbon Density Of Mixed Plantations Of Pinus Massoniana And Schima Superba In Different Proportions

Forests,as a principal component of terrestrial ecosystems,are the largest carbon pool.Forest ecosystems play an important role in global carbon cycling and mitigating climate warming.Carbon density is the basis for accurately estimating the carbon sequestration capacity of forest ecosystems,which can provide scientific basis for carbon sink forestry.This study investigated aerially seeded Pinus massoniana plantations in Xing’guo County.According to the tree species mixed proportion,the stands were divided into four types,which were type Ⅰ（ten Pinus massoniana）,type Ⅱ（eight Pinus massoniana and two Schima superba）,type Ⅲ（seven Pinus massoniana and three Schima superba）and typeⅣ（six Pinus massoniana and four Schima superba）.The changes of carbon density in tree layer,understory vegetation layer,litter layer,soil layer and total stand were discussed,and the corresponding management measures were put forward according to their change characteristics,by setting up the typical sample plots.The main results were as follows:（1）Tree layer carbon density of mixed plantations in different proportions ranged from 35.64 t·hm^-2 to 56.04 t·hm^-2 with the descending order of type Ⅳ> type Ⅲ> typeⅡ> type I.It was indicated that the tree layer carbon density increased with the increase of the proportion of Schima superba,but the tree layer carbon density between each type had no significance difference（P>0.05）.（2）Understory vegetation layer carbon density of different types ranged from 0.61t·hm^-2 to 0.86 t·hm^-2 with the descending order of type I> typeⅡ> typeⅢ>typeⅣ.It was indicated that the understory vegetation layer carbon density increased with the decrease of the proportion of Schima superba,but the understory vegetation layer carbon density between each type had no significance difference（P>0.05）.Litter layer carbon density of mixed plantation in different proportions ranged from 0.32 t·hm^-2 to 1.29 t·hm^-2 with the descending order of type Ⅳ> type Ⅲ> type Ⅱ> type I,which indicated that the litter layer carbon density increased with the increase of the proportion of Schima superba,and the difference of Schima superba proportion had a significant influence on litter layer carbon density（P<0.05）.（3）Carbon density of 0-10 cm soil layer ranged from 8.21 t·hm^-2 to 17.08 t·hm^-2.The soil carbon density of type IV was significantly higher than type I and type II（P<0.05）,and type III was significantly higher than type I（P<0.05）.And 10-20 cm ranged from6.66 t·hm^-2 to 12.31 t·hm^-2,while type III and type IV were significantly higher than type I（P<0.05）.Soil carbon density of 0-20 cm showed that type Ⅳ> type Ⅲ> type Ⅱ> type I.（4）Total stand carbon density of mixed plantations in different proportions ranged from 51.69 t·hm^-2 to 87.34 t·hm^-2,and it was indicated that the total stand carbon density increased with the increase of the proportion of Schima superba.Among them,the total carbon density of type IV was significantly higher than type I and type II（P<0.05）,but there was no significant difference with type III（P>0.05）,and there was no significant difference between type I,II and III（P>0.05）.With the increase of the proportion of Schima superba,there was no significant change in the proportion of the tree and soil layerto the total stand carbon density,whereas the trend of understory vegetation and litter layer showed rising and declining respectively.