| Elaeocarpus sylvestris and Castanopsis fissa are the main tree species in non-commercial forests of Xiaoken foresty farm,Shaoguan,Guangdong Province.In this study,the biomass equations for different tree components of the two forests were established with diameter class standard wood method,and the biomass of tree,understory shrub,herb,and litter layers in the two forest ecosystems were estimated.The content,stock and distribution of carbon,nitrogen,phosphorus and potassium in the ecosystem were analyzed,and their stoichiometry characteristics were discussed,which can provide scientific basis for studying carbon stock and nutrient management of non-commercial forests.The results show that:(1)There was a good relationship between the individual tree biomass and the diameter at breast height for different tree components of two tree species,with the coefficient of determination(R~2)was 0.760-0.955.(2)The total biomasses of E.sylvestris and C.fissa ecosystems were 34.90,66.55t/hm~2,respectively,biomass for each layer decreased in the order of tree layer>herb layer>litter layer>shrub layer,among which the biomass of tree layer accounted for 76.7%and 93.3%of the total biomass of E.sylvestris and C.fissa ecosystems,respectively,with the order of stem>branch>root>leaf.(3)The average carbon content of E.sylvestris and C.fissa were 463.79 and 476.65g/kg,respectively,which(g/kg)decreased in the order of shrub layer(480.82)>tree layer(474.79)>litter layer(465.38)>herb layer(434.17)for E.sylvestris,and litter layer(506.11)>shrub layer(483.61)>tree layer(471.81)>herb layer(445.06)for C.fissa.(4)The average nitrogen content of E.sylvestris and C.fissa were 11.32,9.67 g/kg,respectively,which(g/kg)decreased in the order of litter layer(15.27)>herb layer(10.73)>shrub layer(10.29)>tree layer(8.98)for E.sylvestris,and litter layer(13.30)>herb layer(9.98)>shrub layer(8.00)>tree layer(7.38)for C.fissa.The average phosphorus content of E.sylvestris and C.fissa were 0.74 and 0.92 g/kg,respectively,which(g/kg)decreased in the order of shrub layer(0.78)>litter layer(0.76)>herb layer(0.72)>tree layer(0.69)for E.sylvestris,and shrub layer(1.33)>herb layer(1.08)>tree layer(0.71)>litter layer(0.55)for C.fissa.The average potassium content of E.sylvestris and C.fissa were 7.24 and 5.68 g/kg,respectively,which(g/kg)decreased in the order of shrub layer(10.86)>herb layer(9.23)>tree layer(6.13)>litter layer(2.74)for E.sylvestris,herb layer(9.89)>shrub layer(6.73)>tree layer(4.57)>litter layer(1.53)for C.fissa.(5)The soil bulk density in E.sylvestris and C.fissa of the soil layer ranged from 0.95to 1.63 and 1.22 to 1.50 g/cm~3,The value of pH ranged from 3.51 to 3.80 and 3.59 to 3.76,the contents of soil organic carbon ranged from 6.09 to 22.96 and 8.10 to 18.73 g/kg,total nitrogen ranged from 0.67 to 1.68 and 0.78 to 1.54,total phosphorus ranged from 0.45 to0.52 and 0.66 to 0.84 g/kg,total potassium ranged from 20.31 to 22.51 and 17.91 to 19.87g/kg,alkali nitrogen ranged from 56.64 to 155.62 and 75.33 to 143.99 mg/kg,available phosphorus ranged from 73.67 to 530.76 and 164.42 to 428.77 mg/kg,available potassium ranged from 96.50 to 406.58 and 133.98 to 394.08 mg/kg,respectively.(6)The carbon stock per unit area of E.sylvestris and C.fissa ecosystems were 153.03and 219.69 t/hm~2,respectively,with the order of soil layer(136.37)>tree layer(12.85)>litter layer(1.77)>herb layer(1.57)>shrub layer(0.46)for E.sylvestris,soil layer(188.54)>tree layer(29.10)>herb layer(1.13)>litter layer(0.64)>shrub layer(0.27)for C.fissa.The nitrogen accumulation of E.sylvestris and C.fissa were 13.05 and 16.15 t/hm~2,respectively,with the order of soil layer(12.81)>tree layer(0.14)>litter layer(0.05)>herb layer(0.04)>shrub layer(0.01)for E.sylvestris,soil layer(15.87)>tree layer(0.24)>herb layer(0.03)>litter layer(0.01)>shrub layer(0.01)for C.fissa.The phosphorus accumulation of E.sylvestris and C.fissa were 6.78 and 10.00 t/hm~2,respectively,with the order of soil layer(6.753、9.946)>tree layer(0.013、0.025)>herb layer(0.003、0.003)>litter layer(0.002、0.001)>shrub layer(0.001、0.001)for the two ecosystems.The potassium accumulation of E.sylvestris and C.fissa were 302.990 and 263.918 t/hm~2,respectively,with the order of soil layer(302.823、263.716)>tree layer(0.113、0.168)>herb layer(0.037、0.026)>shrub layer(0.012、0.004)>litter layer(0.005、0.004)for the two ecosystems.(7)The C/N,C/P,C/K,N/P ranged from 22.87-236.17,362.35-1482.63,39.27-149.86,6.28-15.84 in the tree layer of E.sylvestris ecosystem,respectively,and ranged from27.59-281.41,435.12-4089.29,71.39-464.70,4.06-18.89,in the tree layer of C.fissa ecosystem,respectively.The C/N,C/P,C/K,N/P ranged from 8.58-13.69,13.24-43.90,0.29-1.02,1.45-3.21,in the soil layer of E.sylvestris ecosystem,respectively,and ranged from 10.32-12.69,12.22-22.38,0.45-0.94,1.18-1.84,in the soil layer of C.fissa ecosystem,respectively.The order of C/N decreased according to tree layer>litter layer>soil layer,whereas C/P,C/K and N/P C/N decreased in the order of litter layer>tree layer>soil layer in E.sylvestris ecosystem,The order of C/N and C/P decreased in the order of tree layer>litter layer>soil layer,whereas C/K and N/P decreased in the order of litter layer>tree layer>soil layer in C.fissa ecosystem.(8)Considering on selection of tree species for the improvement of forest stand,C.fissa should be given priority.Considering on forest management,it is necessary to reasonably control the stand density in order to obtain higher carbon and nutrient stock.According to the soil chemical properties,phosphate fertilizers can be applied appropriately to optimize soil conditions. |
