Soil organic carbon mineralization, microbial biomass carbon and metabolic quotient in soils were determined to understand the effects of litter on soils in natural evergreen broadleaved forest, Sassafras tzumu planta...Soil organic carbon mineralization, microbial biomass carbon and metabolic quotient in soils were determined to understand the effects of litter on soils in natural evergreen broadleaved forest, Sassafras tzumu plantation and Cryptomeria fortunei plantation. Soils were collected in the 0～20 cm layer and incubated for 15, 30, 45, 60, 75 and 90 days in the laboratory at 25 ℃ with natural water content and different litters. The results indicated that organic carbon mineralization rate, microbial biomass carbon and metabolic quotient in soils showed the ranked order of natural evergreen broadleaved forest > Sassafras tzumu plantation > Cryptomeria fortunei plantation when the forest litter was not added to the soil. The added forest litter increased the organic carbon mineralization rate, microbial biomass carbon and metabolic quotient in soils regardless of the forests. Comparing with the litter from the Sassafras tzumu plantation and Cryptomeria fortunei plantation, the litter from the natural evergreen broadleaved forest led to higher organic carbon mineralization rate, microbial biomass carbon and metabolic quotient in soils. The results suggested that the artificial regeneration of the natural evergreen broadleaved forest into the Sassafras tzumu plantation and Cryptomeria fortunei plantation might lead to the low organic carbon mineralization, microbial biomass carbon and metabolic quotient in soils.展开更多
The current trend of forest management in many countries is reduced use of clear-felling and planting, and increased use of continuous cover management. In Finland, the new forest act of 2014 made all types of cutting...The current trend of forest management in many countries is reduced use of clear-felling and planting, and increased use of continuous cover management. In Finland, the new forest act of 2014 made all types of cuttings equally allowable on the condition that if the post-cutting residual stand basal area is too low, the stand must be regenerated within certain time frame. Forest landowner can freely choose between even-and uneven-aged management. This study developed a method for opti-mizing the timing and type of cuttings without the need to categorize the management system as either even-aged or uneven-aged. A management system that does not set any requirements on the sequence of post-cutting diameter distributions is called any-aged management. Planting or sow-ing was used when stand basal area fell below the required minimum basal area and the amount of advance regeneration was less than required in the regulations. When the cuttings of 200 stands managed earlier with even-aged silviculture were optimized with the developed system, final felling followed by artificial regeneration was selected for almost 50%of stands. Reduction of the minimum basal area limit greatly decreased the use of artificial regeneration but improved profitability, suggesting that the truly optimal management would be to use natural regeneration in financially mature stands. The optimal type of thinning was high thinning in 97-99%of cases. It was calculated that the minimum basal area re-quirement reduced the mean net present value of the stands by 12-16%when discount rate was 3-5%.展开更多
文摘Soil organic carbon mineralization, microbial biomass carbon and metabolic quotient in soils were determined to understand the effects of litter on soils in natural evergreen broadleaved forest, Sassafras tzumu plantation and Cryptomeria fortunei plantation. Soils were collected in the 0～20 cm layer and incubated for 15, 30, 45, 60, 75 and 90 days in the laboratory at 25 ℃ with natural water content and different litters. The results indicated that organic carbon mineralization rate, microbial biomass carbon and metabolic quotient in soils showed the ranked order of natural evergreen broadleaved forest > Sassafras tzumu plantation > Cryptomeria fortunei plantation when the forest litter was not added to the soil. The added forest litter increased the organic carbon mineralization rate, microbial biomass carbon and metabolic quotient in soils regardless of the forests. Comparing with the litter from the Sassafras tzumu plantation and Cryptomeria fortunei plantation, the litter from the natural evergreen broadleaved forest led to higher organic carbon mineralization rate, microbial biomass carbon and metabolic quotient in soils. The results suggested that the artificial regeneration of the natural evergreen broadleaved forest into the Sassafras tzumu plantation and Cryptomeria fortunei plantation might lead to the low organic carbon mineralization, microbial biomass carbon and metabolic quotient in soils.
文摘The current trend of forest management in many countries is reduced use of clear-felling and planting, and increased use of continuous cover management. In Finland, the new forest act of 2014 made all types of cuttings equally allowable on the condition that if the post-cutting residual stand basal area is too low, the stand must be regenerated within certain time frame. Forest landowner can freely choose between even-and uneven-aged management. This study developed a method for opti-mizing the timing and type of cuttings without the need to categorize the management system as either even-aged or uneven-aged. A management system that does not set any requirements on the sequence of post-cutting diameter distributions is called any-aged management. Planting or sow-ing was used when stand basal area fell below the required minimum basal area and the amount of advance regeneration was less than required in the regulations. When the cuttings of 200 stands managed earlier with even-aged silviculture were optimized with the developed system, final felling followed by artificial regeneration was selected for almost 50%of stands. Reduction of the minimum basal area limit greatly decreased the use of artificial regeneration but improved profitability, suggesting that the truly optimal management would be to use natural regeneration in financially mature stands. The optimal type of thinning was high thinning in 97-99%of cases. It was calculated that the minimum basal area re-quirement reduced the mean net present value of the stands by 12-16%when discount rate was 3-5%.
