Long term (81 years) C sequestration is slightly higher in an even-aged compared to an uneven-aged spruce stand; The even-aged stand has at 81 years age a slightly lower soil C content than the uneven-aged stand; Present C fluxes indicate that the difference in long term C sequestration will increase in favour the even-aged stand if final felling is postponed.
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This investigation compares present C stores, fluxes and historic tree C sequestration in an uneven-aged and an even-aged Norway spruce stand under similar high productive soil conditions in south-eastern Norway. A selection cutting system has been performed in the uneven-aged forest stand for 81 years and the even-aged stand was established after clear-cutting 81 years ago. Timber productivity has been measured in the uneven stand for 81 years and in the even-aged stand for 52 years. C storage was determined based on tree measurements, tree biomass functions, soil samples and C analyses from trees and soil. Litter fall was sampled during one year and CO2 efflux from the soil was measured during one growing season. The present tree C storage (including roots) was 210 Mg C ha-1 in the even-aged stand and 76 Mg C ha-1 in the uneven-aged stand, while the corresponding figures for C in the soil was 178 and 199 Mg C ha-1. The long term timber production in the uneven-aged stand was measured to be 95% of the even-aged stand and the difference in net C sequestration was 37 Mg ha-1 in an 81 year period in favour the even-aged stand. The highest present CO2 efflux from soil was measured in the even-aged stand. The total net C sequestered in trees during 81 years minus the present soil C-stock accounts to 16 Mg ha-1 in favour the even-aged system