O. Janne Kjønaas
Seniorforsker
Sammendrag
Understanding long-term effects of clear-cutting on current soil carbon (C) fluxes in boreal forests is important in the perspective of global C cycling and future forest management decisions. We studied twelve pairs of forest stands in South-Eastern Norway, each comprised of one previously clear-cut stand and one near-natural stand with similar macroclimate, topography and soil properties. We measured aboveground tree litterfall continuously during two consecutive years and soil respiration fluxes monthly during the snow-free period of one year. Ground vegetation litterfall was estimated from destructive biomass sampling. The previously clear-cut stands had on average 12 % higher annual soil respiration rates, 20 % greater tree litterfall, and tended to have greater total aboveground litterfall (12 %), while the near-natural stands had greater litterfall from ground vegetation (45 %). Litterfall from ground vegetation was strongly linked with below-canopy light transmission, but the contribution of this flux to the total aboveground litterfall was minor. Soil respiration rates were related to microclimate, nitrogen concentration in aboveground tree litter and tree basal area. Though, only basal area could be linked to management type differences in soil respiration, that likely has additional unidentified drivers. We found similar temperature sensitivities of soil respiration in the two management types. We emphasise that age of the dominating trees is an integrated part of the differences between these two types of forest stands. Jointly, our results suggest limited differences in the current net soil C balance of near-natural and previously clear-cut stands.
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Lisa Fagerli Lunde Tone Birkemoe Anne Sverdrup-Thygeson Johan Asplund Rune Halvorsen O. Janne Kjønaas Jenni Nordén Sundy Maurice Inger Skrede Line Nybakken Håvard KauserudSammendrag
Boreal forests are important carbon sinks and host a diverse array of species that provide important ecosystem functions.Boreal forests have a long history of intensive forestry, in which even-aged management with clear-cutting has been thedominant harvesting practice for the past 50–80 years. As a second cycle of clear-cutting is emerging, there is an urgentneed to examine the effects of repeated clear-cutting events on biodiversity. Clear-cutting has led to reduced numbers ofold and large trees, decreased volumes of dead wood of varied decay stages and diameters, and altered physical andchemical compositions of soils. The old-growth boreal forest has been fragmented and considerably reduced. Here,we review short- and long-term (≥50 years) effects of clear-cutting on boreal forest biodiversity in four key substrates:living trees, dead wood, ground and soil. We then assess landscape-level changes (habitat fragmentation and edge effects)on this biodiversity. There is evidence for long-term community changes af