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Abstract:
Forest management influences several ecosystem
processes, including carbon exchange between forest
ecosystem and atmosphere. The aim of this paper was to
study the carbon cycle over different age classes of two
managed forests in the Italian Alps through direct measurements
and modelling. For this purpose, ecosystem
carbon dynamics of a beech forest (Fagus sylvatica L.) and
of a spruce forest (Picea abies (L.) Karst.) were investigated
using a chronosequence approach. In both forests,
five forest development stages were identified (thicket, pole
wood, young forest, mature forest and the regeneration
phase) with an age spanning from 42 to 163 years for the
beech forest and from 35 to 161 years for the spruce forest.
Measured total ecosystem carbon stock increased up to
80–100 years, with a mean of 232 MgC ha-1 in the beech
forest and of 299 MgC ha-1 in the spruce forest. Calculated
net ecosystem production (NEP) was found to
decrease linearly with age and had an average value of 2.2
and 4.4 MgC ha-1 year-1 for beech and spruce forest,
respectively. Model simulations reported an increase in
NEP till 50–60 years followed by a decrease thereafter.
The model also predicted a negative NEP for a short period
(8–11 years) after the seed cut. Aboveground biomass was
the main driver of carbon accumulation while soil carbon
was not significantly influenced by both age and management
system. Moreover, measured data and model showed
that the applied shelterwood system allowed for a rapid
recovery of the ecosystem after the disturbance (i.e. seed cut), bringing back forest to act as C sink in few years.