Influence of tree species on carbon sequestration in afforested pastures in a humid temperate region

Abstract

Objectives This study examines the influence of tree species in relation to biomass and soil C dynamics in plantations established on former pasture land. Data on the C sink capacity of such plantations will provide valuable information for designing improved management strategies for afforestation programmes aimed at mitigating CO2 emissions.

Methods The study was carried in the temperate forest of southern Europe, one of the most productive timber production systems in Europe. The study, designed to control most of the variability at regional level, involved a network of 120 paired plots (former pasture land-new plantations of different ages) established to construct three well-replicated chronosequences of the most common tree species in humid temperate systems.

Results The mean rates of C sequestration (biomass and soil) estimated throughout the rotation ranged between 8.7 and 14.6 Mg C ha−1 year−1 (Eucalyptus nitens>Eucalyptus globulus>Pinus radiata), and the contribution of the soil (forest floor plus mineral soil) ranged from 8 to 18% (Eucalyptus nitens>Pinus radiata>Eucalyptus globulus). The humid temperate climate and the sandy loam texture of the soils favoured large losses of SOC from the uppermost mineral soils during the 10 year after afforestation. The higher loss of SOC in the Pinus radiata soil (26% of initial SOC) than in the Eucalyptus soil (19.45% of initial SOC) was attributed to the lower transfer of organic C to the mineral soil, as a result of the lower litter decomposition rate and the lower belowground litter input from associated vegetation. The rapid development of tree biomass favoured the subsequent C sequestration in biomass and soils.

Conclusion The C sink capacity of forest plantations can be maximized by elongating the rotation length and adopting suitable management strategies for each species. This is especially important in intensive forest plantations in which the high intensity of harvesting may prevent accumulation of SOC in the long term.