Age-class disequilibrium as an opportunity for adaptive forest management in the Carpathian Mountains, Romania

Biomass and species composition of a forest district in the North-Eastern Carpathian Mountains were simulated until 2100 using the forest landscape model LandClim, driven by climate data from three general circulation models that projected the local climate change under the A1B emission scenario. Four different management scenarios were used: business as usual and three adaptive management scenarios characterized by an intensification of interventions: more intense thinnings and shorter rotations. The total biomass at the end of the simulation differed greatly according to the climate scenario but was comparatively much less influenced by the management scenarios. Forest biomass was projected to increase markedly under the model which forecast the lowest climate change (CCSM3), remained approximately constant in the intermediate climate model (ECHAM5) but decreased severely in the hypothesis of the largest climate changes (HadCM3). Our results showed that developments in species composition differed much more between climate change scenarios than between management scenarios. Under moderate and intermediate climate scenarios, changes in species composition occurred principally in harvested stands, while stands not harvested did not display species replacements. Under extreme climate change (HadCM3) on the other hand, the species change occurred even before harvest. The model projections highlight the inadequacy of some species for the new growing and regeneration conditions that accompany the extreme climate scenario. Harvesting can be seen as a chance to undergo active adaptation with respect to species composition.