Simulation of Net Primary Production (NPP) of Picea abies in southern Sweden : an analysis based on three forest growth models

Abstract: The potential Net Primary Production (NPP) under climate change was simulated by using twoprocess based growth models, 3-PG and BIOMASS. Both models were run for two climatescenarios A2 and B2 during the period 2071-2100 and compared with simulations of referenceclimate (1961-1990). The simulated NPP of the 3-PG model was also compared with simulatedoutput of NPP from the BIOMASS model, for Picea abies (Norway spruce) at Asa in southernSweden. In addition, the simulation results from 3-PG were compared with the biomassproduction of the empirical growth model DT. Special objectives of this study were (i) toestimate 3-PG parameters for Picea abies, (ii) compare the simulated NPP under differentclimate scenarios A2 and B2, (iii) analyze the 3-PG model sensitivity towards change intemperature, rainfall and soil fertility and (iv) to compare the prediction of potential NPPbetween 3-PG and BIOMASS models. Climate data showed an increased precipitation duringwinter season and elevated temperature throughout the whole year. The development of drymass (tones/ha) simulated through 3-PG had good correlation with values simulated throughDT. The R2 value for foliage dry mass, root dry mass, stem dry mass and total dry mass are0.82, 0.94, 0.7 and 0.73 respectively. The relative increase in predicted NPP ranged between26.8-48.4% and 55.5-101.6% for A2 and B2 scenarios, respectively. A sensitivity analysis wasalso conducted for the effect of rainfall, temperature and soil fertility on potential NPPsimulated by the 3-PG model. The relative range of NPP under A2-scenario was 55.5-101.6%for the 3-PG model and 13.3-41.8 for the BIOMASS model. The corresponding value for theB2-scenario was 26.8-48.4 % for 3-PG and 10.7-29.7 for BIOMASS.