A prognostic phenology scheme for global terrestrial carbon cycle models

Abstract

Prognostic and mechanistic schemes for the determination of plant phenological stages from environmental conditions and the estimation of net primary production NPP are presented.The new schemes account for di erent biomes and are included in a global model of carbon cycling in the terrestrial biosphere.The capability of such a model to simulate the seasonal cycle of atmospheric CO 2 is explored.The model is forced by mean monthly climate variables temperature, precipitation and light and the mean annual CO 2 concentration.It predicts the atmosphere biosphere CO 2 exchange uxes, leaf area index LAI, and the times of budburst and leaf abcission.The predicted variables o er means of validation against data of the observed annual cycle of atmospheric CO 2 concentration and observations of LAI derived from satellite data.Estimated annual NPP of forests appears realistic, however NPP of grass dominated biomes is greatly underestimated.This seems to be related to the fact that belowground biomass is not explicitly considered in the model.The results of a simulation of the seasonal cycle of of atmospheric CO 2 concentration using a three dimensional atmospheric transport model are in satisfying agreement with the observations.