Upscaling to Higher Levels of Organisation

Abstract

Upscaling of the models of the annual cycle of boreal and temperate trees to higher levels of organisation is briefly discussed. The models of the annual phenological cycle (Chap. 3), the annual cycle of photosynthesis in evergreen conifers (Chap. 4), and the annual cycle of frost hardiness (Chap. 5) address the modelled phenomena at the level of individual trees. Over the last decades, these models have been increasingly introduced as sub-models into large-scale process-based ecosystem models. In particular, models for the annual cycle of photosynthesis have often been used as sub-models. A simulation study reviewed here shows that unless the boreal restrictions described by the annual cycle model are taken into consideration, a drastic overestimate of the Gross Primary Production of the tree stand is obtained in simulations. About 15 years ago the models of the annual cycle were upscaled to the continental level in modelling the geographical ranges of tree species. The large-scale models thus refined predicted the geographical ranges of tree species accurately, suggesting that the seasonal phenomena of trees are major determinants of the geographical ranges of the tree species. While this approach opens an entirely new promising avenue for research, the annual cycle models applied in these studies still require further development for better realism. These models have also been addressed to a limited extent in the Dynamic Global Vegetation Models, but in this case, too, the annual cycle models applied evidently require further development.