In forest management and modelling, a shift of emphasis has occurred from productivity in homogeneous canopies towards, e.g., wood quality versus total yield, spatially more explicit models, and growth decline in old-growth forests. These new problems emphasize the hierarchy of the system and interscale interactions. These can be constructively dealt with using a hierarchical-modular approach.
The core of the stand growth models developed by the group are models of individual tree growth throughout the rotation. At this scale, model performance requires (i) realistic long-term dynamic properties, (ii) realistic responses of growth and mortality of competing individuals, and (iii) realistic responses to ecophysiological inputs. The models developed by the group are based on carbon acquisition and allocation, combined with ideas of mutual competition through tree-to-tree interactions. In this approach, finer scale effects are embedded in parameters calculated using more detailed, interacting modules. These include, e.g., (i) the within-year effects of weather on metabolic processes, such as photosynthesis and transpiration (ii) the effects of fast soil processes on nutrient availability, carbon allocation and photosynthesis, and (iii) the utilization of detailed stem structure to predict wood quality.
Härkönen S., Pulkkinen M., Duursma R.A., Mäkelä A. 2010. Estimating annual GPP, NPP and stem growth in Finland using summary models. For. Ecol. Manage. 259: 524-533.
Mäkipää R., Linkosalo T., Niinimäki S., Komarov A., Bykhovets S., Tahvonen O. and Mäkelä A. 2010. How forest management and climate change affect the carbon sequestration of a Norway spruce stand. Journal of Forest Planning.
Duursma, R.A. and Mäkelä A. 2007. Summary models for irradiance interception and photosynthesis of non-homogeneous canopies. Tree Physiology 27:859-870
Kokkila, T., Mäkelä, A. and Franc, A. 2006. Comparison of distance dependent and distance independent stand growth models – is perfect aggregation possible? Forest Science 52: 623-635
Valentine H.T. and Mäkelä A 2005. Bridging process-based and empirical approaches to modeling tree growth. Tree Physiology 25:769–779
Mäkelä, A. 2003. Process-based modelling of tree and stand growth: towards a hierarchical treatment of multi-scale processes. Canadian Journal of Forest Research 33:398-409