Individual-based modelling of the Arctic treeline

LAVESI is an individual-based spatially-explicit model that simulates currently the life cycle of larch species as completely as possible from seeds to mature trees. It was set up to improve our understanding of past and future treeline dynamics under changing climates focusing on the open larch forest ecosystem in Arctic environments which are underlain by permafrost. The relevant processes (growth, seed production and dispersal, establishment and mortality) are incorporated as submodules which are parameterized on the basis with field evidence complemented with data from literature. Simulation runs proceed in yearly time steps and are forced by monthly temperature and precipitation time series.

The model is programmed in C++ using standard template libraries and the code is parallelised to enable fast computation. This and its modular structure allow a straightforward development so that further extensions can easily be implemented. The major recent model enhancements include the representation of further tree taxa so that the model can be applied on larger spatial domains including more southern boreal forests. Additionally, a complete genetic inheritance among simulated individuals was achieved which allows a novel and more realistic implementation of seed and pollen dispersal kernels to be validated by validation with genetic data. This will help to reliably disentangle the historic and future migration dynamics of the Siberian treeline.