Modelling of a diffusive Lotka-Volterra-System: the climate-induced shifting of tundra and forest realms in North-America

A Lotka-Volterra Vegetation System (LVVS) was modelled in this work in two dimensions and applied to various climate scenarios. The parameters of a diffusive and competitive tundra/forest system were deduced from ecological observation data for a 28°×28° area in North-America. The transient behaviour of the LVVS was studied for present and future climate. Eventually we accomplished the simulations for a climate after a ‘temperature shock’. In all three cases the vegetation boundary does not move within the spatial resolution of the Matthews Map (1985) [Matthews, E., 1985. Atlas of Archieved Vegetation, Land-Use and Seasonal Albedo Data Sets. NASA Technical Memorandum 86199, GSFC Institute for Space Studies] that is 50 km in 100 years. The results are reconcilable with the one-dimensional model of Helmes (1993) (unpublished results). Note that the climate-induced shifting of vegetation zones is overestimated by some rule-based, steady-state models that predict shifts of the tundra-forest boundary to northern regions of about 540 km for a future climate.