Changes in allometric relations of mangrove trees due to resource availability - A new mechanistic modelling approach

Models based on allometric responses to competing neighbours and environmental conditions in mangrove forests are increasingly available. However, the improvement of these models requires a mechanistic understanding of how individual trees allocate biomass. This study introduces a new tree model (BETTINA) focusing on this issue. It is designed to investigate the response of trees in terms of biomass allocation patterns to environmental conditions. Additionally, it is suitable as a component of an individual-based mangrove stand model. BETTINA describes the plasticity of trees in growth patterns depending on their below-ground resource uptake. In contrast to the existing mangrove stand models, BETTINA focusses explicitly on the processes leading to variation in resource availability. Based on the physical principle of osmotic potential of solutions, the direct influence of salinity on plant water availability is considered. Allometric model parameters are not restricted to only the above-ground measures of trees' traits (such as stem diameter and height), but also characterize below-ground biomass. Within BETTINA these measures are not limited to predefined empirical maximum values, but are the result of and depend on environmental conditions. The model is suitable to explain allometric measures and relations in dependence on total plant size and environmental conditions (for now salinity and light), and has a great potential for a physiologically and physically based improvement of plant component related biomass estimations. (C) 2014 Elsevier B.V. All rights reserved.