# Simulating Forest Dynamics of Lowland Rainforests in Eastern Madagascar
## 1 Introduction
Difficulties include: (a) abstracting the immense tree species diversity in tropical rainforests; (b) in terms of which of the rarer species to include, many rainforests have still not been fully described and species lists are incomplete; (c) species parameterization is vexed by the absence of life history, allometric, and phenological information on some, if not many, of the individual tree species; (d) the large variation in growth rates and growth forms of tree species of similar size, along with a general lack of interpretable tree rings; (e) comparatively little information on seed dispersal mechanisms and seed bank longevity; (f) limited information on natural disturbance recovery rates and patterns, as well as how individual tree species respond to changing climatic conditions; and (g) lack of long term monitoring data relative to the age of old growth forests [11; 15; 16; 17]. These considerations, combined with the challenges of achieving the appropriate measurements needed for parameterizing models in forested ecosystems that are often difficult to access, have given rise to the development of different classes of ecological models. The adaptation of IBGMs toward accurate simulation of tropical forests has brought about a new set of challenges. Chiefly among them are how to simulate the high levels of biotic diversity and endemism that characterize forests of the tropics. The significance of and the underlying processes that cause the coexistence of the high levels of tree diversity found in tropical rainforests are not well understood; thus, creating forest models that can simulate the many but rarely occurring species is difficult to achieve. To resolve this, the individual-based FORMIND forest growth model [17] takes a different approach from other rainforest models in that it combines aspects of several types of ecological models. The successional status of the forest is driven by canopy gap formation and position, and tree species are aggregated into size and light-requirement-based functional groups. In addition, canopy layer structure and tree growth are calculated based on a biomass balance, using equations for leaf photo-production that are a typical approach of process models [11]. Because of these key features, the model is widely applicable to large areas of tropical rainforests with high levels of accuracy of biomass prediction (see: [18; 19]). The lowland rainforests of Madagascar are a classic example of species-rich ecosystems with more than 297 species per hectare measured in the region of the eastern lowland rainforest study sites. Deforestation across Madagascar's remaining forest ecosystems has been measured at an average rate of 1100 km\({}^{2}\)/year [20] in recent years; with its high degree of endemism and tree species richness, Madagascar is one of the world's most threatened hotspots for terrestrial biodiversity [21]. Based on the assessment (see: [22]) that growth and species distribution within the study site are undergoing and responding to classic gap processes as described by [PERSON] [15; 23], FORMIND is an appropriate forest growth model to parameterize and test for the lowland rainforests of Madagascar. In this study, the FORMIND model is parameterized for Madagascar's lowland rainforest and evaluated. The objectives of this study are to:  
1. Apply forest inventory and growth data from tree species collected in repeat inventory plots in lowland rainforest to calculate model parameters and group species into plant function types (PFTs), in order to test the applicability of the model's functional type classification approach toward accurately simulating key forest structure and attributes in the study forest. 2. Validate FORMIND using an independent forest inventory dataset collected from an additional lowland rainforest study site. 3. Calculate forest productivity estimates for the region by using the forest model.