Simulating the impact of land use change on ecosystem functions in data-limited watersheds of Mountainous Mainland Southeast Asia

The presented PhD thesis deals with the development of new modelling approaches and application procedures to simulate the impact of land use change (LUC) on soil fertility, carbon sequestration, soil erosion and sediment deposition under data-limited conditions in Mountainous Mainland Southeast Asia. The first study investigated if qualitative datasets derived during participatory processes can be used to parameterize the spatially-explicit, soil fertility-driven FALLOW (Forest, Agroforest, Low-value Landscape Or Wasteland?) model for a case study village in North-western Vietnam. The second study examined the effects of LUC on the provisioning of long-term carbon sinks illustrated for a watershed in Northern Thailand using the Dyna-CLUE (Dynamic and Conversion of Land use Effects) model to simulate different LUC trajectories building on stakeholder-based scenario assumptions and current LUC trends. The third case study examined the impact of LUC on soil erosion and sediment deposition patterns in a small watershed of mountainous Northern Vietnam using a newly developed dynamic and spatially-explicit erosion and sediment deposition model (ERODEP), which was further coupled with the LUCIA (Land Use Change Impact Assessment) model. As a general finding of this study, it is concluded that environmental modellers, decision makers and local stakeholders have to be aware of the trade-offs between model complexity, model input demands, and simulated output reliability. Modelling-based investigations in data-limited areas should always combine scientifically-based approaches with participatory procedures, as scientific assessment can support environmental policy-making, but stakeholders' decision will finally determine the provisioning of ecosystem functions in the long run.