The individual-based forest landscape and disturbance model iLand: Overview, progress, and outlook

Forest ecosystems are changing rapidly, and landscape-level processes such as disturbance and dispersal are key drivers of change. Consequently, forest landscape models are important tools for studying forest trajectories under changing environmental conditions and their impacts on ecosystem service provisioning. Here, we synthesize 12 years of development and application of the individual-based forest landscape and disturbance model iLand. Specifically, we describe the fundamental model logic and give an overview of model components introduced over the years. Additionally, we outline how to initialize, evaluate and parameterize the model for new applications. iLand is a process-based forest landscape model that simulates forest dynamics at the level of individual trees. It accounts for continuous processes (tree growth, mortality, and regeneration) as well as discontinuous disturbances (wind, wildfire, and biotic agents) and forest management. Simulations span multiple spatial and temporal scales, from individual trees to landscapes of 105 hectares, and from hourly disturbance dynamics to centuries of forest development. Environmental conditions are represented by daily climate data and high-resolution soil information. The model was designed for flexibly addressing a wide range of research questions, features a rich graphical user interface and comprehensive scripting support. The model is open source and comes with extensive online model documentation. iLand has hitherto been applied in 50 peer-reviewed simulation studies across three continents. Applications primarily focused on the effects of climate change, disturbances and forest management on forest dynamics, ecosystem service provisioning and forest biodiversity. Future model development could address the representation of belowground processes, biotic interactions, and landscape dynamics beyond forest ecosystems. We conclude that process-based simulation of landscape-scale forest dynamics at the level of individual trees has proven a valuable approach of forest landscape modeling.