[A-CG39] Biogeochemical cycles in Land Ecosystem

[ACG39-05] Modeling of ecosystem-level monoterpene emission in a Larch forest by a VISIT model

*Zhanzhuo Chen¹, Tomomichi Kato^2,3 (1.Graduate School of Global Food Resource, Hokkaido University, 2.Research Faculty of Agriculture, Hokkaido University, 3.Global Center for Food, Land, and Water Resources, Hokkaido University)

Keywords:Process-based modeling, Monoterpene emission, Plant physiology, VISIT model

Globally, Biogenic Volatile Organic Compounds (BVOC) are the dominate sources of Volatile Organic Compounds (VOC) affecting global atmospheric environment, which mainly originate from vegetation activities in terrestrial environment. Monoterpene, as the BVOC with typical storage process mainly from larch forests, can influence the process of generating secondary organic aerosols (SOA), causing variability in climate particularly in temperature sensitive areas. However, previous modeling studies rarely simulated monoterpene emission at daily range for long term. Therefore, here we developed a novel process-based module in VISIT model based on the half-hourly monoterpene emission data from Larix kaempferi forest at Mt. Fuji, Japan. To build the module, we consider the ecosystem level monoterpene production, storage, and emission as three main processes of this module. Regarding the stresses, except for temperature and light, we also take accounts of CO₂ concentration and soil water content as the factors to influence the process of monoterpene production. Moreover, we explore the best parameter group for optimal monoterpene residence time (rt) and residence fraction (rf) in this ecosystem, as the main step of model calibration in this study. Our results indicate when rt and rf are 160 days and 0.7, the root mean squared error (RMSE) shows the best with observational data. Typically, VISIT model presents a better performance in annually average result (0.64 nmol/m²/s) than that (0.52 nmol/m²/s) simulated by temperature-dependent model G93 comparing with average observational result (0.62 nmol/m²/s). We also find VISIT model can perform a more effective response to diurnal change of temperature and light than simulating by G93 model. We believe our modeling work can be good example to estimate monoterpene emission in Siberia larch or other areas with such typical vegetation. However, we still need more validation data for model calibration for different plant function type (PFT) if simulating at global scale.