[A-CG37] Biogeochemical cycles in Land Ecosystem

[ACG37-12] Incorporating non-structural carbon dynamics in individual-based vegetation model SEIB-DGVM

*Hideki Ninomiya¹, Tomomichi Kato¹ (1.Hokkaido University)

Keywords:Nonstructural carbon, Individual-based model, SEIB-DGVM, Carbon allocation, Vegetation dynamics

To understand the effect of climate change on the terrestrial ecosystem, the response of vegetation to atmospheric carbon is critical. As global warming is getting worse, it would contribute to widespread tree mortality related to drought, increased temperature, pest outbreak to name a few. Then, the tree mortality results in the negative impact on the earth; biological diversity, wild animal habitat, hydrological and carbon cycle, and vulnerability to invasion by unexpected exotic species (Adams et al, 2013). However, it is challenging to estimate the negative impact mainly because the mechanism of how plants are killed is poorly understood. To overcome these tree mortality, trees have grown to control their carbon resources and strategically allocate them to growth, respiration, storage, reproduction, and defense (Hoch et al, 2003; Henrik et al, 2018). The percentage of carbon allocation to each compartment is giving much attention today. Among carbon resources, non-structural carbon (NSC) is commonly considered a repository depending on the balance between the supply of assimilated carbon and carbon demand. Hence, the size of stored C pools can be considered an indicator of the carbon balance of the plant. Additionally, NSC could be the threshold of the conceptual “carbon starvation” as one of the mechanisms after drought (Hoch et al, 2003; McDowell et al., 2008). The objectives of the research are to apply the process representing NSC dynamics to the ecological model and expect the potential effect of NSC in the future.

The process-based Spatially Explicit Individual-Based Dynamic Global Vegetation Model (SEIB-DGVM; Sato et al., 2007), representing three-dimensional tree structure and individual tree growth, was used in this study. In a 30m×30m grid, each plant establishes and dies while sharing incoming solar photons with other plants. Here, we newly introduced a process of accumulating NSC in plants to SEIB-DGVM. Carbon from photosynthesis is mainly allocated to maintenance respiration and growth respiration of plant structure: leaf, stem, and root. In the research, I created a simple NSC pool. All carbon is not consumed but some of them are stored in three organs of plants each day. When photosynthesis rate declines, NSC compensates for maintenance respiration and gradually close to zero. We validated the NSC dynamics at a point and global scale. Firstly, we chose 4 sites representing different plant functional types for the validation: Austria, Swiss, Canada, and Panama, and used observation data as climate data. Secondly, we validated them depending on climate zones: tropical, temperate, and boreal. The climate data for global is Model for Interdisciplinary Research on Climate- Earth System Model (MIROC-ESM, Watanabe et al, 2011). The study contributes to improving the physiological leaf life cycle of the model. In addition, we can understand how NSC will affect the vegetation distribution, gross primary production (GPP), net primary production (NPP) in the future.