A challenge for understanding the carbon starvation effect on terrestrial carbon cycle by SEIB-DGVM

Abstract:

Drought give a great impact on the plant growth as one of the largest components in global carbon cycle. However, it is challenging to estimate when and where the ecosystem will change caused by drought mainly because the mechanism of how plants are killed due to drought is poorly understood. Nowadays, the conceptual “carbon starvation” as one of mechanism after drought is giving much attention (McDowell et al., 2008). In plants, some parts of carbon absorbed by photosynthesis are stored as nonstructural carbon (NSC). When the photosynthesis rate declines and most of NSC are used for respiration, carbon starvation would be observed. However, where plants are killed and how carbon cycle of the globe will change due to carbon starvation in the future are hardly estimated. The objectives of the research are to apply the process representing carbon starvation to ecological model and expect the potential effect of carbon starvation 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 plants each day. When photosynthesis rate decline, NSC compensates for maintenance respiration and gradually close to zero. And if NSC is zero, plants are killed due to carbon starvation. We used Model for Interdisciplinary Research on Climate- Earth System Model (MIROC-ESM, Watanabe et al, 2011）as a climate date. And I calculated from 1850 to 2005 for an historical scenario and from 2006 to 2100 for a future scenario. The historical scenario follows three passes during future scenarios: control, RCP2.6 and RCP8.5. I compared how much the effect of carbon starvation depends on the strengths of climate change.