Developing an integrated terrestrial ecosystem model for global changing predictions

1. Developing an integrated terrestrial ecosystem model for global changing predictions 陸域統合モデルへの結合を念頭にした 植生動態モデルの構築（設計と進捗状況の報告） Hisashi SATO (FRSGC) & Takashi KOHYAMA (Hokkaido Univ.)

2. Toward developing the land surface model Land surface physical process model Land surface carbon cycle model Vegetation dynamics model For simulating long time scales, vegetation dynamics model must be added to predict changes in vegetation distribution 原図：伊藤昭彦

3. * Feature of dynamics modules within previous DGVMs TRIFFID HYBRID 3.0 ロトカ・ヴォルテラ方程式を用いて、大胆なパラメタライズを断行。これを、陸上植生の様に本質的に混ざり合うことのないシステムに対して適用することは適切ではない。 唯一、個体ベースモデル。ただし、FORSKAという極めて原始的なモデルを使用しており、また植生内の水平方向の地理的ヘテロ性も扱っていない。要するに1 Patchモデルをグリッド毎に複数走らせ、その平均値をグリッドを代表する値として用いている。 IBIS/ LPJ/ SDGVM 水平方向のヘテロ性を無視したArea-based model。各PFTの優先度を葉群投影被度で表現し、これが1.0を超えた段階で、PFT間の光を巡る競争が生じる。 Limited computation power inhibit to directly incorporate spatial hetero-structure of vegetations into the DGVMs. * Dynamic Global Vegetation Models

4. However, spatial hetero-structure plays a central role in vegetation dynamics Gap dynamics Competition among saplings Gap formation 例えばPacala et al.(1995)は、光環境を空間的に平均してしまうモデルでは樹種の交代の様子が変化するだけでなく、総バイオマスも実際の森林の半分くらいになってしまうことを示している。ギャップの下にはとても明るい環境があるはずなのに、これを暗いところと併せて平均してしまうことで、ギャップ内での森林の再生が遅れてしまうためである。この結果は、森林の水平方向の構造を無視してしまうことの危険性を示唆している（竹中2002 より引用）

5. Feature of the DGVM (1) Major advances from the previous DGVMs * • Individual Based Model (except for herbaceous PFTs) • Explicitly simulate spatial structures of vegetations A snap shot of the simulated forest stand (30m×30m). Individual tree is composed of crown, stem, and root. Shape of crown and stem are approximated by cylinder. --- Individual characteristics for woody PFTs --- Crown : biomass, diameter, depth Stem : biomass, height, sapwood & heartwood diameter Root : biomass + reserve resource for sprouting * Plant Functional Types

6. Feature of the DGVM (2) By explicitly treating forest 3D structure, the model can reasonably calculate individual light conditions Estimate light distribution within canopy using leaf area concentration and light attenuation index Calculate NPP, and adjust bole height by perishing deficit crown layer Estimate light intensity on the top of the crown by using canopy location within the forest stand (SORTIE like) Estimated light intensity NPP 0.0 To avoid ‘edge effect’, this scanning is performed among replicated forest stands, which surround the examining area.

7. Feature of the DGVM (3) Characteristics of herbaceous PFTs Leaf : biomass in a forest stand Stem : biomass in a forest stand Root : biomass in a forest stand Competition between woody PFTs and herbaceous PFTs 木本PFTsの定着率 Grass layer 草本PFTsのバイオマス Grass layer can only use light on the forest floor Luxuriant grass layer inhibit establishment of woody PFTs.

8. Output example (1): Dynamics of temperate summer-green forest Current version uses ・tentative modules for daily processes, mortality, and phenology ・parameters, which have not adjusted yet

9. Output examples (2): Dynamics of temperate summer-green forest 200 years Litter production ( Kg / ha year ) Leaf Area Index (m2 / m2 ) Biomass (Kg / ha ) Sum of stem diameter at breast height ( m / ha )

10. To see more details of the DGVM …. Module that comprise the dynamic global vegetation models, and its computation time steps. Use modules of Sim-CYCLE

11. Scheme for connecting phenology module and photosynthesis module

12. Simulation procedure (1) Simulation will be conducted on the T42 global grid (128×64), each of which includes 10 replication forest stands. Thus, assuming 1/3 of the earth surface is terrene, about 27000 independent forest stand will be independently simulated. To date, this would be the most complex ecosystem model that have ever made. 小サイズの林分を複数シミュレートさせる主な理由としては、攪乱の問題があげられる。例えば寒帯林で頻発する森林火災は、一度生じると、シミュレートしている林分の大きさが30×30ｍだろうが1haだろうが、その殆ど全てが壊滅してしまう。このように機会的に大きく変動する単一の林分をもって、グリッドの代表値とさせることは適当ではない。

13. Simulation procedure (2) Simulation 1 (free seed dispersal) assumes that all PFTs establish all grid, irrespective of previous or current vegetation distribution Simulation 2 (no seed dispersal) assumes that PFTs that currently distribute for each grid only establish in the grid permanently The former simulation should provide maximum estimate of vegetation change, while the latter should provide minimum estimate.

14. Procedure for parameter estimation and tuning (1) (2) (3) (4) (5) Estimate parameters and algorithm of a tree growth so that tree-form and leaf-density are reasonably simulated for each PFT Estimate dynamics parameters (Establishment, Mortality, Disturbance): so that density and age distribution of tree are reasonably simulated when only one PFT composes the forest Estimate metabolic parameters (Photosynthesis, Respiration, Allocation): So that biomass, LAI, and distribution of DBH are reasonably simulated. This will be conducted on forest that was composed of only one PFT. By repeating above (2) and (3), convergence parameters Conduct test run on global grid then examine that distribution of vegetation and GPP at equilibrium are reasonably simulated.

15. Schedule Complete to develop the the DGVM program except daily processes Link it with daily process modules of Sim-CYCLE Parameter estimation and tuning Vectorize the program and conduct simulation at global scale on the earth simulator ・ within Oct ・ 2 to 4 month ・ 1 to 3 month ・ ?