Developing an integrated terrestrial ecosystem model for global changing predictions Hisashi SATO (FRSGC) & Takashi KOHYAMA (Hokkaido Univ.) 陸陸陸陸陸陸陸陸陸陸陸陸陸陸陸陸陸 陸陸陸陸陸陸陸陸陸陸 陸陸陸陸陸陸陸陸陸陸陸 ()
Jan 12, 2016
Developing an integrated terrestrial ecosystem model
for global changing predictions
Hisashi SATO (FRSGC) & Takashi KOHYAMA (Hokkaido Univ.)
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)
Toward developing the land surface model
Land surface carbon cycle model
Vegetation dynamics model
原図:伊藤昭彦
Land surface physical process model
For simulating long time scales, vegetation dynamics model must be added to predict changes in vegetation distribution
TRIFFIDHYBRID 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。
Feature of dynamics modules within previous DGVMs
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。
IBIS/ LPJ/ SDGVM
* Dynamic Global Vegetation Models
*
Limited computation power inhibit to directly incorporate spatial hetero-structure of vegetations into the DGVMs.
However, spatial hetero-structure plays a central role in vegetation dynamics
Gap dynamics
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)
Gap formation Competition among saplings
Feature of the DGVM (1)
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.
Crown : biomass, diameter, depth Stem : biomass, height, sapwood & heartwood diameter Root : biomass
+ reserve resource for sprouting
--- Individual characteristics for woody PFTs ---
Major advances from the previous DGVMs
(1) Individual Based Model (except for herbaceous PFTs)(2) Explicitly simulate spatial structures of vegetations
*
* Plant Functional Types
Feature of the DGVM (2)
Estimate light intensity on the top of the crown by using canopy location within the forest stand (SORTIE like)
To avoid ‘edge effect’, this scanning is performed among replicated forest stands, which surround the examining area.
Estimate light distribution within canopy using leaf area concentration and light attenuation index
By explicitly treating forest 3D structure, the model can reasonably calculate individual light conditions
Calculate NPP, and adjust bole height by perishing deficit crown layer
NPP0.0
Estimated light intensity
Feature of the DGVM (3)
Competition between woody PFTs and herbaceous PFTs
Grass layer can only use light on the forest floor
Luxuriant grass layer inhibit establishment of woody PFTs.
Grass layer 草本 PFTs のバイオマス
木本
PF
Ts
の定着率
Characteristics of herbaceous PFTs
Leaf : biomass in a forest standStem : biomass in a forest standRoot : biomass in a forest stand
Output example (1): Dynamics of temperate summer-green forest
・ tentative modules for daily processes, mortality, and phenology・ parameters, which have not adjusted yet
Current version uses
Output examples (2): Dynamics of temperate summer-green forest 200 years
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Litter production ( Kg / ha year )
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1.5
Leaf Area Index ( m2 / m2 )
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Foliage
Stem
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Biomass ( Kg / ha ) Sum of stem diameter at breast height ( m / ha )
Module that comprise the dynamic global vegetation models, and its computation time steps.
Use modules of Sim-CYCLE
To see more details of the DGVM ….
Scheme for connecting phenology module and photosynthesis module
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.
Simulation procedure (1)
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 30×30 m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。
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.
Estimate parameters and algorithm of a tree growthso 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 gridthen examine that distribution of vegetation and GPP at equilibrium are reasonably simulated.
Procedure for parameter estimation and tuning
(1)
(2)
(3)
(4)
(5)
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
Schedule
・ within Oct
・ 2 to 4 month
・ 1 to 3 month
・ ?