1-1. Terrestrial carbon cycle model

a. Summary

It is the target of this subgroup to include in the earth system integrated model which builds the model which simulates the carbon cycle by a terrestrial ecosystem, and is built with this subject when building the earth environment change forecasting model by artificial greenhouse gas discharge, and to perform warming prediction.
The Heisei 17 fiscal year is (1). Reappearance of the carbon cycle during the 20th century by a terrestrial carbon cycle-climate joint model (Sim-CYCLE+MATSIRO+AGCM), and (2) It worked about two points of an advancement of the terrestrial carbon cycle model (Sim-CYCLE) by observational data.
As a result, (1) The developed joint model could express the carbon cycle in the 20th century well, and it was thought that the availability of a model was high.
(2) It was shown that technique development of the data assimilation which will have prediction nature in the future may be performed, and it may contribute to the improvement in presumed accuracy of a terrestrial model by the optimization using MODIS satellite observational data of parameter values.

b. Research purpose

the carbon balance of the present earth -- being artificial (fossil fuel expenditure, land use diversification, etc.) -- an abbreviation half remains in the atmosphere among the discharged carbon dioxide (they will be about 7 PgC(s)/a year at the 1980s), and the remaining half is absorbed by the ocean and terrestrial. The terrestrial ecosystem has played the role important for the carbon balance of the earth also from a global aspect. However, in the present carbon cycle research, the carbon balance of a terrestrial ecosystem has many unsolved problems, and is further considered to be one of the factors which enlarge uncertainty of prediction also in the future earth environment change prediction by greenhouse gas discharge. If some researches using an earth system integrated model are compared, future carbon dioxide levels and climate change prediction change greatly with between models (for example, Friedlingstein et al.2003), and the difference in the response of the carbon balance to earth environment change of a terrestrial ecosystem is considered to be one big factor.

This sub group's purpose is (1). The model which is highly precise and presumes a terrestrial ecosystem carbon cycle is built, and it is (2). It is including in the earth system integrated model built in this subject.

Although breathing by the photosynthesis and the plant by a plant, and edaphone is main as carbon balance between the atmosphere and terrestrial vegetation, in order to reproduce a long-term ecosystem, it is necessary to take into consideration the complicated various process in the inside of an ecosystem. It is rare to be solved about those physiological ecology character, and although derivation of a general model leaves an experiential portion from a difficult thing, it needs to aim at parameterization with few errors. Therefore, modeling is advanced, promoting the observation project and cooperation of symbiosis 3rd (terrestrial ecosystem) etc. If in charge of inclusion to an earth system integrated model, the more reliable simulation in consideration of the interaction of climate and a carbon cycle becomes possible by combining a terrestrial carbon cycle model to the present air-sea joint general circulation model (AOGCM). For example, if it may work in the direction which vegetation absorbs more CO₂ by extending the vegetation growing season in a cold district by warming, and eases CO₂ concentration rise, a soil organic matter decomposition rate accelerates by warming, and CO₂ concentration rise may be promoted. The simulation in consideration of the link of such climates and carbon cycles becomes possible.

c. A research program, a method, and a schedule

When building an earth system integrated model, each component fully needs to be verified. About verification of a model, it is (1). Ground observation group of symbiosis 3rd (terrestrial),Verification of a small acreage base which used the continuation observational data of the water, the heat, and carbon dioxide commutation between air-terrestrial by the flux group of the Ministry of Environment general investigation promotion expense S1 etc.,(2) Comparison of the satellite observational data (the absorptivity of LAI and photosynthetically active radiation and photosynthesis quantity of production of vegetation) of broad-based vegetation activities and a model estimated value by the satellite observation group of symbiosis 3rd (terrestrial) etc. is performed.

Off-line evaluation of a model is performed in parallel to verification of the above-mentioned model. The carbon balance in the past - the present global scale is reproduced, and change of the terrestrial carbon cycle under future carbon dioxide levels and climate change scenario conditions is simulated. The elucidation by an off-line simulation is advanced about the factor of the uncertainty of the future prediction in the present integrated model research using the climate scenario reproduced under various greenhouse gas discharge scenario conditions.

It is most efficiently attained by this group in terrestrial integrated model building by combining the model of the both sides of the Sim-CYCLE model (Ito and Oikawa, 2002) reproducing a carbon cycle, and the MATSIRO model (Takata et al., 2003) reproducing heat and a water cycle. About the interaction of air-terrestrial, MATSIRO calculates heat and water exchange, and a photosynthetic rate based on LAI by Sim-CYCLE. Based on the amount of photosynthesis by the MATSIRO, Sim-CYCLE calculates many process inside ecosystems, such as distribution to each part of vegetation, consumption by breathing or withering to death, and decomposition in soil. That is, it has a complementary relation of obtaining the net amount of exchange as the sum total because MATSIRO presumes the CO₂ absorption to terrestrial from the atmosphere and Sim-CYCLE presumes the CO₂ discharge from terrestrial.

Internationally, some trials to an integrated model exist besides this project. In order to perform more synthetic evaluation from the background, the international comparison project (Coupled Climate Carbon Cycle Model Intercomparison Project:C4MIP; both climate-carbon cycle joint model comparison project) of an earth system integrated model was shown in the Heisei 15 fiscal year. Now, the model simulation for comparison of each endowed institution is performed. This subject is also considered to be an indispensable condition when performing competition with international participating in this project, and a measure is advanced. The interaction of a terrestrial carbon cycle model and a general circulation model is to give CO₂ concentration in the 20th century, and land use change data as an input of a model, and to be evaluated as the first step, and the procedure document (protocol) of an experiment is also shown. This correspondence is performed.

As a next stage, extension for taking structural change of a terrestrial ecosystem into consideration is performed. The more nearly actually near prediction experiment in consideration of composition change of the vegetable types (an evergreen broad-leaved tree, a shrub, grassy place, etc.) which constitute an ecosystem from linking with the dynamic vegetation distributed model which the terrestrial dynamic state subgroup of this subject develops is conducted. It is made to converge on the integrative model about MATSIRO, Sim-CYCLE, and terrestrial that linked the vegetation dynamic model. The prediction experiment by the integrated model which finally introduced the influence which a water heat budget-carbon balance-vegetation change in structuretextural change has on a climate system is conducted.

d. The research program in the Heisei 17 fiscal year

This fiscal year is (1). Reappearance of the carbon cycle during the 20th century by the joint model of Sim-CYCLE+MATSIRO+AGCM, and (2) Two points of an advancement of Sim-CYCLE by observational data are performed. It is as follows for details.

By the last fiscal year, maintenance of the code of a climate-terrestrial carbon cycle joint model and parameter tuning were completed mostly. However, in order to carry out prediction in the future using this model, sufficient accuracy needs to be verified. Then, while reproducing the carbon cycle during the 20th century and verifying the validity of a model in the current fiscal year, detailed grasp of the carbon dynamic state in the 20th century was tried.

It is suggested to the simulation by a terrestrial ecosystem carbon cycle model from comparison verification with the mutual comparative experiments of a model, and observational data that big uncertainty is left behind. With the 3rd terrestrial subject of symbiosis, the data collection about a terrestrial ecosystem is performed through a satellite observation, field observation, and an experiment, and the advancement of the terrestrial ecosystem model (for example, carbon cycle model Sim-CYCLE currently used by the earth system integrated model of the 2nd subject of symbiosis) using the data has been a future material subject. Then, this year examines the technique of having used especially satellite data about the advancement of the physiology ecology parameter contained in a terrestrial ecosystem model, taking the 3rd terrestrial subject of symbiosis, and cooperation.

e. Fruits of work in the Heisei 17 fiscal year

A research program is followed and it is (1). Reappearance of the carbon cycle during the 20th century by the joint model of Sim-CYCLE+MATSIRO+AGCM, and (2) Two points of an advancement of Sim-CYCLE by observational data were performed. Details are shown below.

The relation between all the ball carbon dynamic states in the 20th century and the carbon burst size by land use change was investigated using the climate-terrestrial carbon cycle joint model (Sim-CYCLE-MATSIRO-AGCM) completed at the last fiscal year.

As Forcing data, the year by year variation of CO₂concentration was given to the sea skin temperature SST and atmospheric radiation process which were created in Britain Hadley Centre. Moreover, in our model, the carbon dynamic state change process (Houghton et al., 1983) by land use change was introduced, and the data of land use change created by the University of Wisconsin semiautomatic-ground-environment group was given as the input value. Although created by the spatial resolution of 0.5^o interpolation was carried out and this data was used so that the resolution of a model might be suited.

In order to create the stable initial value about a terrestrial carbon pool, the following procedures performed the spin nappe run. (1) Assign a very small value (0.001 Mg C/ha) to the carbon pool of each grid, and perform for 1000 years with a Sim-CYCLE simple substance. As climate data to input, by the joint model, the simulation result by 1875 to 1899 created beforehand was repeated 40 times, and was used. (2) Repetition calculation of the joint model was carried out 3 times about 25 years from 1875 to 1899 by making the created carbon pool data into an initial value. The initial value of the carbon pool stabilized in the integrated state on January 1, 1900 by this was created.

The net primary production (NPP) and heterotroph breathing (HR) which carried out all ball addition increased gradually in 100 years, and were increasing average of the 1990s from the thing of the 1900s (NPP:6.7% HR: 4.7%). (figure 1. above figure) . On the other hand, the ecosystem net production (NEP: NPP-HR) which is those totals is changed by the width of ±2.0 Pg C yr^-1, and it will see on the average in the first half of the 20th century, and although it was neutral, the about positive value will be shown the second half of the 20th century, and it is shown that the terrestrial ecosystem was the sink of the atmosphere CO ₂ (the figure 1. following figure black line). However, when the burst size (LUC_efflux) of the carbon by land use change was taken into consideration, it turned out that the net carbon absorbed amount of terrestrial often becomes negative (NEP-LUC_efflux; the figure 1. following figure red line). It turned out that especially this LUC_efflux is large in Southeast Asia or South America, and the influence reaches the total of all the balls for 100 years also at 44.4 Pg C, and affect the carbon cycle of all balls is very large.

Fig. 1: All ball carbon dynamic states in terrestrial ecosystem

Next, in order to investigate the cause of an increase of NPP and HR, the control experiment (SST-ctrl) which fixed only SST in 1900, and the control experiment (CO₂-ctrl) which fixed only CO₂ concentration in 1900 were conducted (Fig. 2). As a result, although the value of SST-ctrl showed a fiducial point (Normal) and near play about NPP, it was much less than CO₂-ctrl from Normal. From this, a possibility that the increase in NPP in the 20th century was brought about by the rise of the photosynthetic rate by the increase in CO₂ concentration rather than warming was suggested.

On the other hand, although the value increased HR by SST-ctrl to CO₂-ctrl having hardly changed like NPP, Normal and CO₂-ctrl of the degree were in-between. From this, as for the increase in HR in the 20th century, it was suggested by warming that two processes of activity of a microbial activity and the increase in respiratory substances, such as litter accompanying a NPP upsurge and the soil biomass, by the increase in CO₂ concentration are causality.

Fig. 2: Transition of (a) NPP and (b) HR in terrestrial ecosystem
(CO₂-ctrl: Normal: The control run which fixed only Fig. 1 above figure, and equivalent and SST-ctrl: SST in 1900, and control run which fixed only CO₂ concentration in 1900)

Fig. 3: Change of air CO₂ concentration. What hung 0.25 and 0.75 and added the observed value of the South Pole and Mauna Loa is used for an observed value (Observation).

Table 1: All average ball carbon balance in the 1980s (unit: Pg C yr^-1).

	This research	McGuire et al. (2001)	Houghton (2003)
Discharge by a fossil fuel *	5.4		5.4 ± 0.3
Absorption by the ocean. * †	-2.2		- 1.7 ± 0.6
Absorption by terrestrial † * The divided value (below two lines)	-0.1	- 1.5 to -0.3	- 0.4 ± 0.7
Discharge accompanying land use change (LUCefflux)	0.5	0.6 to -1.0	2.0 ± 0.8
Absorption by a terrestrial ecosystem † (-NEP)	-0.6	- 2.3 to -1.1	- 2.4 ± 1.1
Increment of air CO2 concentration	3.3		3.3 ± 0.1

* Use the data prepared beforehand in this research. A † negative value shows "absorption."

The 3rd subject "research on parameterization for terrestrial ecosystem model creation" of symbiosis serves as participation organizations with Manufacturing Engineering Research Center, the University of Tokyo, (representation: Yoshifumi Yasuoka) which is a generalization organization, and main Hokkaido University and Forestry and Forest Products Research Institute. The main purpose of this project is attaining highly precise-ization of parameterization which acquires the various observational data about the carbon cycle of a terrestrial ecosystem, and is contained in model Sim-CYCLE (Ito and Oikawa, 2002) using it. In order to leave behind big uncertainty to presumption and prediction by the present terrestrial ecosystem model and to raise the reliability of the future warming prediction using an earth system integrated model, there is a situation that it is indispensable to reduce the uncertainty in the background that establishment of such a subject is needed. It participated in the steering committee of the 3rd terrestrial subject of symbiosis on June 30, 2005, and the scheme and conditions of material 4 subject matters which are performed with this subject have been grasped.

• terrestrial vegetation monitoring in the broader-based scale by satellite remote sensing: The algorism development about the observation of the leaf area index (LAI) in global terrestrial vegetation or a photosynthetically-active-radiation absorptivity (fAPAR) by MODIS etc., verification, and the investigation on exploitation by a model are done by Manufacturing Engineering Research Center, the University of Tokyo, and Forestry and Forest Products Research Institute.
  
  
• The observation of the reaction which the fire in an East Siberia larch wood has on carbon balance:
  In the Yakutsk suburbs in East Siberia, enquiry of the flux observation of CO₂ income and expenditure for a larch wood, soil respiration, etc. is conducted. It is focused on the reaction which a forest fire has on carbon balance, and the phenomenon elucidation with diversification of the hot water income and expenditure after a fire peculiar to an area, such as causing dissolution of a permafrost layer, is offered there.
  
  
• the Sapporo sheep hill observation of CO₂flux in a site, and a carbon cycle element
  In the cool-temperate-zone deciduous broad-leaved forest of the close of Forestry and Forest Products Research Institute of Sapporo sheep Oka, enquiry of CO₂ flux observation and soil respiration by eddy correlation, an individual leaf quality, etc. is conducted. Although this site suffered damage with serious forest and observation tower from the typhoon in autumn of 2004, observation equipment is rebuilt and observation about change of the carbon balance in the recovery process after forest collapse is performed.
  
  
• The vegetable exposure experiment to high CO₂ concentration in the enclosure of Hokkaido University
  Most researches for trees were not done about the influence which future high CO₂ concentration environment has on a vegetable physiology process and a vegetable dynamic state. In this research, the experiment which grows sapling in a high CO₂ concentration environment using a Free-Air CO₂ Enrichment (FACE) system is conducted, and examination is performed about the difference in the grade of the fertilizing effect by the difference of nutrition conditions etc.

Some methods, such as an input, proofreading, and verification, are one of the methods of using observational data in a model. With the symbiosis 3-terrestrial subject, the advancement of parameterization is aimed at and development to not only re-proofreading but verification of parameter values and the successive parameter correction finally according to data assimilation which are used by the existing model, and a prediction system is also put into the view. The advancement of photosynthesis quantity-of-production presumption by the "nazzing" method using LAI and fAPAR data of all ball scales based on MODIS was actually carried out by the last fiscal year (Hazarika et al., 2005). Moreover, the observational data in East Siberia is used by the fire style-carbon cycle joint model (Ito, 2005) of a scene scale.

On the other hand, by the "nazzing" method, since compensation of parameter values is not performed, the improvement in accuracy to prediction cannot be expected in the future. Therefore, although LAI and fAPAR by MODIS were similarly used in the current fiscal year, technique development of data assimilation with the future prediction nature by optimization of parameter values was tried (joint research with Manufacturing Engineering Research Center, the University of Tokyo). The specific leaf area (SLA, Specific Leaf Area) which is the form parameter of individual leaf was made into the object parameter after the examination about the availability of data, or the importance in the inside of a model. SLA of the terrestrial model currently used by the conventional earth system model etc. is a constant for every vegetation type, and neither a seasonal variation nor space change is taken into consideration. On the other hand, SLA is considered to be the important parameter which connects the carbon weight and surface area of a leaf. Here, the SLA value was optimized so that LAI by satellite observation might be connected with the leaf weight presumed by the carbon balance formula from the model. As a result, it was shown that that space change within a vegetation type remarkable in SLA and a seasonal variation have arisen may contribute SLA which was suggested and was obtained here to the improvement in accuracy of a model simulation by using for prediction in the future.

f. Consideration

In order to verify the presumed possibility of a joint model in the current fiscal year, it has gone focusing on reappearance of the carbon cycle in the 20th century. As a result, the developed joint model could express the carbon cycle in the 20th century well, and it was thought that the availability of a model was high. The following fiscal year is due to perform improvement for taking in the function of vegetation change while conducting a prediction experiment in the future using this joint model. Specifically, dynamic vegetation distributed model SEIB-DGVM which prediction of the climate-carbon dynamic state interaction change during the 21st century using a Sim-CYCLE-MATSIRO-AGCM joint model and the terrestrial dynamic state subgroup of this subject develop is due to be introduced.

The data assimilation by a terrestrial ecosystem model is one of the latest important themes, and the project which called CCDAS (Carbon Cycle Data Assimilation System) in CarboEuro already performed in Europe, and was called LDAS (Land Data Assimilation System) and EcoCast in the U.S. is advancing. The observational data of air CO₂ concentration is going to be acquired at ground data, such as flux observation, the broader-based data based on satellite observation, and the time, and each is going to be collected there to the advancement of a terrestrial model. Having started the same trial in the symbiosis 3-terrestrial subject can be regarded as very important progress in such a flow. The advancement in a model using acquisition data other than satellite observation (example: flux observation, ecosystem investigation, FACE experiment) is started from now on, and it is thought important to accelerate reduction of the uncertainty of a terrestrial model further.

g. Bibliography

h. The announcement of a result