Remote Sensing Satellite Observation of CO2 Exchange between the Arctic Terrestrial Ecosystem and the Atmosphere

Remote Sensing Satellite Observation of CO₂ Exchange between the Arctic Terrestrial Ecosystem and the Atmosphere

Dr. Tanaka and his colleagues will introduce the observational research activity for the effect of forests in the Arctic region to the global carbon budget.

Noriyuki Tanaka(Group Leader, International Arctic Research Center, FORSGC)
Yongwon Kim(Researcher, International Arctic Research Center, FORSGC)
Keiji Kushida(Assistant Professor, Institute of Low Temperature Science, Hokkaido University)

T he arctic region has a unique terrestrial ecosystem in the cold environment. In this ecosystem, temperature is a primary growth-limiting factor and the precipitation is the second one. It is very easy to say that the ecosystem could play an important role in the global carbon cycle, although it is unclear how the ecosystem responds to the coming global warming and climate change.

Remote sensing satellite observation has capability to retrieve vegetation type, Leaf Area Index (LAI), a good photosynthesis indicator, and soil temperature with relatively high precisions. As a result, the amount which vegetation assimilates atmospheric CO₂, so-called Gross Primary Production (GPP) and Net Primary Production (NPP), which is the difference between GPP and the amount that the vegetation respires, can be easily obtained using the satellite observation. However, we cannot know whether the vegetation is a sink or a source for the atmospheric CO₂ with NPP. Net Ecosystem Production (NEP) should be estimated by subtracting the soil respiration from NPP. We have simulated the soil respiration based on the satellite data (e.g., soil temperature and LAI) and the field-measured soil respiration in the vegetation. Specially, we have concentrated on the quantification and the factors affecting the emissions of greenhouse gases in thicker moss and lichen carpets on taiga and sub-alpine tundra of Arctic. The moss and lichen have significant roles on the cycles of greenhouse gases in the arctic terrestrial ecosystem (Kim and Tanaka, 2003).

We have carried out the intensive observation in moss and lichen mats on taiga and tundra (Fig. 1 a and b). Because the field-measurements are limited, we need to develop the process model of the soil respiration for the understanding of spacial and temporal variations. Recently, we try to apply to the arctic terrestrial ecosystem by tuning the field data to BIOME-BGC model (Kimball et al., 1997).

Fig.1

Moss and lichen carpets on taiga and tundra in artic ecosystem.

Figure 2 and 3 represent the distribution of the dominant vegetation, and NEP map obtained by applying the model in Caribou-Poker Creek Research Watershed (CRCPW), located 50 km north of Fairbanks, central Alaska during the growing season of 2000, respectively (Kushida et al., 2001). As the map has lots of vegetation classification, the analysis of the map is expected to clarify how the Arctic terrestrial ecosystems respond to the climate and the meteorological changes.


Fig.2 Distribution of the vegetations in central Alaska during the growing season.	Fig.3 NEP mapping (gC/m² /yr) in central Alaska during the growing season of 2000.

References
Kim, Y., and Tanaka, N., 2003: Effect of forest fire on the flux-es of CO₂, CH 4 , and N 2O in boreal forest soils, interior Alaska, Journal of Geophysical Research, 107 (D3), 8154, doi; 10. 1029/2001 JD000663.

Kimball, J. S., M. A. White, and S. W. Running, 1997: BIOME-BGC simulations of stand hydrologic processes for BORE-AS, Journal of Geophysical Research, 102 (D24), 29043- 29051.

Kushida, K., Y. Kim, Kojima, D., Shibuya, M., Tsuda, S., and Fukuda, M., 2001: Spectral decomposition of tundra vege-tation in Alaska for its spatial decomposition, Proceedings of the Second International Workshop in Global Change: Connection to the Arctic, 46-51.