HR: 0830h
AN: B51E-1013    [PDF]
TI: Recent climate-induced variations in terrestrial carbon cycle over tropics: A model simulation
AU: * Ichii, K
EM: ichii@eps.nagoya-u.ac.jp
AF: Nagoya Univeristy, Furo-cho, Chikusa, Nagoya, 464-8601 Japan
AU: Nemani, R R
EM: nemani@ntsg.umt.edu
AF: NASA Ames Research Center, Moffett Field, Sanjose, CA 94035 United States
AU: Hashimoto, H
EM: hiro@ntsg.umt.edu
AF: NASA Ames Research Center, Moffett Field, Sanjose, CA 94035 United States
AB: Tropical forests accounts for about 20 percent of the world terrestrial carbon and one-third of global terrestrial NPP. Atmospheric inversion studies show that additional factors such as CO2 fertilization and climate changes, should work as a carbon sink despite of CO2 emission due to deforestation in tropical regions. However, responses of tropical ecosystems to environmental changes and current carbon sink mechanisms are still unknown. The goal of this study is (1) to characterize the climate influences on tropical carbon cycle such as GPP, NPP and NEP, and (2) to analyze recent interannual variations in terrestrial carbon cycle over tropics. We investigated the relationship between climate factors (temperature, precipitation, radiation, and VPD) and several carbon cycle components, and analyzed recent carbon cycle variations over tropics using Biome BGC with NCEP reanalysis climate data from 1982 to 1999. In tropical ecosystems, interannual variations in GPP are mainly explained by radiation variations, and temperature and precipitation variation are secondary important. NPP and NEP interannual variations are primarily determined by temperature variation, and radiation came as a secondary important factors. Precipitation, which was considered as an important climate factor that control interannual variations in carbon cycle in tropics, has little effects on interannual variation in tropical carbon cycle possibly because of abundant rainfall. Then, recent interannual variations in terrestrial carbon cycle over tropics were analyzed from 1982-1999. Tropics show gradual increases in GPP, NPP, and NEP at a rate of several percent per recent 18 years with large drop in 1998. Both climate change and CO2 fertilization have impact on recent enhancement of terrestrial carbon uptake. Of all climate factors, radiation-induced enhancement shows important role in enhancing CO2 uptake over Amazon. On the other hand, variations in precipitation and vapor pressure did not make any trend. We compared NCEP radiation data with other independent observations, and concluded that radiation-induced enhancement of terrestrial carbon uptake is certain.
DE: 0400 Biogeosciences
DE: 1600 GLOBAL CHANGE (New category)
DE: 1615 Biogeochemical processes (4805)
DE: 1640 Remote sensing
SC: Biogeosciences [B]
MN: 2003 Fall Meeting