HR: 1340h
AN: B33D-1577    [Abstracts]
TI: Inter-annual Variation in Growing Season Length of a Tropical Seasonal Forest in Northern Thailand
AU: * Yoshifuji, N
EM: natsuko@fr.a.u-tokyo.ac.jp
AF: The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-8657, Japan
AU: * Yoshifuji, N
EM: natsuko@fr.a.u-tokyo.ac.jp
AF: Japan Science and Technology Agency, Honcho 4-1-8, Kawaguchi-shi, Saitama, 332-0012, Japan
AU: Tanaka, N
EM: tanaka@uf.a.u-tokyo.ac.jp
AF: The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-8657, Japan
AU: Suzuki, M
EM: suzuki@fr.a.u-tokyo.ac.jp
AF: The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-8657, Japan
AU: Tantasirin, C
EM: fforcct@ku.ac.th
AF: Kasetsart University, 50 Phahonyothin Road, Chatuchak, Bangkok, 10903, Thailand
AB: Growing season length is an important factor affecting energy balance and water and carbon cycling at deciduous forests. The impact of its inter-annual variation on annual energy and carbon exchange is likely to be critical especially in tropical region because of high radiant energy throughout the year; however, few studies investigated inter-annual variation in growing season length of tropical deciduous forests. This study revealed year-to-year variations in the canopy duration and transpiration period as measures of growing season length using time series data of radiative transmittance and heat pulse velocities of canopy trees in a teak plantation in northern Thailand from 2001 to 2006. This study also examined whether year-to-year variation in growing season revealed by field measurements could be detected by satellite NDVI data, as a first step to investigate the inter- annual variation in growing season length of deciduous forests over tropical monsoon region. Leaf-out and transpiration commenced earlier in 2001 than other years following exceptionally heavy rainfall in the late dry season, suggesting that enhanced soil moisture advanced leaf unfolding and start of transpiration. Leaf-fall and decline in transpiration at the beginning of 2003 were late in coming in correlation with a prolonged rainy season. Declines in transpiration were directly controlled by soil moisture at the beginning of the dry season. These results revealed that soil moisture is a major cause of large inter-annual variation in the growing season at this site. Seasonal variation in NDVI corresponded to that of LAI, while transpiration declined earlier than LAI and NDVI in the dry season. Year-to-year variation in canopy duration could be also detected by NDVI. The variation in canopy duration and transpiration period of this site from 2001-2006 spanned about 60 days. This was much larger than the inter-annual variations previously reported in temperate deciduous forests, implying a profound potential impact on energy, water, and carbon exchange on an annual time scale.
DE: 0476 Plant ecology (1851)
DE: 0480 Remote sensing
DE: 1807 Climate impacts
DE: 1813 Eco-hydrology
DE: 1818 Evapotranspiration
SC: Biogeosciences [B]
MN: 2007 Fall Meeting