| Measuring annual growth pattern for tropical trees without distinct annual rings using oxygen isotopes |
| Paper ID : 1046-ADA2013 |
| Authors: |
|
CHENXI XU *1, Masaki Sano2, takeshi Nakatsuka3, Kei Yoshimura4 1Graduate school of Environmental Sciences,
(Room 424, Hydrospheric Atmospheric Research
Center), Nagoya University
Furo-Cho, Chikusa-ku, Nagoya 464-8601, Japan 2Graduate School of Environmental Studies, Nagoya University,
Furo-Cho, Chikusa-ku, Nagoya 464-8601, Japan 3Graduate School of Environment Studies, Nagoya University, 4Atmosphere and Ocean Research Institute, University of Tokyo |
| Abstract: |
| In this study, we measured radial variation of cellulose oxygen isotope in tree species that grow in seasonally dry forests of Northern Laos to explore the possibility to use radial variation of oxygen isotope for the identiļ¬cation of annual growth pattern for trees that lack visually detectable and consistent growth rings in tropical area. One disk is 7 years old Styrax in secondary forest which is used for shifting cultivation (slash-and-burn agriculture), so we get the age of Styrax from local villagers. In addition, two cores from two Ficus sp and one core from Shorea sp in natural forests were examined. Styrax and Shorea sp show non-distinct ring boundary, while Ficus sp has apparent rings. We measured Styrax and Shorea sp by 1 mm and 0.5 mm resolution, respectively. To test whether the apparent rings of Ficus sp are annual rings or not, we analyzed tree ring oxygen isotopes of two Ficus sp cores by apparent rings. Our results show that cellulose oxygen isotope ratios of Styrax and Ficus sp showed clear cyclic patterns with amplitude of 5‰ and 9‰, respectively. We assume that the formation of these oxygen isotope cycles is derived from annual cycle in local hydroclimate. The mean annual precipitation is 1458.8 mm at study area, 78% of which falls in the monsoon months from May to September. Relative humidity is higher in rainy season (from May to September) and is lower in dry season (from November to April). In rainy season, both lower precipitation δ18O due to heavy rainfall (amount effect) and higher relative humidity (weak evapotranspiration) result in lower tree ring cellulose δ18O, while tree ring cellulose δ18O is higher in dry season due to low relative humidity and high precipitation δ18O. To further test if oxygen isotope cycles that we observed are annual or not, tree ring cellulose oxygen isotope model is employed. Input data of the model are relative humidity and modeled precipitation δ18O. Modeling results independently supports our detection of oxygen isotopes annual cycles. Therefore, we concluded that tree ring cellulose oxygen isotope ratios have great potential to identify the annual growth pattern for tropical trees without distinct annual rings in the context of seasonal climate. |
| Keywords: |
| tree ring cellulose oxygen isotope, annual cycles, trees with non-distinct annual rings, Styrax, Ficus |
| Status : Abstract Accepted |
© 2010 - 2024 All Rights Reserved. Powered by sinaweb.