Keywords :
Dipterocarpaceae,
Seasonally dry forest,
Stable carbon isotope,
Tropical dendrochronology,
Wood anatomy
บทคัดย่อ :
We measured radial variation of carbon isotope
composition and vessel traits in tree species in seasonally
dry forests of Northeast Thailand to explore a more reliable
and amenable method of tropical dendrochronology for
trees that lack visually detectable and consistent growth
rings. Six Dipterocarpaceae species (3 Shorea, 2 Diptero-
carpus, and 1 Hopea species) with indistinct or irregular
growth rings and teak (Tectona grandis), a species which
forms distinct growth rings, were examined. The d13C
value variations in all species showed annual cyclicity.
Dipterocarpaceae species usually marked the lowest values
of d13C in the middle of the growing season, whereas teak
had the lowest values at nearly the end of the growing
season. Since the growing season of the species examined
almost corresponds to the rainy season in the study area,
the d13C variation was likely caused by the change in
moisture availability. The different variation pattern of teak
was attributable to its stronger dependence on 13C-enriched
reserved material early in the growing season. Changes in
tree vessel traits for all species examined also showed
annual cyclicity. Dipterocarpaceae species showed sig-
nificant correlation between d13C values and vessel
measurements. Vessel lumen (mean area, tangential and
radial diameter, and proportion of total area) had a negative
correlation, whereas vessel frequency showed a positive
correlation. The correlations indicated that changes in
vessel traits were caused by the seasonal variation of
moisture available to the trees. Thus, we concluded that
methods using wood anatomy, as well as d13C, have great
potential for use as tools in tropical dendrochronology
within the context of seasonal climate.
เอกสารอ้างอิง :
Ohashi, S., Okada, N., Nobuchi, T., Siripatanadilok, S., & Veenin, T. (2009). Detecting invisible growth rings of trees in seasonally dry forests in Thailand: isotopic and wood anatomical approaches. Trees, 23(4), 813-822.
