Development pressure has led to serious deforestation on the Indochina Peninsula. Particularly rapid defor-estation has occurred in easily accessible lowland areas, and it is thus important to accumulate knowledge about these forests immediately. We measured evapotranspiration rates for a lowland dry evergreen forest in Kampong Thom Province, central Cambodia, using the energy balance Bowen ratio (EBBR) method based on meteorological data collected from a 60-m-high observation tower. Daily evapotranspiration was higher during the dry season than during the rainy season of the Asian monsoon climate. The seasonal variation in evapotranspiration generally corresponded to the seasonal difference in the vapor pressure deficit. A multi-layer model was used to simulate the seasonal variation in evapotranspiration. The multilayer model also reproduced the larger evapotranspiration rate in the dry season than in the rainy season. However, observed values substantially exceeded model-calculated results during certain periods at the beginning of the dry season and in the late dry season. Moreover, during the rainy season, the model tended to overestimate evapotranspiration. The differences between these observed and simulated values may have been caused by seasonal characteristics of photosynthesis and transpiration in the lowland dry evergreen forest that were not considered in the model simulation.
KeywordsCambodiaEnergy Balance Bowen Ratio MethodEvapotranspirationLowland Dry Evergreen ForestMultilayered Model
A. Nalampoon, “National forest policy review, Thai-land,” in P. B. Durst Ed., “An overview of forest policies in Asia,” FAO, Bangkok, pp. 293–311, 2003.
E. Savet and T. Sokhun, “National forest policy review, Cambodia,” in P. B. Durst Ed., “An overview of forest policies in Asia,” FAO, Bangkok, pp. 93–108, 2003.
B. Krishnapillay, “Silviculture and management of teak plantations,” Unasylva, Vol. 201, pp. 14–21, 2000.
A. Mittelman, “Teak planting by smallholders in Nakhon Sawan, Thailand,” Unasylva, Vol. 201, pp. 62–65, 2000.
R. T. Pinker, O. E. Thompson, and T. F. Eck, “The en-ergy balance of a tropical evergreen forest,” Journal of Applied Meteorology, Vol. 19, pp. 1341–1350, 1980.
P. Attarod, M. Aoki, D. Komori, T. Ishida, K. Fukumura, S. Boonyawat, P. Tongdeenok, M. Yokoya, S. Punkngum, and T. Pakoktom, “Estimation of crop coefficients and evapotranspiration by meteorological parameters in a rain-fed paddy rice field, cassava and teak plantations in Thailand,” Journal of Agricultural Meteorology, Vol. 62, pp. 93–102, 2006.
K. Tanaka, H. Takizawa, N. Tanaka, I. Kosaka, N. Yo-shifuji, C. Tantasirin, S. Piman, M. Suzuki, and N. Tang-tham, “Transpiration peak over a hill evergreen forest in northern Thailand in the late dry season: Assessing the seasonal changes in evapotranspiration using a multilayer model,” Journal of Geophysical Research, Vol. 108 (D17), pp. 4533, 2003.
T. Kume, H. Takizawa, N. Yoshifuji, K. Tanaka, C. Tan-tasirin, N. Tanaka, and M. Suzuki, “Impact of soil drou- ght on sap flow and water status of evergreen trees in a tropical monsoon forest in northern Thailand,” Forest Ecology and Management, Vol. 238, pp. 220–230, 2007.
K. Tanaka, H. Takizawa, T. Kume, J. Xu, C. Tantasirin, and M. Suzuki, “Impact of rooting depth and soil hydrau-lic properties on the transpiration peak of an evergreen forest in northern Thailand in the late dry season,” Jour-nal of Geophysical Research, Vol. 109, D23107, 2004.
N. Tanaka, T. Kume, N. Yoshifuji, K. Tanaka, H. Taki-zawa, K. Shiraki, C. Tantasirin, N. Tangtham, and M. Suzuki, “A review of evapotranspiration estimates from tropical forests in Thailand and adjacent regions,” Agri-cultural and Forest Meteorology, Vol. 148, pp. 807–819, 2008.
Y. Ohnuki, C. Kimhean, Y. Shinomiya, and J. Toriyama, “Distribution and characteristics of soil thickness and ef-fects upon water storage in forested areas of Cambodia,” Hydrological Processes, Vol. 22, pp. 1272–1280, 2008.
N. Kabeya, A. Shimizu, T, Nobuhiro, and K. Tamai, “Preliminary study of flow regimes and stream water residence times in multi-scale forested watersheds of central Cambodia,” Paddy and Water Environment, Vol. 6, pp. 25–35, 2008.
A. Shimizu, N. Kabeya, T. Nobuhiro, T. Kubota, Y. Tsuboyama, E. Ito, M. Sano, S. Chann, and N. Keth, “Runoff characteristics and observations on evapotran-spiration in forest watersheds, central Cambodia,” in H. Sawada et al. Ed., “Forest Environments in the Mekong River Basins,” Springer, Tokyo, pp. 135–146, 2007.
J. Toriyama, S. Ohta, M. Araki, M. Kanzaki, S. Khorn, P. Pith, S. Lim, and S. Pol, “Soils under different forest types in the dry evergreen forest zone of Cambodia: Mor-phology, physicochemical properties, and classification,” in H. Sawada et al. Ed., Forest Environments in the Me-kong River Basins,” Springer, Tokyo, pp. 241–253, 2007.
Y. Ohnuki, C. Kimhean, Y. Shinomiya, S. Sor, J. Tori-yama, and S. Ohta, “Apparent change in soil depth and soil hardness in forest areas in Kampong Thom province, Cambodia,” in H. Sawada et al. Ed., “Forest Environ-ments in the Mekong River Basins,” Springer, Tokyo, pp. 263–272, 2007.
A. Shimizu, T. Shimizu, Y. Miyabuchi, and Y. Ogawa, “Evapotranspiration and runoff in a forested watershed, western Japan,” Hydrological Processes, Vol. 17, pp. 3125–3139, 2003.
S. Hattori, “Explanation on derivation process of equa-tions to estimate evapotranspiration and problems on the application to forest stand,” Bulletin of the Forestry and Forest Products Research Institute, Japan, Vol. 332, pp. 139–165, 1985.
J. C. Kaimal and J. J. Finnigan, “Atmospheric boundary layer flows: Their structure and measurement,” Oxford University Press, New York, 1994.
W. Brutsaert, Ed., “Evaporation into the atmosphere: theory, history, and applications,” D. Reidel Publishing Company, 1982.
K. Tamai, T. Nobuhiro, A. Shimizu, N. Kabeya, S. Chann, and K. Nang, “Characteristics of atmospheric stability above an evergreen forest in central Cambodia,” Hydro-logical Processes, Vol. 22, pp. 1267–1271, 2008.
G. D. Farquhar, S. V. Caemmerer, and J. A. Berry, “A biochemical model of photosynthetic CO2 assimilation in leaves of C3 species,” Planta, Vol. 149, pp. 78–90, 1980.
J. T. Ball, “An analysis of stomatal conductance,” Ph.D thesis, Stanford University, Stanford, California, 1988.
T. Watanabe, “The bulk transfer coefficients over a vegetated surface based on K-theory and 2nd-order clo-sure model,” Journal of the Meteorological Society of Japan, Vol. 71, pp. 33–42, 1993.
N. R. Wilson and E. H. Shaw, “A higher order closure model for canopy flow,” Journal of Applied Meteorology, Vol. 16, pp. 1197–1205, 1977.
K. Tanaka, “Multi-layer model of CO2 exchange in a plant community coupled with the water budged of leaf surfaces,” Ecological Modelling, Vol. 147, pp. 85–104, 2002.
K. Tanaka, Y. Kosugi, N. Ohte, S. Kobashi, and A. Na-kamura, “Model of CO2 flux between a plant community and the atmosphere, and simulation of CO2 flux over a planted forest,” (in Japanese with an English abstract) Japanese Journal of Ecology, Vol. 48, pp. 265–286, 1998.
J. Ross, “Radiative transfer in plant communities,” in J. L. Monteith Ed., “Vegetation and the atmosphere,” Vol. 1, Academic Press, California, pp. 13–55, 1975.
M. Araki, J. Toriyama, S. Ohta, M. Kanzaki, E. Ito, B. Tith, S. Pol, S. Lim, S. Khorn, P. Pith, and S. Det, “Soil moisture conditions in four types of forests in Kampong Thom, Cambodia,” in H. Sawada et al. Ed., “Forest envi-ronments in the Mekong river basins,” Springer, Tokyo, pp. 254–262, 2007.
M. Araki, A. Shimizu, J. Toriyama, E. Ito, N. Kabeya, T. Nobuhiro, B. Tith, S. Pol, S. Lim, S. Khorn, P. Pith, S. Det, S. Ohta, and M. Kanzaki, “Changes of vertical soil moisture conditions of a dry evergreen forest in Kampong Thom, Cambodia,” in H. Sawada et al. Ed., “Forest envi-ronments in the Mekong river basins,” Springer, Tokyo, pp. 112–124, 2007.
N. Kabeya, A. Shimizu, S. Chann, Y. Tsuboyama, T. Nobuhiro, N. Keth, and K. Tamai, “Stable isotope studies of rainfall and stream water in forest watersheds in Kampong Thom, Cambodia,” in H. Sawada et al. Ed., “Forest environments in the Mekong river basins,” Springer, Tokyo, pp. 125–134, 2007.
J. Matsumoto, “Seasonal transition of summer rainy sea-son over Indochina and adjacent monsoon region,” Ad-vances in Atmospheric Sciences, Vol. 14, pp. 231–245, 1997.
J. B. Stewart, “Modelling surface conductance of pine forest,” Agricultural and Forest Meteorology, Vol. 43, pp. 19–35, 1988.
K. G. McNaughton and P. G. Jarvis, “Predicting effects of vegetation changes on transpiration and evaporation,” in T. T. Kozlowski Ed., “Water deficits and plant growth,” Academic Press, New York, Vol. 7, pp. 1–47, 1983.
D. S. Ellsworth, “Seasonal CO2 assimilation and stomatal limitations in a Pinus taeda canopy,” Tree Physiology, Vol. 20, pp. 435–445, 2000.
S. Mediavilla and A. Escudero, “Photosynthetic capacity, integrated over the lifetime of a leaf, is predicted to be independent of leaf longevity in some tree species,” New Phytologist, Vol. 159, pp. 203–211, 2003.
Q. Han, T. Kawasaki, T. Nakano, and Y. Chiba, “Spatial and seasonal variability of temperature responses of bio-chemical photosynthesis parameters and leaf nitrogen content within a Pinus densiflora crown,” Tree Physiol-ogy, Vol. 24, pp. 737–744, 2004.
K. Kitajima, S. S. Mulkey, and S. J. Wright, “Seasonal leaf phenotypes in the canopy of a tropical dry forest: Photosynthetic characteristics and associated traits,” Oecologia, Vol. 109, pp. 490–498, 1997.
K. Kitajima, S. S. Mulkey, and S. J. Wright, “Decline of photosynthetic capacity with leaf age in relation to leaf longevities for five tropical canopy tree species,” Ameri-can Journal of Botany, Vol. 84, pp. 702–708, 1997.
F. C. Meinzer, G. Golostein, N. M. Holbrook, P. Jackson, and J. Cavelier, “Stomatal and environmental control of transpiration in a lowland tropical forest tree,” Plant, Cell and Environment, Vol. 16, pp. 429–436, 1993.
P. B. Reich, “Phenology of tropical forests: Patterns, causes, and consequences,” Canadian Journal of Botany, Vol. 73, pp. 164–174, 1994.
J. I. Pitman, “Ecophysiology of tropical dry evergreen forest, Thailand: measured and modelled stomatal con-ductance of Hopea ferrea, a dominant canopy emergent,” Journal of Applied Ecology, Vol. 33, pp. 1366–1378, 1996.
D. S. Thomas, D. Eamus, and S. Shanahan, “Influence of season, drought and xylem ABA on stomatal responses to leaf-to-air vapour pressure difference of trees of the Aus-tralian wet-dry tropics,” Australian Journal of Botany, Vol. 48, pp. 143–151, 2000.
K. Kitajima, S. S. Mulkey, M. Samaniego, and S. J. Wright, “Decline of photosynthetic capacity with leaf age and position in two tropical pioneer tree species,” American Journal of Botany, Vol. 89, pp. 1925–1932, 2002.