title: Transpiration characteristics of a rubber plantation in central Cambodia.
abstract: The rapid and widespread expansion of rubber plantations in Southeast Asia necessitates a greater understanding of tree physiology and the impacts of water consumption on local hydrology. Sap flow measurements were used to study the intra- and inter-annual variations in transpiration rate (Et) in a rubber stand in the low-elevation plain of central Cambodia. Mean stand sap flux density (JS) indicates that rubber trees actively transpire in the rainy season, but become inactive in the dry season. A sharp, brief drop in JS occurred simultaneously with leaf shedding in the middle of the dry season in January. Although the annual maxima of JS were approximately the same in the two study years, the maximum daily stand Et of ∼2.0 mm day(-1) in 2010 increased to ∼2.4 mm day(-1) in 2011. Canopy-level stomatal response was well explained by changes in solar radiation, vapor pressure deficit, soil moisture availability, leaf area, and stem diameter. Rubber trees had a relatively small potential to transpire at the beginning of the study period, compared with average diffuse-porous species. After 2 years of growth in stem diameter, transpiration potential was comparable to other species. The sensitivity of canopy conductance (gc) to atmospheric drought indicates isohydric behavior of rubber trees. Modeling also predicted a relatively small sensitivity of gc to the soil moisture deficit and a rapid decrease in gc under extreme drought conditions. However, annual observations suggest the possibility of a change in leaf characteristics with tree maturity and/or initiation of latex tapping. The estimated annual stand Et was 469 mm year(-1) in 2010, increasing to 658 mm year(-1) in 2011. Diagnostic analysis using the derived gc model showed that inter-annual change in stand Et in the rapidly growing young rubber stand was determined mainly by tree growth rate, not by differences in air and soil variables in the surrounding environment. Future research should focus on the potentially broad applicability of the relationship between Et and tree size as well as environmental factors at stands different in terms of clonal type and age.
authors.affiliation: Hydrospheric Atmospheric Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan.
authors.forename: Nakako
authors.initials: N
authors.lastname: Kobayashi
authors.forename: Tomo'omi
authors.initials: T
authors.lastname: Kumagai
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Miyazawa
authors.forename: Kazuho
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Makiko
authors.initials: M
authors.lastname: Tateishi
authors.forename: Tiva K
authors.initials: TK
authors.lastname: Lim
authors.forename: Ryan G
authors.initials: RG
authors.lastname: Mudd
authors.forename: Alan D
authors.initials: AD
authors.lastname: Ziegler
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Giambelluca
authors.forename: Song
authors.initials: S
authors.lastname: Yin
mesh_terms: D002160:Cambodia; D008685:Meteorological Concepts; D008954:Models, Biological; D053147:Plant Exudates / Q000502:physiology; D018515:Plant Leaves / Q000502:physiology; D018547:Plant Stems / Q000502:physiology; D018526:Plant Transpiration / Q000502:physiology*; D012408:Rubber / Q000378:metabolism*; D012621:Seasons; D014197:Trees / Q000502:physiology
chemical_list: D053147:Plant Exudates; D012408:Rubber
keywords: Hevea brasiliensis; canopy conductance; canopy transpiration; environmental control; sap flow