title: Contrasting seasonal leaf habits of canopy trees between tropical dry-deciduous and evergreen forests in Thailand.
abstract: We compared differences in leaf properties, leaf gas exchange and photochemical properties between drought-deciduous and evergreen trees in tropical dry forests, where soil nutrients differed but rainfall was similar. Three canopy trees (Shorea siamensis Miq., Xylia xylocarpa (Roxb.) W. Theob. and Vitex peduncularis Wall. ex Schauer) in a drought-deciduous forest and a canopy tree (Hopea ferrea Lanessan) in an evergreen forest were selected. Soil nutrient availability is lower in the evergreen forest than in the deciduous forest. Compared with the evergreen tree, the deciduous trees had shorter leaf life spans, lower leaf masses per area, higher leaf mass-based nitrogen (N) contents, higher leaf mass-based photosynthetic rates (mass-based P(n)), higher leaf N-based P(n), higher daily maximum stomatal conductance (g(s)) and wider conduits in wood xylem. Mass-based P(n) decreased from the wet to the dry season for all species. Following onset of the dry season, daily maximum g(s) and sensitivity of g(s) to leaf-to-air vapor pressure deficit remained relatively unchanged in the deciduous trees, whereas both properties decreased in the evergreen tree during the dry season. Photochemical capacity and non-photochemical quenching (NPQ) of photosystem II (PSII) also remained relatively unchanged in the deciduous trees even after the onset of the dry season. In contrast, photochemical capacity decreased and NPQ increased in the evergreen tree during the dry season, indicating that the leaves coped with prolonged drought by down-regulating PSII. Thus, the drought-avoidant deciduous species were characterized by high N allocation for leaf carbon assimilation, high water use and photoinhibition avoidance, whereas the drought-tolerant evergreen was characterized by low N allocation for leaf carbon assimilation, conservative water use and photoinhibition tolerance.
authors.affiliation: Department of Plant Ecology, Forestry and Forest Products Research Institute, Tsukuba, Ibaraki 305-8687, Japan. atto@ffpri.affrc.go.jp
authors.forename: Atsushi
authors.initials: A
authors.lastname: Ishida
authors.forename: Sapit
authors.initials: S
authors.lastname: Diloksumpun
authors.forename: Phanumard
authors.initials: P
authors.lastname: Ladpala
authors.forename: Duriya
authors.initials: D
authors.lastname: Staporn
authors.forename: Samreong
authors.initials: S
authors.lastname: Panuthai
authors.forename: Minoru
authors.initials: M
authors.lastname: Gamo
authors.forename: Kenichi
authors.initials: K
authors.lastname: Yazaki
authors.forename: Moriyoshi
authors.initials: M
authors.lastname: Ishizuka
authors.forename: Ladawan
authors.initials: L
authors.lastname: Puangchit
mesh_terms: D018533:Biomass; D002734:Chlorophyll / Q000378:metabolism; D032462:Cycadopsida / Q000378:metabolism / Q000502:physiology; D017753:Ecosystem; D019684:Magnoliopsida / Q000378:metabolism / Q000502:physiology; D010788:Photosynthesis / Q000502:physiology; D018515:Plant Leaves / Q000378:metabolism / Q000502:physiology*; D012621:Seasons; D013785:Thailand; D014197:Trees / Q000378:metabolism / Q000502:physiology*; D014329:Tropical Climate
chemical_list: D002734:Chlorophyll