Size-dependent mortality in a Neotropical savanna tree: the role of height-related adjustments in hydraulic architecture and carbon allocation |
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| Authors: | YONG-JIANG ZHANG FREDERICK C MEINZER GUANG-YOU HAO FABIAN G SCHOLZ SANDRA J BUCCI FREDERICO S C TAKAHASHI RANDOL VILLALOBOS-VEGA JUAN P GIRALDO KUN-FANG CAO WILLIAM A HOFFMANN & GUILLERMO GOLDSTEIN |
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| Institution: | Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China,;Department of Biology, University of Miami, PO Box 249118, Coral Gables, FL 33124, USA,;Graduate School of the Chinese Academy of Sciences, Beijing 100039, China,;USDA Forest Service, Forestry Sciences Laboratory, 3200 SW Jefferson Way, Corvallis, OR 97331, USA,;Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) and Laboratorio de Ecologia Funcional, Departamento de Biologia, Universidad Nacional de la Patagonia San Juan Bosco, Comodoro Rivadavia, Argentina,;Departamento de Ecologia, Universidade de Brasilia, Caixa Postal 04457, Brasilia, DF 70904970, Brazil,;Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA,;Department of Plant Biology, North Carolina State University, Raleigh, NC 27695-7612, USA and;Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) and Laboratorio de Ecología Funcional, Departamento de Ecologia, Genetica y Evolucion, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Nuñez, Buenos Aires, Argentina |
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| Abstract: | Size-related changes in hydraulic architecture, carbon allocation and gas exchange of Sclerolobium paniculatum (Leguminosae), a dominant tree species in Neotropical savannas of central Brazil (Cerrado), were investigated to assess their potential role in the dieback of tall individuals. Trees greater than ～6-m-tall exhibited more branch damage, larger numbers of dead individuals, higher wood density, greater leaf mass per area, lower leaf area to sapwood area ratio (LA/SA), lower stomatal conductance and lower net CO2 assimilation than small trees. Stem-specific hydraulic conductivity decreased, while leaf-specific hydraulic conductivity remained nearly constant, with increasing tree size because of lower LA/SA in larger trees. Leaves were substantially more vulnerable to embolism than stems. Large trees had lower maximum leaf hydraulic conductance ( K leaf) than small trees and all tree sizes exhibited lower K leaf at midday than at dawn. These size-related adjustments in hydraulic architecture and carbon allocation apparently incurred a large physiological cost: large trees received a lower return in carbon gain from their investment in stem and leaf biomass compared with small trees. Additionally, large trees may experience more severe water deficits in dry years due to lower capacity for buffering the effects of hydraulic path-length and soil water deficits. |
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| Keywords: | carbon balance hydraulic conductivity population dynamics tree dieback xylem cavitation |
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