Size-dependent mortality in a Neotropical savanna tree: the role of height-related adjustments in hydraulic architecture and carbon allocation.
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 approximately 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 CO(2) 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.
Zhang
Yong-Jiang
YJ
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan, China.
Meinzer
Frederick C
FC
Hao
Guang-You
GY
Scholz
Fabian G
FG
Bucci
Sandra J
SJ
Takahashi
Frederico S C
FS
Villalobos-Vega
Randol
R
Giraldo
Juan P
JP
Cao
Kun-Fang
KF
Hoffmann
William A
WA
Goldstein
Guillermo
G
D001938:Brazil; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D007887:Fabaceae / Q000502:physiology*; D018515:Plant Leaves / Q000502:physiology*; D018547:Plant Stems / Q000502:physiology*; D054046:Plant Stomata / Q000502:physiology; D018526:Plant Transpiration / Q000502:physiology; D014197:Trees / Q000502:physiology; D014867:Water / Q000502:physiology*; D014934:Wood / Q000502:physiology
D014867:Water; D002245:Carbon Dioxide; D002244:Carbon