Hydraulic constraints on photosynthesis in subtropical evergreen broad leaf forest and pine woodland trees of the Florida Everglades |
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Authors: | Tim J Jones Corene D Luton Louis S Santiago Guillermo Goldstein |
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Institution: | 1. Agricultural Research Service, US Department of Agriculture, Reno, NV, 89512, USA 2. Nevada Fisheries Resource Office, US Fish and Wildlife Service, Reno, NV, 89502, USA 3. Botany and Plant Sciences, University of California, 2150 Batchelor Hall, Riverside, CA, 92521, USA 4. University of Miami, P.O. Box 249118, Coral Gables, FL, 33124, USA 5. Laboratorio de Ecología Funcional (CONICET), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II 2o piso, C1428EHA, Buenos Aires, Argentina
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Abstract: | The relationship between water transport and photosynthesis represents the trade-off between carbon gain and water loss and
was used to evaluate potential differences in water resource utilization among two dominant vegetation types of south Florida:
subtropical evergreen broad leaf forests (hardwood hammocks) and pine woodlands (pine rocklands). We found consistent linear
positive relationships between the quantum yield of photosystem II (ϕ
PSII), an index of photosynthetic capacity, and hydraulic conductivity per sapwood area (k
S) and per leaf area (k
L) across all species. The slope of the ϕ
PSII–k
S relationship was steeper for hardwood hammock than for pine rockland species. Mean ϕ
PSII was greater in pine rockland species and was greater for a given k
L than in hardwood hammock species. These results are consistent with previous observations demonstrating that pine rocklands
tend to have better access to stable water sources than hardwood hammocks. We also found greater photosynthetic carbon isotope
discrimination with increasing k
S and k
L in pine rockland species, but not in hardwood hammock species, suggesting increased stomatal conductance with increasing
k
S and k
L, consistent with greater water availability in pine rockland habitats. Our study thus utilizes relationships between water
transport and photosynthesis to evaluate hydraulic constraints on physiological function between two contrasting vegetation
types with contrasting stability of water sources. |
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