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Co2 efflux, co2 concentration and photosynthetic refixation in stems of Eucalyptus globulus (Labill.)
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Orientador(es)
Resumo(s)
In spite of the importance of respiration in forest carbon budgets, the mechanisms by which physiological factors
control stem respiration are unclear. An experiment was set up in a Eucalyptus globulus plantation in central
Portugal with monoculture stands of 5-year-old and 10-year-old trees. CO2 efflux from stems under shaded and
unshaded conditions, as well as the concentration of CO2 dissolved in sap [CO2 *], stem temperature, and sap flow
were measured with the objective of improving our understanding of the factors controlling CO2 release from stems
of E. globulus. CO2 efflux was consistently higher in 5-year-old, compared with 10-year-old, stems, averaging 3.4
versus 1.3 mmol m22 s21, respectively. Temperature and [CO2 *] both had important, and similar, influences on the
rate of CO2 efflux from the stems, but neither explained the difference in the magnitude of CO2 efflux between trees
of different age and size. No relationship was found between efflux and sap flow, and efflux was independent of tree
volume, suggesting the presence of substantial barriers to the diffusion of CO2 from the xylem to the atmosphere in
this species. The rate of corticular photosynthesis was the same in trees of both ages and only reduced CO2 efflux by
7%, probably due to the low irradiance at the stem surface below the canopy. The younger trees were growing at
a much faster rate than the older trees. The difference between CO2 efflux from the younger and older stems appears
to have resulted from a difference in growth respiration rather than a difference in the rate of diffusion of xylemtransported
CO2
Descrição
Research Paper
Palavras-chave
Eucalyptus globulus refixation stem respiration
Contexto Educativo
Citação
"Journal of Experimental Botany". ISSN 0022-0957. 60(1) (2009) p.99-105
Editora
Oxford University Press