Portal de Periódicos da CAPES

Transpiration and stomatal conductance of two rain forest species growing in plantations (Simarouba amara and Goupia glabra) in French Guyana

1992; EDP Sciences; Volume: 49; Issue: 1 Linguagem: Inglês

10.1051/forest

1878-6545

André Granier, Roland Huc, Francis Colin,

African Botany and Ecology Studies

Water relations of 2 tree species from the tropical rain forest of French Guyana were studied in young plantations of Simarouba amara and Goupia glabra.Experiments took place in 1988 and 1989.Sap flow was recorded continuously for several months including a dry season.On bright days, sap flux densities (eg sap flow per unit of conducting area) exhibited high values of ≈ 3.5 to 4.0 kg.dm -2 .h-1 .Total sap flow differed from one tree to another depending on individual sapwood areas.In spite of the increase of global radiation and of the vapour pressure deficit, sap flow re- mained constant for Simarouba and even decreased for Goupia between 10:00 and 15:00 h as a consequence of stomatal closure.Sap flow measurements allowed the calculation of stand transpiration, which for bright days represented only 50% of Penman potential evapotranspiration (PET).This low transpiration level was explained by incomplete canopy closure and hence a low LAI of the plots.Canopy conductances were calculated from the Penman-Monteith equation.They demon- strated the inhibiting effect of vapour pressure deficits > 4 hPa.These results confirm those of Huc and Guehl (1989), that for tropical rain forest species, transpiration may be limited by stomatal clo- sure notwithstanding a high annual rainfall.permis d'évaluer la transpiration des placeaux, ne représentant environ que 50% de l'ETP Penman pour les belles journées.Ce faible pourcentage a été rapproché du faible indice foliaire de ces jeunes plantations non encore fermées.Un calcul des conductances de couvert a été réalisé à partir de la formule de Penman-Monteith, en assimilant les flux de sève à la transpiration.Les valeurs de conduc- tance ainsi obtenues ont montré un effet négatif important de la sécheresse de l'air, dès que le déficit de saturation dépassait 4 hPa.Les comportements ainsi mis en évidence confirment, après les résul- tats de Huc et Guehl (1989) que chez ces espèces, une fermeture stomatique peut intervenir, malgré une pluviométrie annuelle élevée.transpiration / flux de sève / conductance stomatique / humidité de l'air / espèces tropicales / conductance du couvert