%0 Journal Article
%T Transpira  o pelo m¨¦todo da sonda de dissipa  o t¨¦rmica em floresta de transi  o Amaz nica-Cerrado Transpiration by the heat dissipation probe method in transition Amazon-Savannah forest
%A Osvaldo B. Pinto Jr.
%A George L. Vourlitis
%A Luciana Sanches
%A Higo J. Dalmagro
%J Revista Brasileira de Engenharia Agr¨ªcola e Ambiental
%D 2013
%I Departamento de Engenharia Agr¨ªcola - UFCG
%X Com este trabalho objetivou-se analisar o comportamento do fluxo de seiva em esp¨¦cies da floresta de transi  o Amaz nia Cerrado e caracterizar a depend¨ºncia do fluxo de seiva, em fun  o do d¨¦ficit de press o de vapor da atmosfera (DPV). O fluxo de seiva foi medido utilizando-se sondas de dissipa  o t¨¦rmica em 5 esp¨¦cies diferentes. Os dados foram divididos em quatro esta  es. No per¨ªodo experimental as curvas de varia  o sazonal do fluxo de seiva evidenciam a ocorr¨ºncia de picos no per¨ªodo ¨²mido. Esta tend¨ºncia sazonal do fluxo de seiva foi evidenciada pela rela  o entre valores di¨¢rios de transpira  o e do DPV. O valor limite do DPV nessas esta  es foi de 1 a 1,5 kPa. Com refer¨ºncia ao fluxo de seiva como representativo da taxa transpirat¨®ria das plantas, a redu  o do fluxo no per¨ªodo seco n o confirma a hip¨®tese da manuten  o do processo de evapotranspira  o. O fluxo de seiva nas esp¨¦cies do estudo ¨¦ influenciado mais pelas condi  es atmosf¨¦ricas do que mesmo pela disponibilidade de ¨¢gua no solo, o que suscita um poss¨ªvel armazenamento da ¨¢gua no caule nos per¨ªodos mais secos quando a ¨¢rea foliar diminui mas a taxa transpirat¨®ria n o ¨¦ significativamente distinta daquela do per¨ªodo chuvoso. The objective of this study was to analyse the behavior of sap flow in a transition Amazon-Savannah forest species, to characterize the dependence of sap flow as a function of atmospheric vapor pressure deficit (VPD). The sap flow was measured using the technique proposed by Granier, using heat dissipation probes in five different species. The data were divided into four seasons. In the experimental period, the curves of seasonal variation of sap flow showed an occurrence of peaks in the wet season. This seasonal sap flow trend was evidenced by the relationship between daily values of transpiration and VPD. The threshold value of VPD at these stations ranged from 1 to 1.5 kPa. Considering sap flow as representative of plant transpiration, reduction of the flux in the dry season did not confirm the hypothesis of maintenance of evapotranspiration process. The sap flow in the studied species was influenced more by weather than soil water availability. This raises the possibility of water storage in the stem during drier periods, when leaf area decreases. However the transpiration rate is not significantly different from that of the rainy season.
%K fluxo de seiva
%K evapotranspira  o
%K armazenamento de ¨¢gua
%K sap flow
%K evapotranspiration
%K water storage
%U http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-43662013000300004