Linkages between water transport, hydraulic architecture and carbon assimilation in woody species

BUCCI SANDRA

Hyytiälä forestry field station

Workshop; XI INTERNATIONAL WORKSHOP OF SAP FLOW; 2019

INTERNATIONAL SOCIETY FOR HORTICULTURAL SCIENCE

Water storage and transport play animportant role in whole-plant water carbon balance. Different patterns of diurnalvariation in sap flow, water content in stem tissues and changes in crosssectional area were observed. A typical diurnal pattern showed an increase insapflow during the morning with the decrease in sapwood and bark tissue watercontent consistent with the shrinkage of the stems. This pattern stronglysuggests that the internal water storages contribute to the leaf water consumption.However, other pattern also was observed in a species with an atypical extremelythick cortex. Water stem reservoirs were recharged during the daytime when thesap flow was substantially high. A third pattern was observed in species withvery high wood density, where stem sectional area decreased when sap flowincreased and sapwood water storages were recharged.  The functional significance for thesedifferent patterns will be discussed.       Thecoordination between capacitance and hydraulic efficiency across leaves andstems of tree species was also evaluated, including the linkages between thesehydraulic traits and vulnerability to drought and the assimilation rates. Specieswith higher capacitance and hydraulic efficiency were more vulnerable todrought, had narrow safety margin and restricted transpiration and carbonassimilation earlier in the daytime. We will discuss also the consequences ofthese patterns under drought anomalies.