The regulation of sapwood area, water transport and heartwood formation in Sitka spruce. (Special Issue: John Grace Festschrift - forest and environment.)

摘要

Background: The mechanism by which water transport, tree growth and heartwood formation are balanced is poorly understood. Aims: To test the hypothesis that xylem formation drives heartwood production through changes in water transport to regulate sapwood area. Methods: We measured changes in sap flux at multiple depths across the sapwood to heartwood boundary in Sitka spruce (Picea sitchensis) from May 2009-October 2010 using the Heat Field Deformation method. Results: The radial sap flux profile was peaked with maximum flux occurring 1-2 cm below bark before reducing to the heartwood boundary (tail). Changes occurred in two stages. The depth of peak sap flux (D) extended outwards as new xylem formed during the growing season, giving an annual increment (AI). Water transport reduced in the tail sometime during dormancy, from November to March. The correlation between AI and D was good however, these variables and the increase in sapwood area correlated poorly with the extent of heartwood formed. Conclusions: Heartwood formed during the dormant period in Sitka spruce in Great Britain. Xylem formation did not directly drive heartwood production; however, changes in specific conductivity need consideration. Reduced transport in the inner sapwood could provide a temporal signal for heartwood formation in pre-conditioned cells.Digital Object Identifier http://dx.doi.org/10.1080/17550874.2012.702359