Fertilization effects on mean stomatal conductance are mediated through changes in the hydraulic attributes of mature Norway spruce trees
| Title | Fertilization effects on mean stomatal conductance are mediated through changes in the hydraulic attributes of mature Norway spruce trees |
| Publication Type | Journal Article |
| Year of Publication | 2008 |
| Authors | Ward, EJ, Oren R, Sigurdsson BD, Jarvis PG, Linder S |
| Journal | Tree Physiol |
| Volume | 28 |
| Pagination | 579-596 |
| Abstract | Stomatal conductance was quantified with sap flux sensors and whole-tree chambers in mature Norway spruce (Picea abies (L.) Karst.) trees after 3 years of exposure to elevated CO2 concentration ([CO2]) in a 13-year nutrient optimization experiment. The long-term nutrient optimization treatment increased tree height by 3.7 m (67%) and basal diameter by 8 cm (68%); the short-term elevated [CO2] exposure had no effect on tree size or allometry. Nighttime transpiration was estimated as [ ]7% of daily transpiration in unchambered trees; accounting for the effect of nighttime flux on the processing of sap flux signals increased estimated daily water uptake by [ ]30%. Crown averaged stomatal conductance (gs) was described by a Jarvis-type model. The addition of a stomatal response time constant ({tau}) and total capacitance of stored water (Ctot) improved the fit of the model. Model estimates for Ctot scaled with sapwood volume of the bole in fertilized trees. Hydraulic support–defined as a lumped variable of leaf-specific hydraulic conductivity and water potential gradient (Kl{Delta}{Psi}) –was estimated from height, sapwood-to-leaf area ratio (As:Al) and changes in tracheid dimensions. Hydraulic support explained 55% of the variation in gs at reference conditions for trees across nutrient and [CO2] treatments. Removal of [ ]50% of Al from three trees yielded results suggesting that stomatal compensation (i.e., an increase in gs) after pruning scales inversely with Kl{Delta}{Psi}, indicating that the higher the potential hydraulic support after pruning, the less complete the stomatal compensation for the increase in As:Al. |
| URL | http://treephys.oxfordjournals.org/cgi/content/abstract/28/4/579 |
| DOI | 10.1093/treephys/28.4.579 |