Abstract
We investigated how water and nutrient availability affect radiation-use effeciency (e) and assessed leaf gas exchange as a possible mechanism for shifts in e. We measured aboveground net primary production (ANPP) and annual photosynthetically active radiation (PAR) capture to calculate e as well as leaf-level physiological variables (light-saturated net photosynthesis, A
sat; stomatal conductance, g
s; leaf internal CO
2 concentration, C; foliar nitrogen concentration, foliar [N]; and midday leaf water potential during the second (2001) and third (2002) growing seasons in sweetgum (
Liquidambar styraciflua L.) and sycamore (
Platanus occidentalis L.) stands receiving a factorial combination of irrigation and fertilization at the Savannah River Site, South Carolina. Irrigation and fertilization in creased PAR capture (maximum increase 60%) in 2001 and 2002 for both species and annual PAR capture was well correlated with ANPP (mean r
2 = 0.77). A decreasing trend in e was observed in non-irrigated stands for sweetgum in 2001 and for sycamore in both years, although this was only significant for sycamore in 2002. Irrigated stands maintained higher gas exchange rates than non-irrigated stands for sweetgum in 2001 and for sycamore in both years, although foliar [N] and T
leaf were generally unaffected. Because C
1 decreased in proportion to g
s in non-irrigated stands, it appeared that greater stomatal limitations of photosynthesis was associated with decreased A
sat. On several measurement dates for sweetgum in 2001 and for sycamore in both years, e was positively correlated with gas exchange variables (A
sat, g
s, C
i (r ranged from 0.600 to 0.857). These results indicate that PAR capture is well correlated with ANPP and that gas exchange rates modified by irrigation cna influence the conversion of captured light energy to biomass.
Keywords
fertilization,
intercepted radiation,
irrigation,
Liquidambar styraciflua,
photosynthesis,
Plantanus occidentalis
Citation
Allen, Christopher B.; Will, Rodney E.; McGravey, Robert C.; Coyle, David R.; Coleman, Mark D. 2005. Radiation-use efficiency and gas exchange responses to water and nutrient availability in irrigated and fertilized stands of sweetgum and sycamore. Tree Physiology 25, 191-200. Victoria, Canada.