Effect of carbon dioxide, fertilization and irrigation on loblolly pine branch morphology

Abstract

AbstractmFoliage and wood parameters of branches of 12-year-old loblolly pine (Pinus taeda L.) trees were characterized after 21 months of exposure to fertilizer, irrigation and elevated CO2 treatments. Branches of loblolly pine trees were enclosed in plastic chambers and exposed to ambient, ambient +175 and ambient +350 umol mol -1 CO2 concentrations. Measurements of foliage and wood at the fascicle, flush and branch levels were made at the end of the 21 month study period. The +350 CO2 treatment did not significantly increase fascicle radius or length but did increase the number of fascicles on the first flush. Fertilization significantly increased fascicle radius and length, while irrigation significantly increased number of fascicles and flush length of first flush. The +350 CO2 treatment also significantly increased flush length of the first flush. Significant interaction of fertilization and irrigation with CO2 was observed for fascicle length. Significant interactions of fertilization and irrigation were also observed for flush length, number of fascicles and fascicle length. Observed increases in fascicle radius, fascicle length, number of fascicles and flush length may have been responsible for the significantly higher flush leaf area observed for the all three treatments. Also, a combination of fertilization and irrigation increased leaf area by 82% compared to that in the control when averaged across CO2 treatments. At the branch level +350 CO2 treatment significantly increased shoot length but not the number of flushes on the branch. In general with the exception of bark density and total number of needle scales, neither fertilization nor irrigation had any significant effect on other branch level parameters. Results from this study indicate that with 'global change' an increase in CO2 alone may increase leaf area via an increase in flush length and number of fascicles. Combining increases in CO2 with fertilization and irrigation could greatly enhance leaf area which when coupled to observed increases in net photosynthesis as a result of elevated CO2 could greatly increase productivity of loblolly pine trees.

The effects of annual fertilization and complete competition control on fascicle morphology of different aged loblolly pine stands

“…Two previous studies in loblolly pine found that high nutrient availability was associated with longer and thicker fascicles (Shelton and Switzer 1984;Murthy and Dougherty 1997). In one study, however, fertilization decreased SNA (Murthy and Dougherty 1997) and in the other, good site quality was associated with increased SNA (Shelton and Switzer 1984).…”

“…In general, greater nutrient availability increases foliage dimensions of Pinus (Shelton and Switzer 1984;Conroy et al 1986;Gholz 1986;Raison et al 1992;Murthy and Dougherty 1997;Niinemets et al 2001). The extent that leaf dimensions are plastic in response to nutrient supply may have important implications regarding the ability of canopies to adjust their capacity to capture light and photosynthesize.…”

“…However, separating nutrient availability from light is difficult since greater resource availability increases canopy size and also increases shading within the canopy. For instance, high nutrient availability has been shown to increase (Shelton and Switzer 1984;Raison et al 1992; Thompson and Wheeler 1992) or decrease (Benecke 1979;Norgren 1996;Murthy and Dougherty 1997;Niinemets et al 2001) SNA of Pinus. These contradictory findings are probably a result of confounding the effects of light with those of nutrition (Niinemets et al 2001).…”

Needle longevity, shoot growth and branching frequency in relation to site fertility and within-canopy light conditions in Pinus sylvestris

“…There is evidence that, in conifers, branchiness may increase with decreasing site water availability [5]. In addition, increases in soil nutrient availability generally lead to enhanced branch extension growth [47,67], as well as higher fractional biomass investment in foliage [59], and greater total plant foliar area [47,70,73]. The branching responses to nutrient availability have not been investigated extensively in trees, and it is not clear whether the nutrientrelated increase in branch extension is sufficient to support the extra foliar area, or whether the improved nutrition also leads to greater shoot production and more frequent branching.…”

Influence of stand density, thinning and elevated CO₂ on stem wood density of spruce

“…However, Pinus taeda did not respond to elevated CO 2 unambiguously. SWD of this species was increased (Doyle 1987) or decreased (Oren et al 2001) and also remained stable (Murthy, Dougherty 1997;Telewski et al 1999;Roderick 2001). These inconsistent results obtained for individual coniferous species can be also caused by differences in cultivation design and also in fumigation duration.…”