Testing the ecophysiological basis for the control of monoterpene concentrations in thinned and unthinned balsam fir stands across different drainage classes

Abstract

Stand thinning across different soil drainage types was used to test the ecophysiological basis for the control of foliar monoterpenes in current-year foliage of balsam trees [Abies balsamea (L.) P. Mill.] the year following treatment. Photosynthetic capacity (A ) was greater on mesic sites than on sub-hygric and hydric sites (1.81, 1.33 and 0.88 µmol m s, respectively) and greater in mid-July than at the end of June (1.86 vs 0.77 µmol m s). Foliar N was greater on thinned plots than control plots (2.6 vs 2.2 g m); starch was greater on mesic control plots than mesic thinned plots (16.3 vs 10.9 g m); and total soluble sugars (TSS) were higher in mid-July than at the end of June (16.5 vs 12.8 g m). Total monoterpenes, as well as five individual monoterpenes, showed a complex interaction between site drainage class, thinning treatment and time of sampling (P<0.05). For all sites and dates combined, total monoterpenes were negatively correlated with specific leaf area (r =0.46), and positively but weakly correlated with A (r =0.35), foliar N (r=0.29) and TSS (r =0.24). Total monoterpenes were not correlated with the different measures of carbon to nitrogen ratio as predicted by the carbon-nutrient balance hypothesis. Our results offer partial support to the different hypotheses proposing that foliage having greater resource availability, enzymatic machinery and potential for building storage structures will have greater monoterpene content. However, the strength of the relationships with monoterpenes often varied with sampling date, suggesting that phenological development may play a strong role in determining which factors control monoterpenes at a given time.

Growth and physiological response of eastern white pine seedlings to partial cutting and site preparation

“…However, many factors can contribute to a lack of correlation between leaf N and A. The most likely are growth dilution of N with increasing LMA (Ellsworth and Reich, 1992;Castro-Díez et al, 2000), withinleaf allocation of N to other non-photosynthetic tissue (Abrams and Mostoller, 1995;Lamontagne et al, 2002), and the retranslocation of photosynthates and nutrients between current-year and 1-year old foliage (Maier and Teskey, 1992;Munson et al, 1995).…”

Carbon allocation during defoliation: testing a defense-growth trade-off in balsam fir

“…Needles of conifers contain secondary metabolites with defense functions ( Schonwitz et al, 1991 ; Carlow et al, 2006 ), of which monoterpenes are the dominant ones in resin ( Trowbridge et al, 2014 ). Their mechanisms of production are still poorly understood because several factors such as available nutrients ( Lamontagne et al, 2000 , 2002 ), water, C-reserve ( Trowbridge et al, 2014 ), and light ( Niinemets et al, 2004 ) influence their production. The concentration of monoterpenes can also be affected by the emission of volatile compounds ( Trowbridge et al, 2014 ) and their physicochemical characteristics such as volatility, solubility, and diffusivity ( Niinemets et al, 2004 ; Niinemets, 2010 ; Blanch et al, 2011 ).…”

Ecophysiological responses of two herbaceous species to prescribed burning, alone or in combination with overstory thinning

“…Many previous studies have demonstrated that ecophysiological characteristics change in response to natural ranges of altitude, moisture, light gradients, and soil N availability (Kubiske and Abrams, 1992;Dudley, 1996;Muraoka et al, 1997;Jonas and Geber, 1999), as well as to gaseous air pollutants in controlled growth environments (Loats and Rebbeck, 1999). Recent ecosystem level studies have addressed the manner in which different treatments, such as prescribed burning and restoration thinning, affect fine-scale differences in leaf ecophysiological responses such as photosynthesis, nutrient concentration, and instantaneous nutrient use efficiency (Reich et al, 1990;Kruger and Reich, 1997;Fleck et al, 1998;Lamontagne et al, 2002;Wallin et al, 2004).…”