Time course of  13C in poplar wood: genotype ranking remains stable over the life cycle in plantations despite some differences between cellulose and bulk wood

Abstract

Genetic differences in δ¹³C (isotopic composition of dry matter carbon) have been evidenced among poplar genotypes at juvenile stages. To check whether such differences were maintained with age in trees growing in plantations, we investigated the time course of δ¹³C as recorded in annual tree rings from different genotypes growing at three sites in southwestern France and felled at ∼15-17 years. Wood cores were cut from tree discs to record the time course of annual basal area increment (BAI). The isotopic ratio δ¹³C was recorded in bulk wood and in extracted cellulose from the annual rings corresponding to the period 1996-2005. Discrimination against ¹³C between atmosphere and tissues (Δ¹³C) was computed by taking into account the inter-annual time course of δ¹³C in the atmosphere. Annual BAI increased steadily and stabilized at about 8 years. An offset in δ¹³C of ∼1‰ was recorded between extracted cellulose and bulk wood. It was relatively stable among genotypes within sites but varied among sites and increased slightly with age. Site effects as well as genotype differences were detected in Δ¹³C recorded from the cellulose fraction. Absolute values as well as the genotype ranking of Δ¹³C remained stable with age in the three sites. Genotype means of Δ¹³C were not correlated to annual BAI. We conclude that genotypic differences of Δ¹³C occur in older poplar trees in plantations, and that the differences as well as the genotype ranking remain stable while trees age until harvest.

Carbon isotope compositions (δ13C) of leaf, wood and holocellulose differ among genotypes of poplar and between previous land uses in a short‐rotation biomass plantation

“…Although these differences were not sufficient to alter the genotype ranking, our results suggest that δ 13 Cwood may not provide a reliable and consistent signal for inter-genotype comparisons, even for juvenile trees such as those studied here. This is only partly confirmatory of the findings reported by Rasheed et al (2011) on several hybrid poplars. In their study, the δ 13 C offset significantly differed among genotypes at only one study site while no difference was detected at the two other sites.…”

“…Because of the presence of lignin in bulk wood, which is 3-5‰ more depleted in 13 C than cellulose (Benner et al 1987;Loader et al 2003), the offset in δ 13 C between bulk tissue and cellulose is generally in the range of 0.5-2.0‰ (Borella et al 1998;Loader et al 2003;Verheyden et al 2005;Harlow et al 2006;Rasheed et al 2011;Szymczak et al 2011). The average δ 13 C offset of 0.92‰ found in our study fitted within this range, although near the lower end.The fact that the cellulose extracted in our study corresponded to holocellulose, not to purified α-cellulose, may partly explain this.…”

“…Whether this will remain true with tree ageing remains to be analysed. Recent data on 15-to 17-year-old poplar genotypes have indicated that tree ring δ 13 C and growth based on annual basal area increment remained unrelated over time (Rasheed et al 2011).…”

Seasonal variations in photosynthesis, intrinsic water-use efficiency and stable isotope composition of poplar leaves in a short-rotation plantation

“…Previous studies on poplars have suggested that variations among genotypes are generally driven by variations in g s (Monclus et al 2006, Fichot et al 2011, Rasheed et al 2011, Cao et al 2012) although one opposite result has been reported (Rasheed et al 2013). Our results suggest that variations in WUE i across dates and genotypes were primarily driven by variations in g s-sat .…”

Hydrologic linkages between a climate oscillation, river flows, growth, and wood Δ13C of male and female cottonwood trees

“…D 13 C in bulk wood, such as these samples, is expected to provide a similar or stronger relationship to climatic parameters as D 13 C in cellulose or lignin (Loader, Robertson & McCarroll 2003). D 13 C in lignin is higher than that in cellulose, however, and so D 13 C in bulk wood of poplars is expected to be higher than that in cellulose (Loader et al 2003;Rasheed et al 2011). The difference may be constant from year to year (Loader et al 2003), or may increase gradually with age (Rasheed et al 2011).…”