Interpreting species‐specific variation in tree‐ring oxygen isotope ratios among three temperate forest trees

Abstract

Although considerable variation has been documented in tree-ring cellulose oxygen isotope ratios (δ(18)O(cell)) among co-occurring species, the underlying causes are unknown. Here, we used a combination of field measurements and modelling to investigate the mechanisms behind variations in late-wood δ(18) O(cell) (δ(18)O(lc)) among three co-occurring species (chestnut oak, black oak and pitch pine) in a temperate forest. For two growing seasons, we quantified among-species variation in δ(18)O(lc), as well as several variables that could potentially cause the δ(18)O(lc) variation. Data analysis based on the δ(18) O(cell) model rules out leaf water enrichment (Δ(18)O(lw)) and tree-ring formation period (Δt), but highlights source water δ(18) O (δ(18) O(sw)) as an important driver for the measured difference in δ(18)O(lc) between black and chestnut oak. However, the enriched δ(18)O(lc) in pitch pine relative to the oaks could not be sufficiently explained by consideration of the above three variables only, but rather, we show that differences in the proportion of oxygen exchange during cellulose synthesis (p(ex)) is most likely a key mechanism. Our demonstration of the relevance of some species-specific features (or lack thereof) to δ(18)O(cell) has important implications for isotope based ecophysiological/paleoclimate studies.

Nitrogen fertilization and δ18O of CO2 have no effect on 18O‐enrichment of leaf water and cellulose in Cleistogenes squarrosa (C4) – is VPD the sole control?

“…; Song et al . ), this is the first experimental assessment of a δ 18 O CO2 effect on δ 18 O of cellulose in a C 4 plant species, and the first verification of the reported absence of such an effect by DeNiro & Epstein (). The absence of a significant effect of δ 18 O CO2 on δ 18 O Cel means that carbonic anhydrase activity of C .…”

Measurements of transpiration isotopologues and leaf water to assess enrichment models in cotton

“…Considering that the Péclet effect is difficult to parameterize in many situations, the circumvention of the Péclet correction in the context of the two‐pool model would therefore represent a significant simplification of the parameterization process when it comes to δ 18 O cell modeling. However, we note that previous studies have also presented evidence in support of (either directly or indirectly) the use of the Péclet correction for modeling δ 18 O cell (Cernusak et al ., ; Barbour et al ., ; Gessler et al ., ; Song et al ., ). Therefore, more work on the relationship of leaf water enrichment with δ 18 O of phloem sap carbohydrates and δ 18 O cell is needed to reconcile the discrepancy in results.…”

Recovery following defoliation involves shifts in allocation that favour storage and reproduction over radial growth in black oak

“…Precipitation is generally distributed equally throughout the year, though late summer droughts are common. The 2010 growing season received less than half the rainfall received in 2011 (Song, Clark & Helliker ).…”