Temperature versus species-specific influences on the stable oxygen isotope ratio of tree rings

Abstract

Stable isotopic ratios integrate ecosystem variability while reflecting change in both environmental and biological processes. At sites, where climate does not strongly limit tree growth, co-occurring trees may display large discrepancies in stable oxygen isotopic ratios (d 18 O) due to the interplay between biological processes (competition for light and nutrients, individual tree physiology, etc.) and climate. For a better quantification of the isotope variability within and among trees, the climatic and/or individual tree effects on seasonal d 18 O variations in precipitation, soil water, leaf water and leaf organic material (whole leaf, cellulose and starch) and annual d 18 O variations in tree-ring cellulose for Fagus sylvatica (Fs), Quercus robur (Qr), Carpinus betulus (Cb) and Pinus sylvestris (Ps) were studied in a mature temperate forest in Switzerland, using a mixed linear regression model technique. Furthermore, the influence of environmental factors on d 18 O was assessed by means of three common isotope fractionation models. Our statistical analysis showed that except for Ps, a greater portion of d 18 O variance in leaf compounds can be explained by individual tree effects, compared to temperature. Concerning tree-ring cellulose, only Fs and Ps show a significant temperature signal (maximum 12% of the variance explained), while the individual tree effect significantly explains d 18 O for all species for a period of 38 years. Large species differences resulted in a limited ability of the isotope fractionation models to predict measured values. Overall, we conclude that in a diverse mixed forest stand, individual tree responses reduce the potential extraction of a temperature signal from d 18 O.

Comparisons of the Performance of δ13C and δ18O of Fagus sylvatica, Pinus sylvestris, and Quercus petraea in the Record of Past Climate Variations

“…The mean δ 18 O of P. sylvestris cellulose was 1‰ higher than the one of F. sylvatica , which was 0.6‰ higher than the one of Q. petraea . Reynolds‐Henne et al () measured differences about 50% larger (1.5‰ between P. sylvestris and F. sylvatica and 1‰ between the latter and Q. robur ). Szczepanek et al () obtained intermediary results, with a difference between Q. robur and P. sylvestris of 2.1 ‰.…”

Seasonal temperature and precipitation recorded in the intra-annual oxygen isotope pattern of meteoric water and tree-ring cellulose

“…However, a unifying relationship for interpreting observed patterns in d 18 O cell extracted from across tree-rings is lacking. Multiple studies have shown that individual trees may have different d 18 O cell absolute values, even when growing at the same site, under the same conditions (Reynolds-Henne et al, 2009;Richter et al, 2008b;Wang et al, 1998) and authors have concluded that the search for a single environmental signal to explain absolute d 18 O cell values across all sites is futile (McCarroll and Loader, 2004). We have shown elsewhere that the relative change in the carbon isotope (d 13 C) values measured from intra-ring profiles provides valuable quantitative paleoclimate information, despite the fact that absolute values of d 13 C in wood differed between individual trees at the same site (Schubert and Jahren, 2011).…”

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

“…; Reynolds‐Henne et al . ), the underlying mechanisms behind species‐specific affect on δ 18 O cell is currently not well understood. Presumably, such a lack of understanding of δ 18 O cell variability is largely due to the complex involvement of many environmental and physiological factors in influencing δ 18 O cell , thereby impeding precise identification of the source(s) of variation.…”

“…Using δ 18 Ocell to reconstruct past climates, or tree physiological responses to climate, requires knowledge of both isotopic variation among individual trees within a given species, and isotopic variation among the species that co-occur at the site (McCarroll & Loader 2004;Leavitt 2010). While co-occurring tree species have been documented to exhibit marked variation in their δ 18 Ocell (Marshall & Monserud 2006;Richter et al 2008;Gebrekirstos et al 2009;Reynolds-Henne et al 2009), the underlying mechanisms behind species-specific affect on δ 18 Ocell is currently not well understood. Presumably, such a lack of understanding of δ 18 Ocell variability is largely due to the complex involvement of many environmental and physiological factors in influencing δ 18 Ocell, thereby impeding precise identification of the source(s) of variation.…”