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

• Published in: Trees (Berlin, West) West), 2009-08, Vol.23 (4), p.801-811
• Main Authors: Reynolds-Henne, Christina E, Saurer, Matthias, Siegwolf, Rolf T. W
• Format: Article
• Language: English
• Subjects: Agriculture; Biomedical and Life Sciences; Carpinus betulus; Cellulose; Environmental factors; Fagus sylvatica; Forestry; Fractionation; Isotope fractionation; Isotopes; Leaves; Life Sciences; Mixed forests; Moisture content; Original Paper; Oxygen isotope ratio; Oxygen isotopes; Pine trees; Pinus sylvestris; Plant Anatomy/Development; Plant Pathology; Plant Physiology; Plant Sciences; Quercus robur; Soil water; Statistical analysis; Temperate forests; Temperature; Trees
• ISSN: 0931-1890; 1432-2285
• DOI: 10.1007/s00468-009-0321-4

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 (δ¹⁸O) 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 δ¹⁸O variations in precipitation, soil water, leaf water and leaf organic material (whole leaf, cellulose and starch) and annual δ¹⁸O 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 δ¹⁸O was assessed by means of three common isotope fractionation models. Our statistical analysis showed that except for Ps, a greater portion of δ¹⁸O 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 δ¹⁸O 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 δ¹⁸O.