Twentieth century trends in tree ring stable isotopes (δ¹³C and δ¹⁸O) of Larix sibirica under dry conditions in the forest steppe in Siberia

Abstract

[1] Tree ring width, density, and ratio of stable isotopes ( 13 C/ 12 C and 18 O/ 16 O) in wood and cellulose were determined for larch (Larix sibirica Ledeb.) growing under water deficit conditions in the forest steppe zone in central Siberia (54°24′N, 89°57′E) for the period 1850-2005. Dendroclimatic analysis of the chronologies indicated precipitation to be the most important factor determining indicated parameters. Precipitation of June is significantly correlated with tree ring width and maximum density (r = 0.36 and 0.43, p < 0.05, respectively). Relations of d 13 C and d 18 O to precipitation are similar, but the most important month is July (r = −0.47, p < 0.05 for d 13 C; r = −0.29, p < 0.05 for18 O is positively related to the mean temperatures of July (r = 0.30, p < 0.05). Carbon and oxygen isotope ratios in wood and cellulose showed strong negative trends for the last 100 years. The reason for this decrease could be the observed shift of the beginning of the vegetation period to earlier dates (up to 1 week) in spring and the increased use of precipitation water stored in the soil from October of the previous year, although other explanations cannot be excluded (in particular the physiological effect of increasing atmospheric CO 2 also responsible for lower d13 C values). Thus, an earlier start of the vegetation period could lead to tree ring formation during a period with higher water availability, resulting in stronger isotopic fractionation and 13 C depletion, also reflected in a higher earlywood to latewood ratio. At the same time, highly 18 O depleted water from October precipitation of the previous year is absorbed. The incorporation of this isotopically lighter water during photosynthesis is reflected in the wood and cellulose of tree rings.

Progress and challenges in using stable isotopes to trace plant carbon and water relations across scales

“…δ 18 O of bulk organic matter has also been used to determine whether a change in WUE i results from the increase in atmospheric CO 2 (Saurer and Siegwolf, 2007). Also, the effects of changes in vapor pressure deficit (VPD) resulting from increasing temperature or decreasing precipitation have been assessed along a Siberian transect (Sidorova et al, 2009;Knorre et al, 2010). The dual-isotope approach has proven a valuable concept for ecological applications.…”

“…Tree rings enable retrospective analyses of intra-and interannual variation of carbon and oxygen isotope composition and the related ecophysiological drivers over many centuries (Sidorova et al, 2009;Nock et al, 2010;Knorre et al, 2010;Andreu-Hayles et al, 2011;Peñuelas et al, 2011). The advantages of tree rings are that they (i) can be reliably dated with a high temporal and spatial resolution; (ii) contain several proxies (stable C, H, O and N isotopes, tree ring width and tree ring density) in the same matrix (tree ring wood/cellulose), which was formed at the same time, location, and environmental conditions; and (iii) mostly the inclusion of a limited number of trees and species may provide a strong signal.…”

Warming Effects on Pinus sylvestris in the Cold–Dry Siberian Forest–Steppe: Positive or Negative Balance of Trade?

“…Here, we assess climate effects on physiological processes underlying tree growth patterns in two contrasting sites with regard to climate trends that are located near the moisture limit of the species range at the southern edge of the boreal forest belt. This area offers an excellent opportunity to test for global change impacts on forests growing under the combined effects of low temperatures and water scarcity [34]. These interactions may expose trees to previously untested bioclimatic envelopes, perhaps resulting in a relaxation of cold limitation modifying phenology and an exacerbation of drought effects impacting on carbon and water budgets.…”

The response of δ13C, δ18O and cell anatomy of Larix gmelinii tree rings to differing soil active layer depths

“…The combination of the stable C and O isotopes (dual isotope approach) facilitates the distinction between stomatal and photosynthetic responses (Scheidegger et al, 2000). Based on this approach it is possible to derive the impact of temperature and water availability as the driving climatic parameter (Sidorova et al, 2009;Knorre et al, 2010;Roden and Farquhar, 2012). Tree-ring anatomy measured in series of tree rings provides additional information about xylem functional adjustment to varying environmental conditions (e.g.…”