Impact of gas emissions from oil and gas reservoirs on stable carbon isotope variability in tree rings

Accelerated development of energy resources around the world has significantly increased forest change associated with oil and gas activities, leading to both carbon dioxide and methane emissions. The impacts of these anthropogenic indirect greenhouse gases play a significant role on forest ecosystems at the regional and global scales.

In this study we aim to reveal site-specific differences in stable carbon isotope (δ¹³С) variability of pine trees (Pinus sylvestris) growing on the territory of (i) oil and gas reservoirs located in Almetyevsk and Leninogorsk regions (Tatarstan Republic, Russian Federation) classified as “disturbed”; and (ii) in a remote “undisturbed” site in Raifa, which is located ca. 250 km away from the oil and gas deposits.

Tree cores were sampled from the south- and north-facing sides of each of the nine trees for both study sites using a Pressler increment borer. The state-of-the-art classical dendrochronological method was applied for the tree-ring width measurements and cross-dating. Each annual ring was split using a sharp BA-170P NT blade under the Leica M50 microscope. Stable carbon isotope measurements were performed for each year separately using a Delta V Plus isotope mass spectrometer (Thermo Fisher Scientific, Germany) via a Flash HT Plus in constant flow mode. Based on the nine individual trees stable carbon isotope chronologies were developed from 1930 to 2022. Tree-ring δ¹³C in wood chronologies were corrected according to δ¹³C atmospheric CO₂ for both study sites.

Results of our study indicate significant differences between carbon isotope variability in tree rings from “disturbed” the oil and gas deposits site, which is rapidly developed over the recent decades compared to the “undisturbed” natural forest site.

This work was funded by the Kazan Federal University Strategic Academic Leadership Program (PRIORITY-2030).