Isotope applications to soil science at the University of Alberta — an historical perspective

Abstract

For the past 70 yr, researchers in the Soil Science/Renewable Resources Department at the University of Alberta have used isotopes to study topics of ecological importance. This review highlights the soil isotope research conducted within our department over this time, including an historical overview of studies of interest. Analytical techniques and advances in instrumentation are discussed, focusing on the measurement of light stable isotope ratios (i.e., for C, H, N, S, and O) using isotope ratio mass spectrometry (IRMS). Early soil isotope work (1950–2000s) focused on agricultural soils and soil fertility issues. These studies included the use of radioactive isotopes such as 14C and 35S, and (or) artificially enriched stable isotopes including 15N-labelled fertilizers. More recently (2000–present), the scope of research widened to include natural-abundance stable isotope ratio studies as higher-sensitivity IRMS systems became more prevalent. Current isotope research topics include N biogeochemistry in natural and managed ecosystems, land management effects on greenhouse gas emissions, carbon cycling in northern landscapes, paleo-reconstruction in peatlands, carbon sequestration in boreal forests, and biodegradation of petroleum hydrocarbons. Further technological progress also enabled new techniques such as compound-specific IRMS analysis, including δ13C and δ2H measurements of soil n-alkanes and phospholipid fatty acids. In conclusion, current IRMS instrumentation presents unparalleled opportunities for multidisciplinary research to track carbon, plant nutrients, and pollutants as they move through soils.

Nitrogen Use Efficiency Using the 15N Dilution Technique for Wheat Yield under Conservation Agriculture and Nitrogen Fertilizer

“…Isotopes of chemical elements are largely used in crop production and land management. Fallout radionuclides ( 137 Cs, 7 Be, and 210 Pb) are used to assess the level and intensity of soil erosion [32][33][34]. The stable isotope 13 C can be used to monitor land degradation [35], as well as water availability [36,37] and soil organic carbon [38][39][40].…”

Microbial Substrate Utilization and Vegetation Shifts in Boreal Forest Floors of Western Canada

“…Stable isotope probing (SIP) of phospholipid fatty acids (PLFAs) found in microbial membranes allows tracking of 13 Clabeled substrates as they become incorporated into soil microbial communities (Waldrop and Firestone, 2004;Watzinger, 2015;Feland and Quideau, 2020). In this study, aspen and spruce forest floors from the mixedwood boreal forest of Alberta were incubated following addition of 13 C-enriched glucose, aspen leaves and aspen roots that had been previously 13 C-labeled, and results were compared to control forest floors (no substrate added).…”