Research progress on isotope labeling in plant-soil-microbe interactions: A case study of forest ecosystem nutrient cycling

In the study of nutrient cycling in forest ecosystems, traditional methods are increasingly unable to meet the researchers need for understanding the mechanisms of nutrient cycling. Stable hydrogen and oxygen isotope tracing techniques have become important methods for studying the mechanisms of nutrient cycling in forest ecosystems due to their high sensitivity and tracing capabilities. Scholars from both domestic and international backgrounds have conducted research on nutrient cycling in forest ecosystems from various time scales and hierarchical levels. Based on a brief introduction of the principles of hydrogen and oxygen isotope tracing, this paper systematically elaborates on the use of stable 15N isotope dilution techniques and tracing techniques to determine the conversion rate of total N in forest soils and the 15N recovery rate. This aims to reveal the transport and transformation laws and retention mechanisms of forest soil 15N, especially inorganic N. By utilizing stable isotope tracing, isotope ratio mass spectrometry analysis, and other techniques, research on biological nitrogen fixation has been conducted, including the measurement of biological nitrogen fixation, the study of nitrogen fixation mechanisms, and the identification of new nitrogen-fixing species. Isotope labeling, as a key technical means for exploring the biological world, can trace chemical reactions within microbial organisms and their influencing factors. It aims to lay a scientific foundation for further exploration of nutrient cycling in forest ecosystems, especially processes related to nitrogen cycling. Additionally, it provides basic data and theoretical basis for the protection, restoration, and sustainable management of forest ecosystems.