Jihyeon Jeon

Spring and autumn, often termed shoulder seasons, represent key transitional phases in Arctic tundra ecosystems, during which nutrient dynamics become highly variable. Biogeochemical cycling during these periods is particularly responsive to warming. Here, we quantify nitrogen uptake and allocation across soil, plant, and microbial fractions in tundra ecosystem at Abisko, northern Sweden, where experimental warming has been maintained for 7 and 17 years, alongside ambient controls. A dual-labeled ¹³C¹⁵N-glycine tracer was used to trace nitrogen incorporation over short-term (24 h) and longer-term (one month) timescales. Isotope recovery across ecosystem pools will be used to determine how warming duration alters the partitioning of nitrogen during seasonal transitions. Based on fieldwork completed last year, this work reports preliminary results from ongoing analyses, with only a limited number of initial findings presented. Once analyses are complete, the results will contribute to improve our understanding of nitrogen dynamics during transition periods under warming in Arctic tundra ecosystems.

Poplar (Populus) clones are widely used for riparian afforestation owing to their fast growth and ecological benefits. However, selecting suitable clones for site-specific conditions remains a key challenge. In this study, we evaluated the survival and growth performance of nine poplar clones belonging to three hybrid groups—Populus deltoides (D), P. deltoides × P. nigra (DN), and P. nigra × P. suaveolens (NS)—at two riparian sites in Korea. Significant differences were observed in the survival, height, diameter, basal area, and basal area increment (BAI) among clones and between sites. DN hybrids exhibited superior overall performance in both survival and growth traits compared to D and NS clones. In the DN group, clones Eco-28, I-476, and Dorskamp consistently ranked highest in aggregate performance. Notably, I-476 and Eco-28 demonstrated both high productivity and stability across sites, as reflected in their low coefficients of variation (CVs). In contrast, Dorskamp, while highly productive, showed relatively high variability across environments. These findings highlight DN hybrids—particularly Eco-28 and I-476—as promising candidates for riparian afforestation, offering a balanced combination of high productivity and environmental stability.

Stable isotopes of water (δ²H and δ¹⁸O) are reliable tracers for the investigation of plant–soil–water interactions in forest ecosystems. However, variations in isotopic compositions may arise due to differences in analytical instruments and water extraction methods. In this study, we conducted three different experiments to identify isotopic differences caused by analytical and methodological variations. First, we analyzed soil water by using the two most commonly applied methods: isotope ratio mass spectrometry (IRMS) and cavity ring-down spectroscopy (CRDS). Second, we compared the isotopes in xylem water extracted from the stems of nine tree species using cryogenic vacuum distillation (CVD) with different heating times. Third, we compared the compositions in xylem water extracted with three different methods: mechanical squeezing using a pressure chamber (PC), an induction module (IM), and CVD. The differences in isotopic composition between IRMS and CRDS were significant but minimal. Soil properties were not significant factors contributing to differences between the two instruments. For the xylem water extraction with CVD, each of the nine tree species required heating for more than three hours. Significant differences were observed in δ²H among the three extraction methods for xylem water. Xylem water extracted by CVD showed more depleted values compared to those obtained by PC and IM. Our results highlight the importance of considering analytical and methodological variations in stable isotope analysis.

Jeong Soo Park, Seung Jin Joo, Jaseok Lee, Dongmin Seo, Hyun Seok Kim, Jihyeon Jeon, Chung Weon Yun, Jeong Eun Lee, Sei-Woong Choi and Jae-Young Lee. J Ecol Environ 2023;47:. https://doi.org/10.5141/jee.23.077

This study investigated the effects of interspecific and temporal variation of specific leaf area (SLA, cm²·g⁻¹) on leaf area index (LAI) estimation for three deciduous broadleaved forests (Gwangneung (GN), Taehwa (TH), and Gariwang (GRW)) in Korea with varying ages and composition of tree species. In fall of 2014, fallen leaves were periodically collected using litter traps and classified by species. LAI was estimated by obtaining SLAs using four calculation methods (A: including both interspecific and temporal variation in SLA; B: species specific mean SLA; C: period-specific mean SLA; and D: overall mean), then multiplying the SLAs by the amount of leaves. SLA varied across different species in all plots, and SLAs of upper canopy species were less than those of lower canopy species. The LAIs calculated using method A, the reference method, were GN 6.09, TH 5.42, and GRW 4.33. LAIs calculated using method B showed a difference of up to 3% from the LAI of method A, but LAIs calculated using methods C and D were overestimated. Therefore, species specific SLA must be considered for precise LAI estimation for broadleaved forests that include multiple species.