No abstract

Decomposition, nutrient, and isotopic (δ(13)C and δ(15)N) dynamics during 1 year were studied for leaf and twig litters of Pinus densiflora, Castanea crenata, Erigeron annuus, and Miscanthus sinensis growing on a highly weathered soil with constrained nutrient supply using litterbags in a cool temperate region of South Korea. Decay constant (k/year) ranged from 0.58 to 1.29/year, and mass loss ranged from 22.36 to 58.43 % among litter types. The results demonstrate that mass loss and nutrient dynamics of decomposing litter were influenced by the seasonality of mineralization and immobilization processes. In general, most nutrients exhibited alternate phases of rapid mineralization followed by gradual immobilization, except K, which was released throughout the field incubation. At the end of study, among all the nutrients only N and P showed net immobilization. Mobility of different nutrients from decomposing litter as the percentage of initial litter nutrient concentration was in the order of K > Mg > Ca > N ≈ P. The δ(13)C (0.32-6.70 ‰) and δ(15)N (0.74-3.90 ‰) values of residual litters showed nonlinear increase and decrease, respectively compared to initial isotopic values during decomposition. Litter of different functional types and chemical quality converged toward a conservative nutrient use strategy through mechanisms of slow decomposition and slow nutrient mobilization. Our results indicate that litter quality and season, are the most important regulators of litter decomposition in these forests. The results revealed significant relationships between litter decomposition rates and N, C:N ratio and P, and seasonality (temperature). These results and the convergence of different litters towards conservative nutrient use in these nutrient constrained ecosystems imply optimization of litter management because litter removal can have cascading effects on litter decomposition and nutrient availability in these systems.

The geographical origin of agricultural products has been intensively studied, but links between agricultural products and the environments are poorly established. Soils, water (streamwater and groundwater), and plants (hot pepper, Capsicum annuum; and rice, Oryza sativa) were collected from all regions of South Korea and measured Sr isotope ratios ((87)Sr/(86)Sr). Sequential leaching of soil showed that Sr in the exchangeable and carbonate fractions (bioavailable) had a lower (87)Sr/(86)Sr ratio than that in the silicate fraction, consistent with a low (87)Sr/(86)Sr ratio in the plant. Although the bedrock-soil-water-plant system is closely linked, statistical analysis indicated that (87)Sr/(86)Sr ratios of the plant showed the greatest agreement with those of water and the exchangeable fraction of soil. This study is the first report of (87)Sr/(86)Sr isoscapes in South Korea and first demonstrates that the agricultural product is strongly linked with the exchangeable fraction of soil and water.