isotope ratio in beech but not in the other tree species. The results of this study showed that it is possible to infer the type and timing of processes relevant to N resorption by analyzing leaf δ 15 N variation during senescence.

Stable isotopes provide a powerful means of elucidating the trophic ecology of organisms. Analyses of variation in the ratio of nitrogen isotopes (d 15 N) can provide insights into the trophic position of species with broad diets and the ability to occupy multiple positions in food webs, such as ants. The most powerful studies compare subjects across various spatial scales, but to do so, local variation in d 15 N baselines must be taken into account. To date, a wide variety of baseline calibration methods have been employed, leading some authors to suggest that a standard approach is needed, and that the reality of environmental variation necessitates that this should be at fine scales. In this study, we examine the fine-scale variation in d 15 N value of colonies of the ant Formica kozlovi Dlussky (Hymenoptera: Formicidae: Formicini) along a sloped transect in Mongolia, and compare these with values for associated soils in an effort to shed further light on this issue. We find variation in ant d 15 N to the order of one trophic level (ca. 3&), over a distance of only 1 km. Ant d 15 N was highly correlated with soil d 15 N, and variation in mineral soil d 15 N explained ca. 81% of the variation in ant d 15 N. This study underlines the importance of local-scale baseline corrections for isotopic studies, particularly in environments where baseline variation might be expected. It further suggests that d 15 N of mineral soils may provide a suitable baseline for ecological studies of terrestrial arthropods.

Background and Motivation: Nitrogen content in tissues of Fagus crenata Blume is key for flowering and seed production. However, there is a lack of information on seasonal intra-plant nitrogen partitioning in this representative tree species typical of heavy snowfall regions in Japan. Therefore, the objective of this study was to elucidate Fagus crenata intra-plant nitrogen movement by means of nitrogen content, nitrogen isotope analysis, and amino acids temporal variability. Materials and Methods: Nitrogen content, isotope ratio, and free amino acids content were measured in coarse roots, sapwood, leaves, and litter in four phenological stages in nine adult Fagus crenata trees and upscaled to the whole-tree level.

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Background and aims Soil carbon sequestration can play an important role in mitigating climate change. Higher organic C inputs to agricultural soils are needed in order to increase soil organic carbon (SOC) stocks. Genotype selection and breeding towards increased root biomass may enhance root C inputs to the soil and could therefore be a promising, easy-to-implement management option for potentially increasing C sequestration. However, an increase in root C inputs may compromise yield, which is not desirable in terms of food security. Methods Data from 13 global studies with field experiments were compiled in order to estimate the potential of optimised genotype selection for enhancing root biomass without compromising the yield of winter wheat, spring wheat, silage maize, winter rapeseed and sunflower. A lack of data on the effect of variety on rhizodeposition was identified which thus had to be excluded. Results Systematic genotype selection increased mean yields by 52% and mean root biomass by 22% across all crops and sites. A median root C increase of 6.7% for spring wheat, 6.8% for winter rapeseed, 12.2% for silage maize, 21.6% for winter wheat and 26.4% for sunflower would be possible without a yield reduction. Conclusion Overall, this review demonstrates that optimised genotype selection can be a win-win option for increasing root biomass C input to soil while maintaining or even enhancing yield.