Preferential use of root litter compared to leaf litter by beech seedlings and soil microorganisms

International audienceBackground and aims Litter decomposition is regulated by e. g. substrate quality and environmental factors, particularly water availability. The partitioning of nutrients released from litter between vegetation and soil microorganisms may, therefore, be affected by changing climate. This study aimed to elucidate the impact of litter type and drought on the fate of litter-derived N in beech seedlings and soil microbes. Methods We quantified N-15 recovery rates in plant and soil N pools by adding N-15-labelled leaf and/or root litter under controlled conditions. Results Root litter was favoured over leaf litter for N acquisition by beech seedlings and soil microorganisms. Drought reduced N-15 recovery from litter in seedlings thereby affecting root N nutrition. N-15 accumulated in seedlings in different sinks depending on litter type. Conclusions Root turnover appears to influence (a) N availability in the soil for plants and soil microbes and (b) N acquisition and retention despite a presumably extremely dynamic turnover of microbial biomass. Compared to soil microorganisms, beech seedlings represent a very minor short-term N sink, despite a potentially high N residence time. Furthermore, soil microbes constitute a significant N pool that can be released in the long term and, thus, may become available for N nutrition of plants