Spatially different responses of nitrogen processing to precipitation during glacial-interglacial cycles on the Chinese Loess Plateau.

Abstract Terrestrial nitrogen (N) cycling is closely associated with precipitation and crucial to ecosystem, which has been receiving great concerns at the backdrop of global climate change. In addition to modern investigations, paleo record of N cycling may provide valuable clues about how ecosystem N responds to climate change. Here we measured soil organic nitrogen (TON) and its isotope value (δ15N org) in two loess-paleosol sequences (LPS), i.e. the Yuanbao (YB) and Luochuan (LC) sequences, on the Chinese Loess Plateau (CLP) accumulated during the glacial-interglacial cycles. Both sequences showed higher magnetic susceptibility in paleosol and lower in loess, but with overall higher values in the wetter site of LC, suggesting higher precipitation during warm periods for both sites, as well as higher precipitation at site LC than at site YB. TON increased with increase of paleo-precipitation in both sequences, but the fraction of microbial derived ON, estimated from (C/N) org , increased faster than plant-derived ON at site YB but slower at site LC. δ15N org was used to estimate microbial mediated gaseous N loss, showing greater losses at higher paleo-precipitation at site YB and a reverse trend at site LC. Thereby, both (C/N) org and δ15N org suggest a quicker response of microbes than plants to precipitation at the drier site YB but conversely at the wetter site LC. Such a spatially different responses of nitrogen processing to precipitation would be a reference for projection of future terrestrial ecosystem response to climate change. Graphical abstract Unlabelled Image Highlights • Two loess-paleosol profiles on the Chinese Loess Plateau were studied. • The C/N and δ15N of soil total organic matter change regularly with precipitation. • Microbes and plants respond differently to precipitation due to competition for N. • The records are beneficial to predict N loss in future climate change. [ABSTRACT FROM AUTHOR]