Knowledge of historical variations in sedimentary δ15N values and their relation to modern ones in lakes is critical in understanding N cycling in inland aquatic systems. Here we present late Holocene sedimentary δ15N variations in four lakes across the Eastern margin of the Tibetan Plateau (ETP), namely Lake Qinghai and Lake Chaonaqiu over north ETP (N-ETP) area, and Lake Yihai and Lake Lugu over south ETP (S-ETP) area. The results show that: (1) during historical periods when anthropogenic forcing was weak, the centennial/multi-decadal changes in δ15N values were dominated by climatic changes. Higher precipitation brought greater nutrients supply and led to higher Lacustrine Primary Productivity (LPP) and higher δ15N values in lake sediments, and vice versa. (2) During the recent/modern epoch with enhanced anthropogenic impacts, sedimentary δ15N values in Lake Qinghai and Lake Chaonaqiu (mid-high latitude lakes with low LPP) showed decreasing trends, possibly related to the increased global atmospheric reactive nitrogen (Nr) deposition. On the contrary, sedimentary δ15N values in Lake Lugu and Lake Yihai (subtropical lakes with high LPP) showed increasing trends, most likely because more dissolved inorganic nitrogen in lake water was used during LPP processes. This study highlights that LPP plays an important role in modifying sedimentary δ15N values both for historical and modern times, whereas atmospheric Nr deposition seems to influence the modern/recent sedimentary δ15N trends in lakes with low LPP.
|Number of pages||8|
|Journal||Journal of Asian Earth Sciences|
|State||Published - Jun 1 2016|
Bibliographical noteFunding Information:
This work was funded by the Natural Science Foundation of China (No.: 41473120 ) and the National Basic Research Program of China (No.: 2013CB955903 ).
© 2016 Elsevier Ltd.
- Atmospheric nitrogen deposition
- Lacustrine primary productivity (LPP)
- Lake sediment
- Nitrogen isotopes
- Tibetan plateau
ASJC Scopus subject areas
- Earth-Surface Processes