Title

Different responses of sedimentary delta N-15 to climatic changes and anthropogenic impacts in lakes across the Eastern margin of the Tibetan Plateau

Authors

Xu, H; Yu, KK; Lan, JH; Sheng, EG; Liu, B; Ye, YD ; Hong, B; Wu, HX; Zhou, KG; Yeager, KM

Abstract

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 centennialimulti-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 delta N-15 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.

Corresponding author

Xu Hai

Volume

123

Issue

Page

111-118

Pub year

June, 2016

Publication name

Journal of Asian Earth Sciences

Details

http://www.sciencedirect.com/science/article/pii/S1367912016300700