Human‐Induced Changes in Holocene Nitrogen Cycling in North China: An Isotopic Perspective From Sedimentary Pyrogenic Material

Abstract

Abstract Reactive nitrogen (N) deposition from human activity significantly impacts temperate vegetation in areas where low natural N availability limits vegetative productivity. However, the ecosystem response to anthropogenic N deposition remains elusive owing to the scarcity of long‐term empirical observations. Here a N isotope of a pyrogenic material was used to investigate long‐term N availability evolution in a forest‐steppe ecosystem in North China. The N availability was found to have significantly increased since circa 7,400 years BP when primitive agriculture began. Different N availability changes were observed under primitive agriculture (6,600–3,500 cal. years BP) and Sui‐Tang traditional agriculture (AD 581–907), implying dependency on the agricultural mode. A 220‐year N availability recovery period after Sui‐Tang agriculture was observed. On this basis, a minimum of several hundred years is projected for the restoration of the temperate ecosystem if the modern N cascade were to be stopped.