An inverse relationship between moisture and grazing intensity in an arid mountain-basin system

Abstract

Precipitation has been suggested as a crucial influencing factor in the primary productivity in arid and semi-arid regions, yet how moisture fluctuation in an arid mountain-basin system of the north Qinghai–Tibetan Plateau has affected human activities is poorly understood. Here, we reconstruct the variations of grazing intensity in high elevations and regional humidity based on independent and high-resolution records of Sporormiella-type coprophilous fungal spores and pollen grains in the same well-dated sediment core from Lake Tian’E in the western Qilian Mountains over the past 3500 years. We find that stronger grazing activity was associated with low regional effective moisture, and propose that the drier regional climate pushed people and their livestock into the mountainous areas. A notable exception was a reduction of human and grazing activities in arid region with high mountains during 380–580 CE caused by centennial-length dry and cold conditions. In addition, it is also noteworthy that intensified grazing activity occurred during 580–720 CE and after ∼1920 CE, corresponding to a warmer and wetter climate and diverse subsistence strategies with social developments in the lowlands of the Hexi Corridor. Our findings potentially provide a historical reference for understanding how ancient people adapted to the climate change in arid region with high mountains.