Characterizing the Turning Points in Ecosystem Functioning and Their Linkages to Drought and Human Activities over the Arid and Semi-Arid Regions of Northern China

Abstract

Identifying the changes in dryland functioning and the drivers of those changes are critical for global ecosystem conservation and sustainability. The arid and semi-arid regions of northern China (ASARNC) are located in a key area of the generally temperate desert of the Eurasian continent, where the ecological conditions have experienced noticeable changes in recent decades. However, it is unclear whether the ecosystem functioning (EF) in this region changed abruptly and how that change was affected by natural and anthropogenic factors. Here, we estimated monthly rain use efficiency (RUE) from MODIS NDVI time series data and investigated the timing and types of turning points (TPs) in EF by the Breaks For Additive Season and Trend (BFAST) family algorithms during 2000–2019. The linkages between the TPs, drought, the frequency of land cover change, and socioeconomic development were examined. The results show that 63.2% of the pixels in the ASARNC region underwent sudden EF changes, of which 26.64% were induced by drought events, while 55.67% were firmly associated with the wetting climate. Wet and dry events were not detected in 17.69% of the TPs, which might have been caused by human activities. TP types and occurrences correlate differently with land cover change frequency, population density, and GDP. The improved EF TP type was correlated with the continuous humid climate and a reduced population density, while the deteriorated EF type coincided with persistent drought and increasing population density. Our research furthers the understanding of how and why TPs of EF occur and provides fundamental data for the conservation, management, and better decision-making concerning dryland ecosystems in China.

Spatial and temporal variation of net primary productivity of herbaceous marshes and its climatic drivers in China

“…The herbaceous marsh vegetation in the northern region of the THS mainly comprises Carex spp., Deyeuxia angustifolia , and Phragmites australis , and the dominant species are Bolboschoenus yagara , Trapa incisa , and Nymphoides peltate in the southern region of this region ( Shen et al., 2021a ). The TAS has high summer and low winter temperatures, with precipitation decreasing from east to west and being unevenly distributed seasonally ( Hong et al., 2022b ) and the dominant species of herbaceous marsh vegetation are Elymus nutans , Suaeda glauca , and Phragmites australis ( Shen et al., 2021a ). Temperatures are high in summer and mid-range in winter in the SH and rainfall is high in both seasons ( Ren et al., 2021 ).…”