LANZHOU, April 22 (Xinhua) -- A new study by Chinese scientists has revealed how cryospheric degradation affects carbon and nitrogen cycles on the Qinghai-Tibet Plateau, providing key data for biogeochemical models of high-altitude cryospheric regions.
The study, spearheaded by the Northwest Institute of Eco-Environment and Resources (NIEER) under the Chinese Academy of Sciences, traces the characteristics and transport mechanisms of dissolved organic matter in the source area of the Yellow River, China's second-longest waterway, on the Qinghai-Tibet Plateau.
Dubbed a core part of the "Asian Water Tower," this glacier- and permafrost-rich region is highly vulnerable to global climate change. As rising temperatures accelerate glacier retreat and permafrost thawing, large amounts of previously sequestered organic matter are being released, disrupting watershed carbon and nitrogen cycles as well as downstream ecological environments.
"It is significant to comprehensively investigate the spatiotemporal characteristics and source composition of the dissolved organic matter in different water bodies in this region," said NIEER researcher Niu Hewen.
Drawing on continuous observations from 2019 to 2022, the team developed a dataset of dissolved organic carbon, dissolved organic nitrogen and dissolved total nitrogen in rainfall, rivers and groundwater.
Their findings revealed that dissolved organic carbon concentrations in the Yellow River's alpine source region are significantly lower than the average for alpine rivers on the Qinghai-Tibet Plateau, with obvious seasonal variations.
Concentrations peak during the summer ablation period, with terrestrial humic-like substances accounting for 72 percent of the source composition. In groundwater, however, microbial protein-like substances dominate, accounting for 82 percent.
The results further showed that the Yellow River source region transports over 100,000 tonnes of dissolved organic carbon downstream annually, with 56 percent concentrated between May and October.
The study indicated that climate warming is accelerating the transformation of cryospheric organic carbon in the source area of the Yellow River from "solid sequestration" to "dynamic output," with significantly enhanced river carbon and nitrogen export, according to Niu.
"The findings of this study not only deepen our understanding of carbon cycling mechanisms on the Qinghai-Tibet Plateau, but also provide a scientific basis for ecological protection, water resource management and climate change response in the Yellow River basin," Niu said. ■
