Reviews and syntheses: How do abiotic and biotic processes respond to climatic variations in the Nam Co catchment (Tibetan Plateau)?

• Published in: Biogeosciences Vol. 17; no. 5; pp. 1261 - 1279
• Main Authors: Anslan, Sten, Azizi Rad, Mina, Buckel, Johannes, Echeverria Galindo, Paula, Kai, Jinlei, Kang, Wengang, Keys, Laura, Maurischat, Philipp, Nieberding, Felix, Reinosch, Eike, Tang, Handuo, Tran, Tuong Vi, Wang, Yuyang, Schwalb, Antje
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 06.03.2020; Copernicus Publications
• Subjects: Abiotic factors; Air temperature; Availability; Biodegradation; Biodiversity; Carbon; Carbon dioxide; Carbon dioxide flux; Carbon emissions; Case studies; Catchment area; Catchment areas; Catchments; Climate change; Climate variations; Closed lakes; Deglaciation; Diatoms; Dissolved organic matter; Emissions; Emissions (Pollution); Environmental changes; Fluxes; Freshwater; Geodiversity; Glacier melting; Glaciers; Global climate; Global temperature changes; Global warming; Global warming effects; Grasslands; Grazing; Inland water environment; Lakes; Livestock; Livestock grazing; Meltwater; Mineral nutrients; Mountain environments; Nutrient availability; Nutrients; Plateaus; Pleistocene; Pollution control; Reviews; Sediments; Sediments (Geology); Tracking; Translocation; Water availability; Water chemistry; Water levels; Tibetan Plateau
• ISSN: 1726-4189; 1726-4170; 1726-4189
• DOI: 10.5194/bg-17-1261-2020

The Tibetan Plateau (TP) is the largest alpine plateau on Earth and plays an important role in global climate dynamics. On the TP, climate change is happening particularly fast, with an increase in air temperature twice the global average. The particular sensitivity of this high mountain environment allows observation and tracking of abiotic and biotic feedback mechanisms. Closed lake systems, such as Nam Co on the central TP, represent important natural laboratories for tracking past and recent climatic changes, as well as geobiological processes and interactions within their respective catchments. This review gives an interdisciplinary overview of past and modern environmental changes using Nam Co as a case study. In the catchment area, ongoing rise in air temperature forces glaciers to melt, contributing to a rise in lake level and changes in water chemistry. Some studies base their conclusions on inconsistent glacier inventories, but an ever-increasing deglaciation and thus higher water availability have persisted over the last few decades. Increasing water availability causes translocation of sediments, nutrients and dissolved organic matter to the lake, as well as higher carbon emissions to the atmosphere. The intensity of grazing has an additional and significant effect on CO2 fluxes, with moderate grazing enhancing belowground allocation of carbon while adversely affecting the C sink potential through reduction of above-surface and subsurface biomass at higher grazing intensities. Furthermore, increasing pressure from human activities and livestock grazing are enhancing grassland degradation processes, thus shaping biodiversity patterns in the lake and catchment. The environmental signal provided by taxon-specific analysis (e.g., diatoms and ostracods) in Nam Co revealed profound climatic fluctuations between warmer–cooler and wetter–drier periods since the late Pleistocene and an increasing input of freshwater and nutrients from the catchment in recent years. Based on the reviewed literature, we outline perspectives to further understand the effects of global warming on geodiversity and biodiversity and their interplay at Nam Co, which acts as a case study for potentially TP-level or even worldwide processes that are currently shaping high mountain areas.