Changes of soil organic matter stability along altitudinal gradients in Tibetan alpine grassland
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Background and aims
Changes of soil organic matter (SOM) stability in alpine ecosystems can alter carbon release from the soil and consequently feed back to climate change. We sought to explore the altitudinal patterns of SOM stability and their relationships with climatic, vegetational and edaphic factors.
We combined a number of biological, thermal, chemical, molecular and isotopic indices to characterize SOM stability in two soil layers (0–10 and 10–30 cm) of alpine grassland along two altitudinal gradients of 3200–4200 m (Haibei) and 4400–5200 m (Damxung) on the Tibetan Plateau, respectively.
There were significant altitudinal variations in SOM stability between the two transects. Greater biological, chemical and isotopic indices of SOM stability were observed in the middle altitude in Haibei, while opposite results were observed in Damxung. Except for a decreasing trend of SOM stability along altitudinal gradient in subsurface soils (10–30 cm) in Damxung, there was no significant altitudinal trend of thermal and molecular indices of SOM stability. The multiple indices of SOM stability were mutually associated and all showed greater SOM stability in subsurface soils than in surface soils across regions and altitudes.
Along the altitudinal gradient, SOM stability showed opposite unimodal patterns in Haibei and Damxung, and had higher values in subsurface soils than in surface soils of the alpine grassland. Climatic, vegetational and edaphic factors collectively control SOM stability rather than just temperature or precipitation.
KeywordsAltitudinal gradient Carbon and nitrogen isotopes Molecular composition Soil organic matter stability Soil depth Tibetan Plateau
This study was jointly supported by the National Natural Science Foundation of China (31622013, 31700451 and 31621091). We thank Xiao Chen, Xin Jing, Wen Xiao, Zongju Ding, Mao Tang, and Jiguang Feng for field assistance and laboratory measurement. We also appreciate the constructive comments and suggestions from the editor (Prof. Ingrid Kögel-Knabner) and three anonymous reviewers.
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