Response of Soil Organic Carbon and Its Components to Alpine Wetland Degradation in Arid Central Asia

Soil organic carbon (SOC) is composed of carbon components with different stabilities, which is affected by wetland degradation. Understanding the impact of wetland degradation on SOC dynamics provides a basis for the sustainable utilization of wetlands. Here, soils were collected from different degraded areas of the Bayinbuluk alpine wetland—including one non-degraded (ND), one slightly degraded (SD), and one heavily degraded region (HD)—and the effects of degradation on SOC and its components were measured using the sulfuric acid oxidation method (a modified Walkley–Blak method) with different concentrations. The results showed the following: (1) At 0–100 cm of soil, the average total SOC in the ND area was 93.45 g/kg, while that in the SD and HD areas was decreased by 48.7% and 82.0%, respectively. (2) Under ND, SD, and HD, the contents of the very labile OC component (F1) were 29%, 28% and 14%, respectively; those of the labile OC component (F2) were 8%, 8% and 8%, respectively; those of the less labile OC component (F3) were 6%, 7% and 15%, respectively; and those of the recalcitrant OC component (F4) were 57%, 57% and 63%, respectively. (3) There are significant correlations between organic carbon (OC) and its components (p < 0.01), and the proportions of F2, F3, and F4 in SOC are 31%, 7%, 4%, and 58%, respectively. Meanwhile, F4 is the main component in three areas, and the proportion of unstable organic carbon components increases with the aggravation of degradation. Therefore, wetland degradation affects the SOC content and its components, as well as reducing the SOC stability.