Abstract:

Rainfall is an important factor affecting water supply and soil respiration in wetland areas. Increases in extreme rainfall variability caused by global climate change are thus expected to impact wetland ecosystems. To investigate this, the changes in soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) in response to altered rainfall frequencies (weekly, fortnightly, three-weekly, four-weekly, and control irrigation treatments) were assessed in a wet meadow in the Gahai-Zecha Nature Reserve on the north-eastern edge of the Tibetan Plateau. The SOC was found to increase with increasing rainfall frequency, while TP and TN decreased. SOC and TN decreased with increasing soil depth and TP was inconsistent across the different soil layers. As a result, the ratios of C:P and N:P decreased with the soil layers, but the ratio of C:N did not show a significant change. The ratios of C:N, C:P, and N:P did not show significant responses to the rainfall treatments. The SOC, TN, and TP showed obvious seasonal variations, as the SOC showed an increasing and then decreasing trend, the TN showed a decreasing and then increasing trend, and the TP content showed an “M”-shaped decreasing trend. The results suggest that continuous changes in global rainfall, including an increased rainfall frequency, will aggravate the loss of nitrogen and phosphorus in the shallow soil of the alpine wet meadow, likely resulting in aggravated damage due to eutrophication in the water environment surrounding the alpine wet meadows.

Key words: Qinghai-Tibet Plateau, wet meadows, soil stoichiometric characteristics, rainfall frequency