Response of Greenhouse Gas Fluxes to Simulated Precipitation and Related Environmental Factors in the Qinghai Lake Lakeside Wetland

To clarify the effects of precipitation changes on greenhouse gas (CO2, CH4, N2O) emissions from the lakeshore wetland ecosystem of Qinghai Lake, this study establishes five precipitation treatments (D25%, D75%, CK, I25%, I75%) using a rainfall manipulation device. During the growing season, greenhouse gas fluxes were measured via the static chamber–gas chromatography method, while soil temperature, moisture, total carbon (TC), total nitrogen (TN), pH, electrical conductivity (EC), and aboveground and belowground biomass were simultaneously monitored. The results showed that at 11:00, both increased and decreased precipitation inhibited CO2 and CH4 emissions (with D25 showing the strongest inhibition for CO2 and I75 for CH4); however, increased precipitation promoted N2O emissions (I75 strongest), while decreased precipitation suppressed them (D25 strongest). At 15:00, only D25 inhibited CO2 emissions, whereas all other treatments promoted them (I75 strongest). CH4 fluxes under all treatments were higher than those in CK, indicating a promoting effect (I25 strongest). N2O emissions responded to precipitation changes as follows: wetting promoted emissions (I25 optimal), while drying suppressed them (D75 stronger). Correlation analyses revealed treatment- and time-specific patterns. At 11:00, significant negative correlations between CO2 and soil temperature and significant positive correlations between CH4 and soil temperature were observed only under I75; soil moisture was significantly positively correlated with CH4 under D25; TN significantly inhibited all three gases under wetting treatments; and TC showed a highly significant negative correlation with N2O under I75 (p < 0.01). At 15:00, soil temperature generally promoted CO2 and CH4 emissions (except for CO2 under D75); soil moisture promoted CH4; TC was negatively correlated with both CO2 and N2O; pH was positively correlated with CO2 only under CK; the correlation between EC and CO2 shifted from positive (CK) to negative (I75); aboveground biomass suppressed CO2 under I25 and I75 but promoted N2O under D25. In summary, precipitation changes significantly modulate greenhouse gas emissions and their relationships with soil factors, with strong temporal and treatment dependencies. Future studies should integrate long-term observations and process-based models to further quantify the comprehensive effects of precipitation changes on the greenhouse gas budget of this wetland ecosystem.