降雨量改变对黄河三角洲滨海湿地土壤呼吸的影响

全球变化背景下,降雨模式变化造成土壤水分波动是引起土壤呼吸动态变化的重要驱动力。但滨海湿地如何响应降雨模式变化,进而引起生态系统蓝碳功能改变的机制尚不清楚。依托黄河三角洲滨海湿地增减雨野外控制试验平台,采用土壤碳通量观测系统(LI—8100)对湿地土壤呼吸速率进行监测,探究了2017年黄河三角洲滨海湿地土壤呼吸及环境、生物因子对减雨60%、减雨40%、对照60%、对照40%、增雨40%、增雨60%等变化的响应及机制。结果表明:1)随着降雨量增加,湿地土壤温度逐渐降低;同时增雨和减雨处理均显著提高了湿地土壤湿度(P0.05)。(2)降雨量变化显著影响湿地植被物种组成、地上和地下生物量分配以及植被根冠比(P0.05)。增雨40%和增雨60%均显著提高了湿地植物种类和植被根冠比,但同时显著降低了湿地植被地上生物量。此外,增雨40%和减雨60%处理均显著提高了湿地植被地下生物量。(3)降雨量变化对2017年湿地季节土壤呼吸无显著影响,但在湿地非淹水期,增雨60%和增雨40%均显著提高了湿地土壤呼吸速率(P0.05)。(4)2017年湿地不同降雨处理的土壤呼吸与土壤湿度均呈二次曲线关系(P0.05),相关系数随降雨量增加而降低;同时在非淹水期不同降雨处理的土壤呼吸与土壤温度均指数相关(P0.05),土壤呼吸温度敏感性(Q_(10))随降雨量增加而增大。在淹水期不同降雨处理土壤呼吸与土壤温度无显著相关关系。(5)淹水期土壤呼吸速率与地表水位呈指数负相关(P0.001)。

Effects of changes in precipitation on soil respiration in coastal wetlands of the Yellow River Delta

Soil moisture fluctuation caused by changes in precipitation patterns associated with global change is an important driving force for the dynamic changes of soil respiration. However, it is unclear how coastal wetlands respond to changes in precipitation patterns, and thus cause changes in the ecosystem blue carbon function. To explore the response and mechanism of soil respiration and environmental and biological factors to precipitation changes, the soil carbon flux observation system was applied to monitor wetland soil respiration rates under different precipitation treatments relying on increased and decreased precipitation fields outside the control experiment platform of the Yellow River Delta coastal wetland in 2017. The results showed that: (1) with increased precipitation, the wetland soil temperature gradually decreased; simultaneously, both precipitation increase and decrease significantly increased wetland soil moisture (P < 0.05); (2) changes in precipitation significantly affected vegetation species composition, aboveground and belowground biomass allocation, and root/shoot ratio (P < 0.05). A 40% and 60% precipitation increase significantly increased the wetland plant species and vegetation root shoot ratio; however, it significantly reduced the aboveground biomass of wetland vegetation. In addition, a 40% increase and 60% decrease of precipitation significantly increased the aboveground biomass of wetland vegetation; (3) there was no significant effect of precipitation changes on annual soil respiration in wetlands. Nevertheless, a 60% and 40% precipitation increase both significantly increased the soil respiration rate in wetlands during the non-flooding season (P < 0.05); (4) the wetland soil respiration and moisture showed a quadratic curve (P < 0.05) with the correlation coefficient decreasing with precipitation increase. Furthermore, during the wetland non-flooding season, soil respiration and temperature were exponentially correlated (P < 0.05) with soil temperature sensitivity (Q₁₀) increasing with increasing precipitation. There was no significant correlation between soil respiration and temperature during flooding periods; (5) during the flooding period, the soil respiration rate was inversely correlated with the surface water level (P < 0.001).