【摘要】 冬季土壤呼吸能释放生长季所固存的碳,因而在陆地碳循环中占有重要地位。随着全球气候变暖,平均地表温度将升高0.3–4.8℃,且冬季增温更加明显,而温度的升高会促进更多CO2的释放。另外,滨海湿地地下水位浅,淡咸水交互作用明显,增温能引起土壤表层盐分升高,从而影响土壤呼吸。该研究以黄河三角洲滨海湿地为研究对象,采用红外辐射加热器模拟增温,研究了该地区非生长季土壤呼吸的日动态及季节动态,同时探讨了土壤呼吸对环境因子的响应机制。结果显示:日动态中,增温与对照的土壤呼吸速率变化趋势一致,为单峰曲线;在平均日变化中,整个非生长季不同处理的土壤呼吸速率无显著差异,而土壤温度和土壤盐分均为增温大于对照,并且土壤呼吸峰值时间均比土壤温度提前。季节动态中,整个研究期分为非盐分限制阶段(2014年11月–2015年2月中旬)和盐分限制阶段(2015年2月中旬–2015年4月)。在整个非生长季,土壤呼吸速率无显著差异;在非盐分限制阶段,当10 cm土壤温度升高4.0℃时,土壤呼吸速率显著提高22.9%,而土壤呼吸温度敏感性系数(Q10)与对照相比有所降低;在盐分限制阶段,尽管土壤温度升高3.3℃,土壤呼吸速率却降低了20.7%,这可能是由于增温引起了土壤盐分的升高,同时由增温引起的土壤含水量的升高在一定程度上也限制了土壤呼吸,而此阶段增温对Q10无显著影响。因此,在滨海湿地中,增温除了直接影响土壤温度,还可通过影响土壤水盐状况来影响土壤呼吸,进而影响滨海湿地土壤碳库。更多还原

【Abstract】 Aims Winter soil respiration plays a crucial role in terrestrial carbon cycle, which could lose carbon gained in the growing season. With global warming, the average near-surface air temperatures will rise by 0.3 to 4.8 °C. Winter is expected to be warmer obviously than other seasons. Thus, the elevated temperature can significantly affect soil respiration. The coastal wetland has shallow underground water level and is affected by the fresh water and salt water. Elevated temperature can cause the increase of soil salinity, and as a result high salinity can limit soil respiration. Our objectives were to determine the diurnal and seasonal dynamics of soil respiration in a coastal wetland during the non-growing season, and to explore the responses of soil respiration to environmental factors, especially soil temperature and salinity. Methods A manipulative warming experiment was conducted in a costal wetland in the Yellow River Delta using the infrared heaters. A complete random block design with two treatments, including control and warming, and each treatment was replicated each treatment four times. Soil respiration was measured twice a month duringthe non-growing season by a LI-8100 soil CO2 efflux system. The measurements were taken every 2 h for 24 h at clear days. During each soil respiration measurement, soil environmental parameters were determined simultaneously, including soil temperature, moisture and salinity. Important findings The diurnal variation of soil respiration in the warming plots was closely coupled with that in the control plots, and both exhibited single-peak curves. The daily soil respiration in the warming was higher than that in the control from November 2014 to January 2015. Contrarily, from March to April 2015. During the non-growing seasons, there were no significant differences in the daily mean soil respiration between the two treatments. However, soil temperature and soil salt content in the warming plots were significantly higher than those in the control plots. The non-growing season was divided into the no salt restriction period(November 2014 to middle February 2015) and salt restriction period(middle February 2015 to April 2015). During non-growing season, soil respiration in the warming had no significant difference compared with that in control. During the no salt restriction period, soil respiration in the warming was 22.9%(p < 0.01) greater than the control when soil temperature at 10 cm depth in warming was elevated by 4.0 °C compared with that in control. However, experimental warming decreased temperature sensitivity of soil respiration(Q10). During salt restriction period, soil warming decreased soil respiration by 20.7% compared with the control although with higher temperature(3.3 °C), which may be attributed to the increased soil salt content(Soil electric conductivity increased from 4.4 ds·m–1 to 5.3 ds·m–1). The high water content can limit soil respiration in some extent. In addition, the Q10 value in the warming had no significant difference compared with that in control during this period. Therefore, soil warming can not only increase soil respiration by elevating soil temperature, but also decrease soil respiration by increasing soil salt content due to evaporation, which consequently regulating the soil carbon balance of coastal wetlands.更多还原