水位变化对湿地土壤CO_(2)排放速率的影响研究

Effect of Water Level Change on CO_(2)Emission Rate from Wetland Soils

为研究水位变化幅度和周期对土壤CO_(2)排放速率的影响,采集黄河小北干流区原状土样进行为期1161 h的室内水位控制监测试验,分高水位波动(a)、低水位波动(b)、干旱胁迫(c)和参照组(d)4组进行对比,分析5个阶段的CO_(2)排放速率、DOC(可溶性有机碳)和DOC/DON(可溶性有机氮)数据。在监测全过程中CO_(2)排放速率平均值分别为0.23、0.22、0.16、0.22μmol/(cm2·h),水位变化整体造成0.35倍、-0.18倍、-0.11倍、-0.24倍的改变。相较于监测过程的平均值,水位变化造成a、b、c、d 4组-0.72~2.48倍、-0.86~1.18倍、-0.97~1.44倍、-0.85~0.70倍的过程性波动,CO_(2)排放速率表现出“上升—衰弱—恢复”的特征。相较于前一阶段平均值数据,水位下降后(阶段Ⅰ)a、b、c 3组发生2.48、1.18、1.44倍的上升,持续时间91.5 h后又发生0.18、0.43和0.27倍的下降(阶段Ⅰf);监测279.9 h时的水位上升造成a、b、c 3组较前一阶段明显上升(阶段Ⅱ),48.5 h后a、b、c 3组排放速率下降(阶段Ⅱf);664 h时的水位上升(阶段Ⅲ、Ⅲf)造成的影响类似于前一阶段,在监测最后的240 h内(阶段Ⅳ),4组较Ⅲf阶段都有不同程度的回升。0~5 cm和5~10 cm土壤DOC含量和DOC/DON值受水位变化影响明显,出现初期上升和后期下降的趋势。水位变化对湿地土壤CO_(2)排放表现出大幅度、长时间的影响,水位变化对湿地土壤CO_(2)排放速率影响显著且具有阶段性特征。

To study the effect of water level variation amplitude and period on soil CO_(2)emission rate,undisturbed soil samples were collected from the Xiaobei main stream of the Yellow River for 1161h long-term water level control monitoring.4 groups were divided into high water level fluctuations(a),low water level fluctuations(b),drought stress(c),and reference group(d)for comparison.CO_(2)emission rate,dissolved organic carbon(DOC),and DOC/DON(dissolved organic nitrogen)data from five stages were analyzed.The average CO_(2)emission rates throughout the monitoring process are 0.23,0.22,0.16,and 0.22μmol·cm-2·h-1 respectively,the overall change in water level causes changes of 0.35 times,-0.18 times,-0.11 times,and-0.24 times.Compared to the average value of the monitoring process,water level changes cause process fluctuations of-0.72~2.48 times,-0.86~1.18 times,-0.97~1.44 times and-0.85~0.70 times in groups a,b,c,and d,respectively CO_(2)emission rate exhibited a characteristic of"rising-weakening-recovering".Compared to the average data of the previous stage,after the water level drops(Stage I),the abc group suggested 2.48,1.18 and 1.44 times increase,and after 91.5 hours,there were 0.18,0.43 and 0.27 times decrease(Stage If);The water level rise at 279.9 hours of monitoring caused a significant increase in the abc group compared to their previous stage(Stage II)while decreased after 48.5 hours(Stage IIf);The impact of the water level rise at 664 hours(stages III and III f)is similar to the previous stage.In the last 240 hours(stage IV),all 4 groups showed varying degrees of rebound compared to stage III.DOC content and DOC/DON value in soil between 0~5 cm and 5~10 cm were significantly affected by changes in water level,showing a trend of initial increase and later decrease.Water level changes have a significant and long-term impact on wetland soil CO_(2)emissions,and the impact is significant and has a phased characteristic.