The Mississippi River experienced historic flooding during 2019, inducing >150 days of floodplain wetland inundation. We evaluated flood effects using repeated measures of hydrogeomorphic (HGM) wetland assessment variables prior to the flood (October 2018), immediately post-flood (August 2019) and one year after initial assessment (October 2019). The flood had little/no impact on 11 of 13 assessment variables, but altered the abundance of woody debris and forest floor litter. Immediately after the flood, these changes decreased the functional capacity of wetlands to 1) detain floodwater (mean − 9.7% reduction) and 2) precipitation (−17.3%); 3) cycle nutrients (−7.5%); and export organic carbon (−23.8%). Subsequent sampling documented the detain precipitation function returning to pre-flood conditions. The export organic carbon function also improved, yet remained below pre-flood levels. Other functions will likely require additional recovery time due to the persistence of accumulated excess woody debris. Across all sample intervals, floodplain wetlands displayed high wetland function capacities and appear resilient to surface water inundation. This analysis highlights the utility of the HGM assessment to detect responses to changing environmental conditions over short time intervals. The study also emphasizes the need to incorporate metrics with appropriate impact-response characteristics when developing and implementing ecological assessments.

密西西比河在2019年经历了历史性洪水，引发了超过150天的洪泛区湿地淹没。我们在洪水之前（2018年10月），洪水后立即（2019年8月）和初步评估后一年（2019年10月）使用了重复测量的水文地貌（HGM）湿地评估变量来评估洪水影响。洪水对13个评估变量中的11个几乎没有影响，但却改变了木质碎片和森林地垫的数量。洪水发生后，这些变化立即将湿地的功能能力降低为：1）滞留洪水（平均降低-9.7％）和2）降水（-17.3％）；3）循环养分（−7.5％）；并出口有机碳（-23.8％）。随后的采样记录了保持降水功能恢复到洪水前状态。出口有机碳功能也有所改善，但仍低于洪水前水平。由于积聚的多余木屑持续存在，其他功能可能需要更多的恢复时间。在所有采样间隔中，洪泛区湿地显示出较高的湿地功能能力，并且对地表水淹没具有弹性。该分析强调了HGM评估在短时间内检测对变化的环境条件的响应的实用性。该研究还强调，在制定和实施生态评估时，必须将具有适当影响响应特征的指标纳入其中。洪泛区湿地显示出较高的湿地功能能力，并且对地表水淹没具有弹性。该分析强调了HGM评估在短时间内检测对变化的环境条件的响应的实用性。该研究还强调，在制定和实施生态评估时，必须将具有适当影响响应特征的指标纳入其中。洪泛区湿地显示出较高的湿地功能能力，并且对地表水淹没具有弹性。该分析强调了HGM评估在短时间内检测对变化的环境条件的响应的实用性。该研究还强调，在制定和实施生态评估时，必须将具有适当影响响应特征的指标纳入其中。