Predicting Variation in Springtime Wetland Occurrence and Flooded Area in Nebraska's Rainwater Basin
Migratory waterbirds rely on stopover habitat along migration routes to replenish energy reserves and improve body condition. Shallow, closed-basin playa wetlands in the Rainwater Basin region of south-central Nebraska provide critical stopover habitat for migratory waterbirds in the Central Flyway. The ephemeral nature of these wetlands and localization of precipitation events influences the distribution and degree of springtime wetland ponding and causes avian stopover habitat to vary among locations and years. Ponding is hypothesized to be driven by weather events, individual wetland characteristics, and surrounding landuse; but it is unclear which variables, or combinations of them, are most important.
We used generalized linear mixed models and linear mixed models in a multi-model inference framework to compare alternative hypotheses explaining wetland inundation (presence/absence of water) and ponded area in 2004 and 2006 â 2009. Candidate variables included local weather events, surrounding landuse, and wetland characteristics. In general, surrounding rowcrop agriculture, greater hydric footprint shape complexity, and warmer and drier weather patterns negatively influence wetland inundation and ponded area. The degree of ponding in Rainwater Basin wetlands was greater in 2007 than 2006, presumably because 2006 was relatively dry and 2007 was relatively wet. Differences between these and other years are reflected in inundation model predictions for individual years.
Validations of predictive models were conducted with a subset of regional wetlands not used for model training, and validation results show the inundation model to be a better predictor of wetland inundation than the ponded area model is of wetland ponded area. Models may be used to inform the managers of publicly owned wetlands regarding the use of groundwater pumping to provide additional stopover habitat, and identify and prioritize wetland and watershed restoration actions in this highly altered agricultural landscape.