Leveraging long‐term datasets to quantify variability in reference wetland hydrology

Abstract Introduction Wetlands are characterized by hydrology, hydric soils, and hydrophytic vegetation, from which numerous wetland classification schemes have been derived that propose groups of “similar” wetlands. However, trends and variation in long‐term hydrology between and among these classifications remain poorly understood. Objectives Our study aimed to answer three questions: (1) How variable is wetland hydrology between and among different reference wetland types? (2) How are attributes of the ecohydrologic regime related to wetland type? and (3) Which attributes of wetland morphometry (if any) are predictive of wetland ecohydrology across wetland types? Methods We utilized 17 years of bi‐weekly hydrology data from 30 reference wetlands. Hydrologic similarity was assessed using non‐parametric Spearman correlations. Differences in ecohydrologic regimes among wetland types were tested using Kruskal–Wallis and pairwise Wilcoxon rank‐sum tests, principal components analysis, and permutational multivariate analysis of variance (PERMANOVA). To evaluate morphometric controls, we related morphometric attributes (e.g., depth, perimeter:area ratio) to ecohydrologic metrics using redundancy analysis with variance partitioning and stepwise model selection. Results Hydrologic similarity varied widely among wetland types ( r = 0.38 to 0.95). Ecohydrologic regimes showed limited internal consistency, with up to 92% of metrics differing among cypress wetlands and up to 100% of pairwise comparisons differing across all wetland types for magnitude‐based metrics. Wetland depth and perimeter: area ratio emerged as the strongest morphometric predictors of ecohydrologic regime, together explaining 20% of observed variance. Conclusions Wetlands of the same classification often exhibit divergent hydrologic regimes, but simple morphometric attributes improve predictions of ecohydrologic similarity.