Riverine solute versus discharge (C–Q) relationships provide information about the magnitude and dynamics of material fluxes from landscapes. We analysed long‐term patterns of C–Q relationships for 44 rivers in Florida across a suite of geogenic, nutrient, and organic solutes and investigated land cover, watershed size, and surficial geology as controls on these patterns. Solute concentrations generally exhibited far less variability than did discharge, with coherent solute‐specific behaviours repeated across watersheds. Geogenic solutes generally diluted with increasing discharge, whereas organic solutes generally enriched; patterns for nutrients were highly variable across watersheds, but on average exhibited chemostasis. Despite strong evidence of both geologic and land cover controls on solute flow‐weighted concentrations, these variables were poor predictors of C–Q slopes (β) or relative coefficients of variation (CVC:CVQ). CVC:CVQ generally increased with watershed size, and wetland area appeared to influence C–Q patterns for base cations and organic solutes. Perhaps most importantly, we observed significant slope breaks in C–Q association in approximately half of our observations, challenging the generality of using single power functions to describe catchment solute export patterns. For all solutes except phosphorus (P), C–Q slopes decreased above statistically identified breaks (slopes for P increased), with breaks consistently at or near median flow (i.e., 50% flow exceedance probability). This common pattern significantly impacts solute load estimates; failing to account for slope breaks overestimates nitrate and total organic carbon loads as much as 125% and underestimates P loads as much as 35%. In addition to challenging generic power‐law characterization of C–Q relationships for these coastal plain rivers, and exploring the load estimate consequences thereof, our study supports emerging insights about watershed hydrochemical behaviours across a wide array of solutes.

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Abstract. Wetland microtopography is a visually striking feature, but also critically influences biogeochemical processes at both the scale of its observation (10−2–102 m2) and at aggregate scales (102–104 m2). However, relatively little is known about how wetland microtopography develops or the factors influencing its structure and pattern. Growing research across different ecosystems suggests that reinforcing processes may be common between plants and their environment, resulting in self-organized patch features, like hummocks. Here, we used landscape ecology metrics and diagnostics to evaluate the plausibility of plant–environment feedback mechanisms in the maintenance of wetland microtopography. We used terrestrial laser scanning (TLS) to quantify the sizing and spatial distribution of hummocks in 10 black ash (Fraxinus nigra Marshall) wetlands in northern Minnesota, USA. We observed clear elevation bimodality in our wettest sites, indicating microsite divergence into two states: elevated hummocks and low elevation hollows. We coupled the TLS dataset to a 3-year water level record and soil-depth measurements, and showed that hummock height (mean = 0.31±0.06 m) variability is largely predicted by mean water level depth (R2=0.8 at the site scale, R2=0.12–0.56 at the hummock scale), with little influence of subsurface microtopography on surface microtopography. Hummocks at wetter sites exhibited regular spatial patterning (i.e., regular spacing of ca. 1.5 m, 25 %–30 % further apart than expected by chance) in contrast to the more random spatial arrangements of hummocks at drier sites. Hummock size distributions (perimeters, areas, and volumes) were lognormal, with a characteristic patch area of approximately 1 m2 across sites. Hummocks increase the effective soil surface area for redox gradients and exchange interfaces in black ash wetlands by up to 32 %, and influence surface water dynamics through modulation of specific yield by up to 30 %. Taken together, the data support the hypothesis that vegetation develops and maintains hummocks in response to anaerobic stresses from saturated soils, with a potential for a microtopographic signature of life.

Depressional wetlands are dominant features in many low‐gradient landscapes, where they provide water storage and exchange. Typical basin morphology enables water storage during drier periods, when surface flow paths are disconnected and exchange is limited to slower groundwater flow paths. Under wetter conditions, wetland stage can exceed surface connection thresholds, activating surface flow paths to downstream waters. Empirical methods are needed to quantify these dynamics and thus to assess their role in landscape hydrology and associated functions. We developed a new water budget‐based approach to enumerate connectivity thresholds and flows from stage measurements. We propose that this approach, termed Connectivity and Flow from Stage (CFS), has broad applicability across wetlandscapes. We applied the CFS method in the Big Cypress National Preserve, where we hypothesized that surface connectivity episodes control water and solute flux, with consequences for exported carbonate weathering products and thus for karst landform evolution. Across five study wetlands, this analysis detected surface connectivity thresholds and assessed temporal flow dynamics. Imputed connectivity thresholds were clear from stage‐dependent net flow dynamics and aligned well with LiDAR‐derived thresholds. Water export occurred overwhelmingly when stage exceeded these thresholds, indicating that water and solute export from these wetlands is dominated by periods of enhanced landscape connectivity. Notably, the presented CFS method can quantify wetland connectivity thresholds from stage data, even without supporting geomorphic information. This approach is useful for understanding hydrologic controls on biogeomorphic evolution in this particular karst landscape, and more broadly for inferring wetland connectivity patterns and magnitudes in other wetlandscape settings.

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