| The importance of landscape-level connectivity to depressional wetland structure function is ambiguous. The ambiguity is a result of the relative significance researchers have placed on surface versus groundwater hydrology. Depressional wetlands are often characterized by small, closed basins without a naturally integrated surface drainage system. Water inputs are dominated by surface runoff. In contrast, variation in vegetation structure is often attributed to differences in wetland permanence, and salinity, both of which are reportedly driven by deep (>4 m) groundwater connections among wetlands. In opposition to both views, I compared differences in depressional wetland structure and function between wetlands with and without a temporary (<4 wk) surface water or near-surface water (<1 m) connection to an adjacent up-gradient wetland. “Connected” wetlands had greater mean wetland/catchment ratios, but stored more water, stored water longer, had higher specific conductance, and were more productive than “isolated” wetlands. Wetland plant composition of “connected wetlands” was different than that of “isolated” wetlands. I compared local hydrology, water chemistry, and soil development between groundwater discharge and non-discharge locations within wetlands and found no evidence of groundwater inputs. My results provide evidence that depressional wetland hydrology and vegetation structure are primarily determined by surface and near-surface hydrologic processes that are expressed at both the landscape and localized spatial scales. Conservation policies should incorporate depressional wetland dependence on landscape-level hydrologic processes, specifically their commonly ignored surface and near-surface hydrologic connections. |
