Hydrologic Regimes Revealed Bundles and Tradeoffs Among Six Wetland Services

Ecosystem services are often described as occurring together in bundles, or tending not to occur together, representing tradeoffs. We investigated patterns and potential linkages in the provision of six wetland services in three experimental wetlands by measuring: flow attenuation, as peak flow reduction; stormwater retention, as outflow volume reduction; net primary productivity (NPP), as plant biomass; diversity support, as plant species richness; erosion resistance, as stability of surface soils in a flow path; and water quality improvement, as nutrient and sediment removal. Levels of ecosystem services differed in our system because of differences in hydrologic regime brought on by natural variation in clay-rich subsoils. The fastest-draining wetland (with thin clay layer) provided five of six services at their highest level, but had lowest NPP. In contrast, a ponded wetland (with thick clay layer) that was dominated by cattail (Typha spp.) provided the highest level of NPP, but lowest levels of all other services. Hence, in our site, drainage supported several bundled services, whereas ponding supported such high levels of NPP that other services appeared to be limited (suggesting tradeoffs). These outcomes show that high NPP has the potential to be a misleading indicator of overall ecosystem services. Rather than focusing on NPP, we suggest identifying and establishing hydrologic regimes that can support the services targeted for restoration in future projects. Further direct assessments of multiple services are needed to identify bundles and tradeoffs and provide guidance at the scale of local restoration projects.