Effects of Revegetation Approaches on Wetland Plant Community Reassembly Under Hydrologic Extremes

Active revegetation is an integral part of wetland restoration to recover lost ecosystem functions and services in degraded and disturbed sites. However, active revegetation has been pursued less in wetlands compared to other ecosystems and thus, there are few established best practices to guide implementation. Additionally, wetland revegetation is challenging due to dynamic hydrology that is becoming more extreme and high invasive plant propagule pressure that can limit native plant recruitment and favor invasive plant dominance. In this study, we tested the efficacy of varied revegetation approaches on native plant reassembly and invasion resistance in semi-arid wetlands, which are subject to seasonal hydrologic fluctuations. In a Great Salt Lake wetland in Utah, USA, we introduced two functionally distinct native plant mixes, varied their method of introduction via seeding or planting, and varied their order of introduction over two planting dates. Unfortunately, there were no treatment effects on total native or invasive cover, likely due to extreme drought in the first growing season followed by excessive flooding in the second. However, there were compositional shifts from drought-tolerant to flood-tolerant species throughout the study. Community compositional changes underscore the importance of including species with divergent, wide-ranging environmental tolerances in revegetation mixes to enhance native establishment across variable environmental conditions. This bet-hedging approach runs counter to the current focus on precision restoration—the method prioritizing the “right seed in the right place at the right time”—but may be an effective strategy to combat unpredictable site conditions given increasing extreme site conditions.