BUILT FOR DISTURBANCE: LIMITED VEGETATION RESPONSES TO LOW-TECH PROCESS-BASED RESTORATION IN NORTHERN COLORADO FLOODPLAINS

Abstract

Channel incision is a major driving factor of change in floodplain vegetation communities and is a common outcome in burned watersheds. Low-Tech Process-Based Restoration (LTPBR) methods aim to reconnect channels with their floodplains to restore channel-floodplain connectivity and ecosystem functions such as periodic overbank flooding. However, short-term floodplain vegetation responses to LTPBR remain poorly understood despite the growing popularity of these treatments. We evaluated whether LTPBR increased floodplain inundation, and whether increased flooding led to increased productivity and promoted wetland plant communities. We monitored peak-season flooding extent, sediment deposition, plant community composition and productivity across treated and untreated reaches of variable burn severity. LTPBR increased early-season overbank flooding but did not retain surface water into late-summer. Vegetation composition and productivity remained largely unchanged, although sediment deposits created microsites colonized by clonal graminoids and early successional species. These results suggest that short-term hydrologic changes were insufficient to trigger broad vegetation shifts, likely because disturbance thresholds necessary for community reassembly were not met and community change occurs over longer timescales. Restoration outcomes following LTPBR may depend on sustained, periodic hydrologic disturbance over multiple years to drive floodplain vegetation change.