Ecological Characteristics of Stream Reaches With and Without Low-Tech Process-Based Restoration in a Wildfire-Affected Catchment

Abstract

Low-tech process-based stream restoration (LTPBR) is increasingly implemented following wildfire, underscoring the need to evaluate restoration outcomes in burned catchments. To help address this need, we measured abiotic and biotic characteristics of a reach that received LTPBR, an untreated reach, and a reach with relict beaver activity that had relatively intact berms, all within a catchment that experienced severe wildfire 4 years prior. The relict beaver reach had more shallow, lentic habitat, finer substrate, increased particulate organic matter, greater temperature variability, higher sinuosity, increases in dissolved organic carbon, and decreases in total dissolved nitrogen from above to below the reach. The untreated reach had a deeper, simpler channel, larger substrate, lower particulate organic matter, and more uniform temperatures. The treatment reach had depths, substrate sizes, sinuosity, and temperature variability that were intermediate between the relict beaver and untreated reaches. When scaled to habitat areas at the reach scale, macroinvertebrate biomass was highest at the relict beaver reach and comparable at the treatment and untreated reaches. Standing biomass was highest on wood surfaces. Macroinvertebrate composition differed between habitat types (lotic, lentic, vegetated, wood), but composition, richness, and fluxes into and out of streams did not differ consistently between reaches. The treatment reach had higher brook trout density, the untreated reach had slightly larger fish, and diet composition of trout did not differ across reaches. Taken together, results indicate the restoration treatments had a number of desirable effects, but differed in functioning from more intact beaver berms.