Ecological responses to meadow restoration in the sagebrush steppe of Montana

Abstract

In the semi-arid landscapes of the Western United States, water is scarce. In the high-elevation sagebrush steppe of Southwest Montana, mesic meadows are primarily fed by melting snowpack. These meadows, often centered around an ephemeral stream, collect and store water in the soil. Between 60-80% of wildlife rely on meadows for resources when surrounding upland environments are dry. Warming temperatures and declining snowpack are threatening water resources in this region. Stream incision, often induced by historic land use, decreases water storage in surrounding meadows. In 2018 and 2019, rock restoration structures, typically less than 0.3 m tall, were installed in seven impaired catchments in Southwest Montana to mitigate climate change and incision by slowing and spreading water. Catchments spanned an ecological and abiotic gradient that accounts for over 1/3 of the variation within the sagebrush biome. We compared reaches with structures built to reaches without to assess the impact of restoration on average soil moisture, soil drying rate, water storage, water retention time after rainfall events, and sage-grouse chick food resources (plants and arthropods). We installed soil moisture probes at 24 reaches in 4 catchments, recording hourly measurements from June through September in 2020, 2021, and 2022. Using 0.5 m 2 frames, we estimated vegetation canopy cover at the species level once per month in June through September. We set 24 hr pitfall traps once per month from June through August. Vegetation and arthropod sampling occurred in 2021 and 2022 at 54 reaches in 7 catchments. We detected an increase in water residence time at treated reaches of 1.67 days (p=0.0069) after controlling for variation between catchments and reaches. We also found evidence for a 27% increase in total canopy cover (p=0.004) at treated reaches when compared to control reaches. We found no evidence of a difference in seasonal soil moisture, seasonal drying rate, seasonal water storage, arthropod activity density, or arthropod biomass. Our results indicate that rock restoration structures are effective in increasing soil moisture and vegetation components in mesic meadows in Southwest Montana, potentially providing a tool to restore meadows in semi-arid landscapes and build resilience against climate change.