Impacts of low-tech restoration methods on soil, vegetation, and livestock grazing in Montana's sagebrush steppe

Abstract

In the semi-arid rangelands of western North America, water is a limiting factor for plant growth. In Montana's high elevation rangelands, snowmelt is the primary source of water for ephemeral streams and mesic meadows. Wildlife and livestock rely on these areas especially when surrounding uplands have dried. Less snowpack and early melt times associated with climate change pose a threat to forage resources in this region. In 2018 and 2019, small rock restoration structures were constructed in seven drainages in southwest Montana with the intention of increasing resiliency in these systems. In this study we compare stream reaches with restoration structures to reaches without structures to assess the impacts of this technique on soil moisture, plant cover, diversity, evenness, and production. We observed cattle grazing within and adjacent to treated drainages to determine how they use the landscape. We used soil moisture probes to measure soil water content once per month in June-September of 2021 and 2022. We used 0.5m2 frames to estimate plant cover, diversity, and evenness June-September in both years. At the end of each growing season, vegetation frames were clipped and weighed to estimate production. Soil and vegetation sampling occurred in 54 reaches across 7 drainages. We observed cattle near four treated drainages in mornings and evenings to assess whether cattle prefer mesic or upland areas. Cattle observations occurred in July and August of 2021 and 2022. Using linear fixed effects models, we detected no differences (p > or = 0.05) in soil moisture between treated and untreated reaches during any sampling period. We detected no differences in vegetation cover, richness, diversity, or evenness in 92% of sampling periods. No differences in plant production were detected in 2021 or 2022. Cattle used mesic areas in greater proportion to their abundance on the landscape in both years (p < or = 0.0001). Our results indicate that these structures have not yet had major impacts on soil moisture or vegetation metrics. However, our results indicate that mesic meadows are an important resource for grazing cattle in southwest Montana's high- elevation rangelands, supporting the idea that these areas warrant restoration efforts.