Integrating Rangeland Health and Stream Stability in Assessments of Rangeland Watersheds

Abstract

Watersheds are distinct hydrologic units that comprise a range of terrestrial upland and riparian complex ecological sites. Since the hydrologic function of the entirety of the watershed is linked, other ecological functions and processes are also likely linked. No single assessment tool is available to describe the ecological status of both terrestrial upland sites and riparian complexes in a single watershed. We investigated the relationship by integrating two assessment tools, Interpreting Indicators of Rangeland Health protocol (IIRH) and stream geomorphic surveys in prairie ecosystems. The qualitative values from the IIRH protocol were different among upland sites associated with 35 intermittent stream reaches in North Dakota in the United States. Riparian complex sites were separated using three metrics of stream stability: stream channel type, bank-height ratio, and Bank Erosion Hazard Index. Stream channel type had the strongest relationship with two attributes of rangeland health, Soil & Site Stability and Hydrologic Function, while bank-height ratio had the strongest relationship with the Biotic Integrity attribute. The influences of individual indicators were identified using a principal components analysis, which revealed unstable streams were typified by departures from the reference state in compaction, soil loss, bare ground, litter dynamics, infiltration, and invasive species. These findings suggest that changes in these IIRH indicators should be monitored and managed by land managers to ensure that riparian function and ecosystem services are not compromised. Future research must continue to investigate the link between upland and riparian functions within a watershed, with special emphasis on vegetation dynamics. In the meantime, integrating these two assessments can provide land managers with vital information about maintaining ecological function throughout the watershed.