Understanding the Relationship Between Livestock Disturbance, The Protocols Used to Measure that Disturbance and Stream Conditions

Understanding and managing the effects of livestock grazing on stream systems is of particular concern on federal lands throughout the Interior Columbia River Basin. Land managers monitor three short-term indicators of livestock disturbance (streambank alteration, stubble height, and woody browse) seasonally to ensure livestock grazing does not degrade the long-term health of stream and riparian systems. There are multiple methods for evaluating these indicators; one concern is that different monitoring approaches may have different results. In this research I evaluated three short-term disturbance indicators and compared four different protocols for monitoring streambank alteration at the end of the grazing season. In order for these indicators to be meaningful the methods should be repeatable, related to grazing intensity, representative of cumulative impacts throughout the season, and related to long-term stream conditions. Additionally, it is important that land mangers understand how these indicators respond under different climatic and landscape conditions. In this study I found that the results were dependent on the protocol used and the specific indicator monitored. Measures of streambank alteration and stubble height were moderately repeatable while methods for estimating woody browse were not repeatable. Stubble height and streambank alteration were related to grazing intensity, but the ability to detect alteration at the end of the season was influenced by erosional processes occurring within the grazing season. Streambank alteration was much higher during the drier year of the study because livestock were more dependent of the riparian areas when precipitation was limited. Overall, climatic and geo-physical conditions across the landscape were weakly related to the pattern of disturbance in riparian areas; however, there was higher livestock disturbance in cold arid environments. While the short-term indicators of stubble height and alteration were cumulatively related to long-term stream conditions, the ability to detect changes in individual stream conditions was dependent on the indicator and protocol used. These findings can be used by land managers to make informed decisions about which protocols to use for end-of season disturbance monitoring and will help land managers better understand the relation between short-term indicators and long-term stream conditions