Detecting the Influence of Best Management Practices on Vegetation Near Ephemeral Streams With Landsat Data

Various best management practices (BMPs) have been implemented on rangelands with the goals of controlling nonpoint sourcepollution, reducing the impact of livestock in ecologically important riparian areas, and improving grazing distribution.Providing off-stream water sources to livestock in pastures, cross-fencing, and rotational grazing are common rangeland BMPsthat have demonstrated success in drawing livestock grazing pressure away from streams. We evaluated the effects of rangelandBMP implementation with six commercial-scale pastures in the northern mixed-grass prairie. Four pastures received a BMPsuite consisting of off-stream water, cross-fencing, and deferred-rotation grazing, and two pastures did not receive BMPs. Wehypothesized that the BMPs increased the quantity of riparian vegetation cover relative to the conditions in these pasturesduring the pre-BMP period and to the two pastures that did not receive BMPs. We used a series of 30-m Landsat normalizeddifference vegetation index (NDVI) images to track the spatial and temporal changes (1984–2010,n¼24) in vegetation cover, towhich NDVI has been well correlated. Validation indicated that the remotely sensed signal from in-channel vegetation wasrepresentative of ground conditions. The BMP suite was associated with a 15% increase in the in-channel NDVI (0–30 m fromstream centerline) and 18% increase in the riparian NDVI (30–180 m from stream center line). Conversely, the in-channel andriparian NDVI of non-BMP pastures declined 30% and 18% over the study period. The majority of change occurred within 2 yrof BMP implementation. The patterns of in-channel NDVI among pastures suggested that BMP implementation likely alteredgrazing distribution by decreasing the preferential use of riparian and in-channel areas. We demonstrated that satellite imagerytime series are useful in retrospectively evaluating the efficacy of conservation practices, providing critical information to guideadaptive management and decision makers