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19. CHANGE DETECTION OF LEAFY SPURGE (EUPHORBIA ESULA) INFESTATIONS USING AERIAL PHOTOGRAPHY AND GEOGRAPHIC INFORMATION SYSTEMS. G.L. Anderson, C.W. Prosser, S. Hagar, and B. Foster, USDA, ARS, Northern Plains Agricultural Research Laboratory, 1500 N. Central, Sidney, MT 59270 and USDI, Theodore Roosevelt National Park, P.O. Box 7, Medora, ND 58645.
Abstract. Leafy spurge is a troublesome weed on the northern Great Plains of the United States that herbicides and grazing management have not consistently controlled. Remote sensing and geographic information system (GIS) technology have been used to detect and monitor numerous grassland-related problems. The objectives of this study were to use both technologies jointly to map and quantify the extent, distribution, and spatial-temporal dynamics of leafy spurge within Theodore Roosevelt National Park in 1993 and 1998. The five-year comparison provided a unique opportunity to understand how leafy spurge is impacting the park and identify how infestations are changing over time. The same basic methodology was used in 1993 and 1998 with some modifications resulting from improved data handling capabilities. Only the western 8,090 ha of the park were evaluated for both years because of problems with film and cloud contamination encountered in 1998. Data collected in 1998 were not validated prior to this analysis. Preliminary analysis of the data indicated that leafy spurge had doubled during the 5 year period. Leafy spurge extent was estimated to be 591 ha in 1993 and 1,194 ha in 1998. Most infestations were restricted to drainage channels, creek bottoms, and river bottoms. The extent of leafy spurge increased across all aspects and slopes, however, the rate of increase was slower on south facing aspects and flatter slopes. The faster rate of increase on slopes ranging from 6% to 20% indicate that leafy spurge is slowly moving out of the relatively flat drainage channels and butte tops unto steeper slopes. The difference in the rate of increase between the north and south facing aspects combined with the slope and proximate to drainage channel data indicate that water is likely the driving variable for leafy spurge establishment in the Badlands. The most impressive finding of the study was that the extent of leafy spurge appeared to have doubled within 5 years. What makes this finding even more impressive is that the increase was accomplished under an aggressive weed management plan. Managers and administrators charged with the stewardship of federal or state lands and ranchers operating on private land must not delay in managing leafy spurge. Leafy spurge will only be controlled with aggressive and consistent application of integrated pest management tools specifically chosen to meet the individual requirements of each situation.
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