While remote sensing has been used extensively and effectively to map burned areas in a wide variety of landscapes, research in this area would benefit from additional work in less frequently investigated cover types such as tallgrass prairie. This is important because various cover types respond differently to fire, and techniques developed for other cover types (e.g., forest, savannah) cannot necessarily be applied to tallgrass prairie.
Doctoral student Rhett Mohler, under the supervision of Professor Doug Goodin in the Department of Geography at Kansas State University, will undertake a research project that will determine the most effective remote sensing tools to use for differentiating burned and unburned prairie grasslands. These tools will also differentiate between burned grasslands other vegetation types. The student will also monitor burned grasslands over one growing season, and finally reconstruct the spatio-temporal fire history of the Flint Hills of Kansas and Oklahoma.
Results of this study will contribute to the broader understanding of burned area mapping by exploring less-studied cover type (tallgrass prairie). Furthermore, this work will address management and societal concerns associated with burning because it will generate information useful for education and training by extension staff and stakeholders. This will ensure that partnerships are built between researchers, extension personnel, and local ranchers - a relationship that is vital if tallgrass prairies are to be managed based on sound scientific knowledge for the benefit of all involved. Finally, this Doctoral Dissertation Research Improvement award will provide support to enable a promising student to establish a strong, independent research career.
North American tallgrass prairie ranks among the finest of all natural grazing lands for large ungulates such as cattle. Fire is a critical management tool in tallgrass prairie. Frequent burning of the prairie canopy selects for a suite of palatable and nutritious grasses, and suppresses the development of woody species that degrade forage quality and reduce the grazing capacity of the prairie. Despite its importance, the extent and frequency of burning in the Kansas Flint Hills (the largest extant tallgrass prairie in North America) is not well known. The objective of our project was to develop a method that uses remotely sensed imagery to map burned areas, then use these methods to develop a retrospective map of burn location and timing over the entire Flint Hills. We achieved several objectives related to mapping burned areas in tallgrass prairie. First, we quantified the efficacy and suitability of remotely sensed measures of surface reflectance for differentiating between burned and unburned surfaces. In addition to several spectral regions, we tested a number of existing indices, all of which rely on detecting the reflectance contrast between intact canopy and canopy removed by fire. Although we used existing methods, application of these methods to mapping burned area in tallgrass prairie is challenging because prescribed burning in the prairie is typically done in early spring, just prior to and during canopy 'greenup.'' Once it begins, this greenup proceeds quite rapidly, thus, any technique for mapping burns much be robust enough to reliably detect the reflectance contrast between burned and unburned canopy against a rapidly changing vegetation background. We found that indices composed of reflectance in the red and near-infrared regions of spectrum were most effective for detecting burned areas. Using what we learned about the efficacy of various spectral bands and indices, we evaluated the effectiveness of both pixel and object-based classification methods for mapping burned areas. We found that the pixel-based classification method was more accurate. We also tested two different satellite-based sensors, Landsat Thematic Mapper and the Moderate Resolution Imaging Spectroradiomter, the latter of which performed best due to its more frequent overpass times. The knowledge gained to this point was then used to identify the best technique for mapping burned areas in tallgrass prairie. We applied this technique in order to map burned areas in the Flint Hills between 2000 and 2010. The resulting burned area maps are valuable to a wide range of stakeholders, including ranchers and landowners, researchers in other academic disciplines such as biology, range management, and climatology, as well as representatives from county, state, and federal government agencies. This information gained from this research has basic scientific value, in that it contributes to the broader body of knowledge about remotely sensed burned area mapping. Specifically, it contributes to both the basic understanding of burn dynamics in tallgrass prairie, as well as to specific burn mapping techniques in prairie, and perhaps in grasslands generally. The development of this technique was also important since, until this time, no method for reliably detecting exactly how much tallgrass prairie is burned each year had been developed. Therefore, by using these burned area maps, the concerns of all stakeholder groups can be addressed and factored into management decisions concerning prescribed burning in the Flint Hills.
