The importance of past and recent land use policies in woody plant expansion in Eastern Kansas
Within North American tallgrass prairie, changes in the timing, intensity and frequency of fire have been implicated as important proximate drivers of grassland-to-shrubland/woodland transitions. The replacement of native grasses by shrubs or trees results in loss of biodiversity and habitat for grassland species, and directly impacts regional livestock production. Historically, prescribed fire was used to maintain rangelands in eastern Kansas, but recently use of fire in these grasslands has become controversial.
We focus on patterns of woody plant expansion at the Konza Prairie Biological Station (KPBS) in NE Kansas and in the surrounding Flint Hills region. Historical surveys of woody vegetation taken in 1859 were coupled with a 63-year record of aerial photographs to document riparian forest expansion at KPBS. 30+ years of plant cover data in experimental fire (1,2,4 and 20 fire return intervals) and grazing (grazed by Bos bison or ungrazed) treatments was used to quantify change in woody plant cover in areas that were historically grass-dominated. We used remote sensing to determine the expansion of eastern red cedar (Juniper virginiana) in the surrounding region. We then link these results with social science findings from several sets of semi-structured, open-ended interviews about environmental change with regional experts and local land managers.
While only 5 ha of forest was recorded on KPBS in 1859, areal cover of riparian forest has increased to > 300 ha. At a plot level, cover of woody plants has increased across all fire treatments with the largest increases in areas burned at a low fire frequency. Documented increases in woody vegetation in the surrounding Northern Flint Hills were also linked to reduced fire frequency associated with land-use change, especially growth in human populations and residential development. Interviews with local experts indicated that periodic fire was viewed as both a supporting ecosystem service that maintains these grasslands, and a cultural service with ribbons of fire slowly moving across the landscape providing aesthetic value. Concerns related to air quality in downwind urban areas has increased the need for additional outreach/education concerning the role of fire in maintaining the ecosystem services of the tallgrass prairie. With urban centers growing and more individuals unfamiliar with the role of fire in rangelands, the future of tallgrass prairie is uncertain.