02469nas a2200241   4500008004100000245011700041210006900158300001300227490000600240520165700246653000901903653002101912653001201933653002501945653002201970653002001992653001402012653002202026100001502048700001902063700001802082856012702100       2002                        eng d00aAssessing the rate, mechanism and consequences of conversion of tallgrass prairie to Juniperus virginiana forest0 aAssessing the rate mechanism and consequences of conversion of t  a578 -5860 v53 aWe assessed the determinants and consequences of the expansion of Juniperus virginiana L. (red cedar) populations into central US grasslands using historical aerial photos and field measurements of forest extent, tree growth, fire-induced mortality, and responses in herbaceous species diversity and productivity. Photos from northeast Kansas dating back to 1956 indicate that native tallgrass prairie can be converted to closed-canopy red cedar forest in as little as 40 years (a 2.3% increase in forest cover per year). Mean tree density in 21 forested sites ranged from 130 to 3500 trees/ha, with most sites at more than 800 trees/ha. In younger stands, maximum growth rates of individual red cedar trees exceeded 20 cm/y in height. Land management practices were critical to the establishment and growth of red cedar forest. Grazing reduced the fuel loads by more than 30% in tallgrass prairie. Based on measurements of mortality for more than 1800 red cedar trees, fire-induced mortality in grazed areas averaged 31.6% versus more than 90% at ungrazed sites. When tallgrass prairie was converted to red cedar forest, herbaceous species diversity and productivity were drastically reduced, and most grassland species were virtually eliminated. Consequently, community structure shifted from dominance by herbaceous C4 species to evergreen woody C3 species; this shift is likely to be accompanied by alterations in carbon storage and other ecosystem processes in a relatively short time period. Here we present a conceptual model that integrates the ecological and socioeconomic factors that underlie the conversion of grassland to red cedar forest.10afire10aforest expansion10aGrazing10aJuniperus virginiana10aland-cover change10aland-use change10ared cedar10atallgrass prairie1 aHoch, G.A.1 aBriggs, J., M.1 aJohnson, L.C.  uhttp://knz.lternet.edu/content/assessing-rate-mechanism-and-consequences-conversion-tallgrass-prairie-juniperus-virginiana