SHIFTS IN BOTANICAL COMPOSITION OF FLATWOODS RANGE FOLLOWING FERTILIZATION

Three annual applications of a factorial combination of N (0, 40, 80, 120 kg ha(-1)), P (0, 25 kg ha(-1)) and K (0, 100 kg ha(-1)) were appl ied to Florida flatwoods range where 45 plant species were initially p resent, Addition of P and K had no effect (P>0,05) on indices of plant diversity, density, or above-ground biomass, Both Shannon's (Y = 1.6 - 0.005N, where N is kg ha(-1)) and Simpson's index (Y = 0.28 + 0,002N ) indicated diversity decreased with increasing N because the communit y was being dominated by goldenrods (Solidago fistulosa and Euthamia m inor) and dogfennel (Eupatorium spp,). Density of all forbs increased with increasing N (1990 plants m(-2) = 17.4 + 0,4N and 1991 plants m(- 2) = 35.1 + 1,4N), Density of beaked panicum (Panicum rhizomatum) incr eased quadratically with increasing N,while density of decumbent carpe tgrasses (Axonopus spp,) and low panicums (Dichanthelium spp,) decline d linearly, Broomsedge (Andropogon virginicus), wiregrass (Aristida st ricta), and bottlebrush 3-awn (A, spiciformis) were eliminated from th e site, Above-ground biomass of forbs increased with N (1988 kg ha(-1) = 934 + 16,1N and 1990 kg ha(-1) = 227 + 60,6N), Grass and grasslike biomass increased linearly as N increased, but N effects were independ ent of year, which were different (1988 = 1,530 kg ha(-1) and 1990 - 2 ,140 kg ha(-1)). The plant community at this location became less dive rse when the naturally low soil N was increased by 40 kg ha(-1) or mor e, Early successional species replaced later successional species, esp ecially creeping bluestem (Schizachyrium scoparium).