Structural characteristics of late-successional pine-hardwood forest following recent infestation by southern pine beetle in the Georgia Piedmont, USA

At Murder Creek Research Natural Area, Georgia, USA, we compared structural characteristics of late-successional pine-hardwood stands two to three yea rs after infestation by southern pine beetle (Dendroctonus frontalis Zimmer man) to those of adjacent noninfested stands. Death of up to eight Pinus ta eda L. and P. echinata Mill. per mortality patch reduced stem density of pi nes from 399 to 205 trees ha(-1). Stand basal area and average diameter of pines in beetle-infested stands (9.0 m(2) ha(-1) and 26.9 cm, respectively) were less than those of noninfested stands (30.6 m(2) ha(-1) and 38.5 cm, respectively). Stand basal area of hardwoods in southern pine beetle-infest ed stands (9.1 m(2) ha(-1)) was less than that of noninfested stands (14.5 m(2) ha(-1)) primarily because of lower abundances of Liquidambar styracifl ua L. and Acer barbatum Michx. However, tree species diversity in beetle-in fested stands exceeded that of noninfested stands (Simpson's indices of 0.6 9 and 0.55, respectively) because proportionate abundance of hardwoods (67% and 33% of total stand basal area, respectively) was increased by the deat h of pines. Results indicate that small patch mortality from southern pine beetle increased structural complexity of late-successional pine-hardwood s tands by causing localized reductions in stem density of large pines (and t herefore reduced susceptibility to future beetle attacks) and associated in creases in tree species diversity. Development of several old-growth charac teristics, particularly increased abundance of snags and dominance by late- successional hardwood species, has been accelerated by southern pine beetle infestation.