DECOMPOSITION OF BLACKBERRY AND BROOMSEDGE BLUESTEM AS INFLUENCED BY OZONE

Many researchers have reported on individual plant responses to O-3, h ut few have investigated the effects of this pollutant on ecosystem fu nction. Our investigation examined the influence of O-3 on shortterm ( Phase I) litter decomposition of blackberry (Rubus cuneifolus Pursh,) and broomsedge bluestem (Andropogon virginicus L.), two plant species native to early successional forest communities in the southern USA. M ixed blackberry/broomsedge litter (1:1) collected from plants exposed to different levels of O-3 for one growing season was placed in open-t op chambers and exposed to different O-3 levels of treatments for 24 w k. Litter also was incubated in microcosms in the laboratory at 25 or 30 degrees C to determine the effects of climate change on O-3-treated litter. Initial C and N concentrations of the collected foliage did n ot differ significantly among treatments for either species. Blackberr y litter had approximately twice as much N as broomsedge, and when col lected from 2X O-3 chambers, had significantly greater permanganate li gnin than the other treatments. Initial permanganate lignin concentrat ion of blackberry, over all O-3 treatments, correlated significantly w ith remaining mass of the litter mixture after 24 wk exposure. Litter decomposed more slowly in the 2X chambers than in the other treatment chambers, regardless of litter source. Elevated Os-exposed litter (2X) decomposed the slowest regardless of treatment applied. There were si gnificant temperature and time effects observed with litter decomposit ion; litter incubated at 30 degrees C decomposed faster than at 25 deg rees C. Our data suggest O-3 may influence substrate quality and micro bial activity, thus reducing the rate of litter decomposition in early successional forest communities.