Sr. Shafer et al., ANALYSIS OF OZONE CONCENTRATION - BIOMASS RESPONSE RELATIONSHIPS AMONG OPEN-POLLINATED FAMILIES OF LOBLOLLY-PINE, Canadian journal of forest research, 23(4), 1993, pp. 706-715
Tropospheric ozone may contribute to the reported growth decline of pi
nes in the southeastern United States. Ozone concentration - response
relationships were quantified for open-pollinated families of loblolly
pine (Pinus taeda L.) seedlings. Seedlings from 30 families were expo
sed to ozone (0, 80, 160, 240, or 320 nL 03/L air) in greenhouse chamb
ers for 6 h per day, 4 days per week, for 12 weeks. Top (shoot) and ro
ot biomass were determined for each of 900 plants. Twelve families wer
e selected for a subsequent experiment to examine consistency of resul
ts (360 plants). For each response variable, statistical models consis
ting of fixed and random effects were based on combined data for all f
amilies and both experiments. Data were fit to both polynomial and Wei
bull model types. The maximum suppression of any biomass variable (top
, root, or total dry weight) predicted by a regression model for plant
s exposed for 12 weeks to 320 nL/L was 25% for total dry weight (Weibu
ll model based on data representing all 42 family-year combinations, t
otal of 1260 plants). Families were ranked for sensitivity based on es
timates of a single parameter from the models, and model type had no e
ffect on the order of sensitivity rankings of the 42 family-experiment
combinations. The same families represented die extremes in sensitivi
ty among the 12 families that were exposed in both experiments.