Data from 25 experiments on seedlings of 43 tree species and hybrids show that ozone (0,) can reduce growth and photosynthesis at concentrations common in many areas of the USA. Seedlings have been primarily employed for such studies for logislic reasons, and will likely provide the greatest breadth of information for some time IO come. However, a number of impediments limit application of seedling response studies IO assessment of impacts on regional timber production. Large trees differ from seedlings in a number of ways, including C allocation and canopy structure, and methods must be developed IO acrount for these differences if information from seedling studies is to prove useful IO forest impact assessmenl.Understanding how competition mediates individual tree responses will require investigation of whether systematic differences of microclimate leaf morphology that exist across canopies affects foliage sensitivity IO 0,. and whether the maximum growth rates of genolypes are correlated with susceptibility IO 0,. Definitive information on these factors is necessary IO assess imparts of 0, on stand development and diameter distributions in both mulli-and single species stands. Of critical economic importance is whether 0, preferentially damages taller, more valuable individuals within stands and more valuable, faster growing stand types.

We estimate a wildfire risk model with a new measure of wildfire output, intensity-weighted risk and use it in Monte Carlo simulations to estimate welfare changes from alternative prescribed burning policies. Using Volusia County, Florida as a case study, an annual prescribed burning rate of 13% of all forest lands maximizes net welfare; ignoring the effects on wildfire intensity may underestimate optimal rates of prescribed burning. Our estimated supply function for prescribed fire services is inelastic, suggesting that increasing contract prescribed fire services on public lands may produce rapidly escalating costs for private landowners and unintended distributional and “leakage” effects. Copyright 2007, Oxford University Press.