Seedling Response to Sulfur, Nitrogen, and Associated Pollutants

摘要

In 1986, the National Acid Precipitation Assessment Program (NAPAP) established the Forest Response Program (FRP) to assess the effects of acidic deposition and associated pollutants on forests. Seedling exposure studies were initiated to determine acute effects of simulated acid deposition, ozone, and sulfur dioxide, and to identify hypothesized mechanisms be which these effects might alter tree condition and hence result in forest decline. From data available as of December 1988, altered post-exposure growth and imbalance in above- and below-ground responses to sulfur dioxide indicated changes in carbon allocation patterns. Simulated acid precipitation reduced frost hardiness of red spruce seedlings at pH 3.0 and led to higher rates of foliar tissue mortality during extreme cold. Loblolly pine showed root and stem growth decreases at ozone levels 80 ppb and higher. Of western conifers, only ponderosa pine showed consistent growth decreases due to ozone.