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This discussion understates the effect of acid deposition on forest vegetation. While it may be arguable that the vast majority of the south is not significantly affected at present, it is clear from the situation in the high Appalachians that this issue is of critical importance in that region. The implications of the "high degree of uncertainty about the direction and magnitude of forest impacts from projected climate changes" also should be discussed. -- Draft Report
We do highlight concern for the effects of acid deposition in the Southern Appalachians in both the Summary Report and in chapter HLTH-3. -- Final Report
Decreases in the ozone exposure will lead to increased growth from some pines depending on the forest type. The Draft SAMI report on ozone effects to forest trees presents this relevant finding after using the TREGRO and Zelig models. Between 1995 and 2010 loblolly pine is expected to increase in basal area by about 25% for two forest types in two ozone regions (see Figure 3 in comment letter) and by 2040 increase by 55% in the loblolly-hardwood type in the Sipsey ozone region (see Figure 4 supplied in comment letter). Therefore, SAMI results indicate that loblolly pine, in stands mixed with hardwoods, are likely to increase in basal area because the stress caused by ozone will be reduced and loblolly pine will be able to outcompete neighboring tree species. -- Draft Report
This conclusion assumes that the scenario in the previous comment (40-3) is true. See above comment. -- Final Report
The second conclusion (Ozone pollution is forecast to increase..."): It is true that a warmer climate could lead to increased ozone formation due to warmer and sunnier days needed for ozone formation. Furthermore, high doses of ozone can result in the reduction in the amount of fine root formation and make trees more susceptible to drought. These assumptions may be valid if nitrogen oxides are expected to increase, but as discussed previously, most likely nitrogen oxide emissions will decrease in the future. Certainly an anticipated increase in ozone (exposure) of 20 to 50 percent by 2025 will not occur and the cumulative ozone exposures (Figure 2, supplied in comment letter #40) and peak concentrations are expected to decrease at low elevation and high elevation sites in the SAMI domain. The assumption that NOx concentrations will decrease in the future is the critical assumption here. The SAMI integrated assessment shows NOx concentrations as remaining stable between 1990 and 2010 and then declining slightly by 2040. According to the document, shifts in NOx sources will occur primarily in the utilities and highway sectors such that decreases in utility-driven NOx production will more than offset major predicted increases in highway emissions, thus lowering overall atmospheric NOx concentrations. No further information is given in the document regarding how these numbers are derived. The SAMI document says: "SAMI will qualitatively evaluate the uncertainty for inventory projections, and where possible, quantify the range of uncertainty for specific emissions categories or source sectors of the projection inventories." (from http://www.saminet.org/ia/emissions.html). Also, it does not appear that these numbers have been peer-reviewed. Based on these conclusions, it seems a bit hasty to assume that ozone concentrations will be lower in the future (based on projected NOx reductions); especially if summer temperatures and human densities continue to rise in the region. -- Draft Report
This conclusion assumes that the scenario in the previous comment (40-3) is true. See above comment. -- Final Report
The statement "many southern forests are fire adapted" is vague and not provable through time with research nor is there sufficient empirical evidence to support this claim. Please be more specific with a number or percentage, and locate these forest types. The statement "increases in ozone will reduce growth" leaves out the logical conclusion that harvests will go down from the existing forecasts on both public and private forestlands. -- Draft Report
We've added specific information regarding fire regimes to the Summary Report from the Background Paper on Fire. -- Final Report
The first conclusion "While effects are variable..." The conclusion states that nitrate deposition is expected to have a greater impact to terrestrial and aquatic systems than sulfate deposition. The SAMI analysis indicates nitrogen deposition is expected to decrease throughout most of the region; furthermore, sulfates will continue to play a significant role in base cation depletion due to mountainous soils retaining deposited sulfates and then releasing the sulfates in the future. -- Draft Report
We state in chapter HLTH-3 that both nitrogen and sulfur deposition are expected to change terrestrial and aquatic ecosystems. However, the degree of change is an ongoing research priority of the Southern Appalachian Mountain Initiative. -- Final Report
In the first finding "While the effects are variable...": It appears there is an assumption that nitrogen oxides are expected to increase. Figure 1 (supplied in comment letter #40) shows the estimated nitrogen oxide reductions throughout the eight SAMI states, which correspond to a large portion of the SFRA. The three values to examine in the figure are the base, A2 in 2010 and A2 in 2040. The base case represents total estimated nitrogen oxide emissions for the 8 states, while the A2 emissions represent current laws, rules, and regulations that are being implemented. Clearly it can be seen that nitrogen oxide emissions are expected to decrease in the future.(See comment letter #40 for data.) -- Draft Report
Throughout chapter HLTH-3, we state that nitrogen oxide concentrations are expected to decrease. However, these new concentrations are still expected to have negative impacts on forests across the South. -- Final Report
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created: 4-OCT-2002 |