Quantifying the direct effects of SO2 and O3 on forest growth

Abstract

The direct effects of sulphur dioxide (S0 2 ) and ozone (0 3 ) on the growth of two Douglas-fir stands are quantified from continuous measurements of the concentration of air pollution above the canopy combined with a quantitative description of the direct effects of gaseous uptake of pollutants on photosynthesis and respiration. Effects at the leafleve1 are scaled up to the stand level, using a deterministic model of forest growth that uses time steps of 1 day. This approach enables total uptake of gaseous air pollutants and their effects on canopy assimilation and growth to be quantified, taking ambient weather conditions and stand structure into account. By using a description of water balance in the model, the influence of limitations in soil moisture availability can also be incorporated, and the combined effects of air pollution and water shortage can be accounted for. Under Dutch conditions, with average daily concentrations of 10 Jlg m-3 for S0 2 and 50 Jlg m-3 for 0 3 , the short-term effects on tree growth appear to be minor, except near local sources, and during episodes of high concentrations under stable weather conditions. The possible magnitude oflong-term effects of exposure to 0 3 is assessed using a hypothetical relationship between dose (exposure multiplied by duration) and foliage loss. From this it is concluded that long-term effects may be significant in stands with a low leaf area index.

Did the Ambient Ozone Affect Stem Increment of Scots Pines (Pinus sylvestrisL.) on Territories under Regional Pollution Load? Step III of Lithuanian Studies

“…Therefore, this procedure allowed the elimination of the impact of air concentration of acidifying compounds and their deposition on BAI, and verified strong interaction of acid compounds with crown defoliation that was detected not only in our earlier studies, but also in the cause-effect studies on pine defoliation changes in Europe [38]. In our opinion, elimination of the defoliation impact on tree increment was a good example of an attempt to separate the effects of different pollutants [30], i.e., acidifying compounds and ambient O 3 by empirical regression methods.…”

Effects of irrigation and balanced fertilization on nutrient cycling in a Douglas fir stand

“…However, a strong evidence for the improved soil conditions is found in the growth figures. In the roof plot trees actually reached potential growth, which is 25.1 Mg h a -l y-1 or 35 m 3 h a -1 y -1 according to model calculations on carbon assimilation (Mohren et al, 1992).…”

“…Height measurements (H in m) were done each year on 50 -100% of the trees in each treatment with an extendable pole. Stem volum~ increment (V in L) was calculated from Branch, needle and root biomass were estimated from DBH using biometric data of Mohren et al (1992). The annual element uptake was estimated from growth increments of tree compartments and their chemical composition.…”

“…Fine root biomass was not included in the estimate, because their turnover occurred within one year (Olsthoorn and Tiktak, 1991). Needle biomass increment was assumed to be 400 kg ha-l higher than average needle fall, according to model calculations (Mohren et al, 1992) and irrespective of treatment. Branch increment was fixed at 2 Mg ha-1 y -l , as was derived from Evers et al (1991)• In the last treatment year Leaf area index (LAI) was measured with a LICOR device in all plots.…”

Rebuttal of ARCO's reports on phytotoxicity (Redente) & vegetation (Keammerer) /

“…Photosynthesis can also be reduced due to toxic build-ups of sulfite within plant tissues, but effect is reversible as long as the rate of build-up does not exceed the plant's capacity to detoxify it (Mohren et al, 1992). Holland et al (1995) noted that abnormal shoot extension growth in SO2 fumigated Picea sitchensis (Sitka spruce) trees returned to normal the year after fumigation ceased.…”