Effects of simulated acid rain on nitrogenase activity (acetylene reduction) in the lichen Stereocaulon paschale (L.) Hoffm., with special reference to nutritional aspects.

Abstract

The effects of SAR (simulated add rain using H2 SO4 and HNO3 singly and combined) on ARA (acetylene reduction activity), and concentrations of N, K4 , Mg2+ and Ca2- was investigated in Sterecaulon paschale (L.) Hoffm. ARA was significantly decreased after 4 months of SAR at pH 3.0. One year after spraying treatments had ceased, lichens treated at pH 3.0. showed no clear signs of recovery of ARA. After 5 y of acidification. ARA in lichens sprayed with combined H2 SO4 and HNO3 at pH 2.9. was comparable to that observed after 4 months of pH 3.0.enhanced rain, i.e. close to zero. SAR at pH 4.0. had no marked effect on nitrogenase activity after 4 months' exposure, but ARA was significantly decreased after 5 y-of pH 4.1. (H2 SO4 ) treatment. There were no clear relationships between the inhibitory effects of acid additions and alterations in nutritional status in the lichen caused by SAR. Furthermore, no correlation between thallus N concentration and nitrogenase activity was observed.