| dc.description.abstract | The influence of "acid rain" (watering with tap water acidified to
pH 3.0 ) and drought on jack pine seedlings and balsam poplar cuttings
growing in two different soil types was studied in a short-term greenhouse
experiment. Changes in soil chemistry were assessed and a number of
growth parameters and physiological processes measured.
Irrigation with "acid rain" led to rapid soil acidification. It resulted
in decreased soil pH, cation exchange capacity and base saturation, and
altered concentrations of the basic exchangeable ions; the level of Al’”
increased, while the levels of Ca*', Mg”and K’ decreased. There was a slight
decrease in total soil organic matter and a slight increase in soil nitrogen.
Drought generally enhanced the adverse effects of the soil acidification
process.
“Acid rain" had a beneficial effect on seedling and cutting growth and
development. Height and diameter growth, development of root surface area,
production of aboveground and belowground biomass were stimulated by
"rain" with pH 3.0. Seedlings and cuttings watered with "acid rain" also had
lower water saturation deficit, lower diffusive resistance and higher
transpiration rates. Changes in leaf chlorophyll fluorescence indicated
slight stimulation of photosynthesis. Drought reduced seedling and cutting
growth and development, but "rain" with pH 3.0 significantly reduced these
adverse effects. Both tree species responded in a similar way to the stress
factors. Plants performed better in the lighter soil because of better
growth conditions. For early tree growth and development, "acid rain" was
not directly harmful even when combined with drought. | |
