Acid fog effects on conifer seedlings : Air Pollution and Forest Decline. 14th International Meeting for Specialists in Air Pollution Effects on Forest Ecosystems

1989

S. 125-129

4 Abb., 1 Tab., 19 Lit. Ang., En, Zfsg. En

Unselbständiges Werk

200034658

Experiments were performed to assess the effects of acid fog on foliar injury, biomass production, and nutrient leaching in selected conifers. One- year od seedlings of Pseudotsuga menziesii, Pinus ponderosa, Tsuga heterophylla und Thuja plicata were exposed episodically to fog events of variable duration (22 events over a 60 day period for a total of 93 hr). Exposures occurred in open top chembers with fog acidified to pHs of 2.1, 3.1 or 5.6 Foliar injury was ovserved only in T. heterophylla (pH 2.1 and 3.1) and T. plicata (pH 2.1). The low pH fog treatments significantly reduced root biomass in T. heterophylla and across speies there was a trend towards a reduced proportion of total dry weight as roots with decreasing fog pH. A concurrent experiment examined foliar leaching in P. menziesii. Seedlings were grown in solution culture at two levels of nutrient availability and exposed to pH 5.6 or pH 3.1 fog (24 events over an 84 day period for a total of 96 hr). For seedlings at the higher level of nutrient availability, foliar leaching rates were determined by analyses of throughfall olutions and compared to root uptake rates (based on depletion from the nutrient solutions). Fog pH did not affect total biomass production or foliar nutrient contents. However, plant growth and foliar nutrient levels were higher in plants grown at the higher nutrient level. Foiar leaching (K > Ca > Mg) was greater with a pH 3.1 fog than a pH 5.6 fog but the amounts leached (by a 4 hour pH 3.1 fog) were small compared to the daily uptake rates for these seedlings.