RELATIONSHIP OF ALUMINUM AND CALCIUM TO NET CO2 EXCHANGE AMONG DIVERSE SCOTS PINE PROVENANCES UNDER POLLUTION STRESS IN POLAND

Light-saturated net photosynthesis (A(sat)), dark respiration (RD), an d foliar nutrient content of eight European Scots pine (Pinus sylvestr is L.) provenances were measured at experimental sites in western Pola nd. Two-year-old seedlings were planted in 1984 at two sites with simi lar soils in areas of contrasting air pollution. One site was near a p oint source of SO2 and other pollutants, and another 12 km to the sout heast in an area free of acute air pollution was treated as a control. The eight provenances were from a large north-to-south latitudinal ra nge (60 to 43-degrees-N). At the heavily polluted site Scots pine tree s exhibited lower growth rates and crown dieback and deformation. Soil pH, Ca and Mg were at least 10 times lower, and Al 10 times higher at the polluted than the control site. In 1991, concentrations of Al, P, Ca, S, Mn, Fe, and Zn in one-year old Scots pine foliage were higher and Mg lower at the polluted than control site. At both sites foliar M g levels were within the range considered deficient (less-than-or-equa l-to 0.6 mg g-1), and at the polluted site, Al concentrations were ver y high (670 to 880 mug g-1). In all provenances, RD of one-year-old ne edles was higher (by 22% on average) and A(sat) was lower (by 37% on a verage) at the polluted than the control site. The ratio of A(sat): RD was half as great in all provenances at the polluted (4 to 6) than co ntrol site (8 to 11). Provenances of southern origin had greater incre ases in RD and water-use efficiency at the polluted site than other pr ovenances. Within the polluted site alone, or across both sites, A(sat ) in Scots pine was negatively correlated to the Al: Ca ratio (p < 0.0 01, r = -0.93). Across sites RD increased with needle N and Al (multip le regression, p < 0.001). The data suggest that at the polluted site there is excessive soil Al and deficient Mg availability, low needle M g and high Al concentrations and high Al: Ca ratios, and that these ha ve resulted in reduced photosynthetic capacity and increased respirati on.