Growth of coniferous trees exposed to SO2 and O3 using an open‐air fumigation system

Abstract

ABSTRACTScots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.) and Sitka spruce (Picea sitchensis Bong. Carr.) were planted as 2‐year‐old seedlings in an open‐air fumigation facility at Liphook in southern England in March 1985. The soil was a humoferric podzol of pH 4. SO2 fumigation began in May 1987 and continued until December 1990. Long‐term mean SO2 concentrations were 4,13 and 22 nmol mo−1. Three plots, one at each SO2 level, were also exposed to O3 at an average of 1–3.times the ambient level. O3 fumigation ran from March to December 1988, May to December 1989 and February to December 1990. Each species reacted differently to treatment. Scots pine showed no growth response to either pollutant, although other work on the site demonstrated a number of deleterious effects of SO2 on this species, including increased leaf loss and foliar injury. Stem basal diameter growth of Norway spruce was depressed in SO2‐treated plots. In contrast, extension growth of shoots of Sitka spruce increased in SO2‐treated plots, in apparent response to codeposition of NH3‐N. However, diameter growth of Sitka spruce main stems did not increase. No effects of O3 on growth were recorded for any species.