© 1996 Heron Publishing—Victoria, Canada
Root growth and physiology of potted and field-grown trembling aspen exposed to tropospheric ozone
M. D. Coleman (1), R. E. Dickson (1), J. G. Isebrands (1) and D. F. Karnosky (2)
1. USDA Forest Service, North Central Forest Experiment Station, Forestry Sciences Laboratory, 5985 Highway K, Rhinelander, WI
54501, USA / 2. School of Forestry and Wood Products, Michigan Technological University, Houghton, MI 49931, USA / Received March 2, 1995
Summary
We studied root growth and respiration of potted plants and field-grown aspen trees (Populus tremuloides Michx.) exposed to ambient or twice-ambient ozone. Root dry weight of potted plants decreased up to 45% after 12 weeks of
ozone treatment, and root system respiration decreased by 27%. The ozone-induced decrease in root system respiration of potted
plants was more closely correlated with decreased root dry weight than with specific root respiration, suggesting that aspen
root metabolism was less affected by ozone than root growth. We used minirhizotrons to study the appearance and disappearance
of roots in the field. Length of live roots of field-grown trees increased rapidly early in the season and peaked by midseason
in association with a decrease in root production and an increase in root disappearance. In the twice-ambient ozone treatment,
live root lengths were 17% less than those of controls, but the effect was not statistically significant. Seasonal soil CO2 efflux of field-grown trees decreased significantly in the ozone treatments, but because differences in live root length
were not significant and root dry weights were not available, the effect on CO2 efflux could not be attributed directly to decreased root growth.
Keywords:
fine root dynamics, growth respiration, maintenance respiration, Populus tremuloides, root respiration, soil CO2 efflux.
