© 2001 Heron Publishing—Victoria, Canada
Seasonal changes in above- and belowground carbohydrate concentrations of ponderosa pine along a pollution gradient
Nancy E. Grulke (1), Chris P. Andersen (2) and William E. Hogsett (2)
1. Pacific Southwest Research Station, USDA Forest Service, 4955 Canyon Crest Drive, Riverside, CA 92507, USA / 2. National Health and Environmental Effects Laboratory, US Environmental Protection Agency, 200 SW 35th Street, Corvallis, OR
97333, USA / Received November 24, 1999
Summary
Seasonal patterns of carbohydrate concentration in coarse and fine roots, stem or bole, and foliage of ponderosa pine (Pinus ponderosa Laws) were described across five tree-age classes from seedlings to mature trees at an atmospherically clean site. Relative
to all other tree-age classes, seedlings exhibited greater tissue carbohydrate concentration in stems and foliage, and greater
shifts in the time at which maximum and minimum carbohydrate concentration occurred. To determine the effect of environmental
stressors on tissue carbohydrate concentration, two tree-age classes (40-year-old and mature) were compared at three sites
along a well-established, long-term O3 and N deposition gradient in the San Bernardino Mountains, California. Maximum carbohydrate concentration of 1-year-old needles
declined with increasing pollution exposure in both tree-age classes. Maximum fine root monosaccharide concentration was depressed
for both 40-year-old and mature trees at the most polluted site. Maximum coarse and fine root starch concentrations were significantly
depressed at the most polluted site in mature trees. Maximum bole carbohydrate concentration of 40-year-old trees was greater
for the two most polluted sites relative to the cleanest site: the bole appeared to be a storage organ at sites where high
O3 and high N deposition decreased root biomass.
Keywords:
carbohydrate allocation, mature trees, multiple stressors, ozone exposure, Pinus ponderosa.
