Project at a Glance

Title: Effects of ozone and sulfur dioxide on forage and range species

Principal Investigator / Author(s): Youngher, V B

Contractor: University of California, Riverside

Contract Number: A0-055-31

Research Program Area: Ecosystem & Multimedia Effects

Topic Areas: Ecosystem Impacts


Red brome (Bromus rubens L) and tall fescue (Festuca arundinacea Schreb) plants were exposed to ozone and sulfur dioxide in a 2 x 2 factorial combination of treatments (0 and 0.20 ppm ozone; with 0 and 0.20 ppm sulfur dioxide) for 16 and 24 weeks, respectively. Five plants from each treatment (for each species) were harvested weekly or biweekly for tall fescue after eight weeks. The growth analysis variables mean relative growth rate, mean net assimilation rate, and mean leaf area ratio were calculated to attempt to identify stages of growth which were susceptible to pollutant stress, however, these variables did not prove to be sensitive indicators for the experimental objectives. Individual growth, weight, and quality variables were analyzed to evaluate altered carbon assimilation and/or partitioning patterns.

For red brome, ozone caused significant reductions in total dry weight (21.8%), top dry weight (21.7%), root dry weight (22.6%), and weight per tiller (44.4%). Number of tillers increased 48.2%. Total number of leaves increased (49.7%) primarily due to a great increase in accumulated dead leaves (109.3%) and to a lesser extent live leaves (21.9%). The total leaf area was significantly reduced (28.1%) and the specific leaf area reduced 41.2%. All these effects were significant at p < 50.01. Ozone also caused a slight increase in total number of inflorescences (8.6%), but decreases in numbers of flowering tillers (24%) and in total and individual weights of inflorescences (61.3 and 63.6%, respectively). Sulfur dioxide caused a 17.6% decrease in weight per inflorescence.

For quality parameters, ozone caused reductions in total ash (8.6%) and in the specific minerals calcium (11.5%), magnesium (16.2%) and phosphorus (14.5%). Sulfur dioxide did not affect total ash, but did reduce the individual minerals by 7.6% for calcium, 14.8% for magnesium and 11.5% for phosphorus. Crude fat content of herbage was reduced (7.8%) while crude protein was increased (6.7%).

Tall fescue plants were affected by sulfur dioxide with root weight being reduced 24% and total nonstructural carbohydrate content reduced 7.7%. Reasons for the reduced sensitivity of tall fescue to ozone and sulfur dioxide are discussed.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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