Research Program Area: Ecosystem & Multimedia Effects
In order to determine the effects of chronic exposure to ozone and sulfur dioxide on yield and forage quality, seven forage and seven range grasses were exposed to various levels of the pollutants in closed fumigation chambers. Ozone levels were 100, 67, 33, and 0 percent of ambient. Sulfur dioxide was supplied at 10 pphm. The interaction of pollutants and defoliation was also investigated. Yield parameters studied were total forage dry weight, tiller production and dry weight per tiller. The quality parameters were forage content of nonstructural carbohydrates, crude protein, crude fiber, calcium, magnesium and phosphorus.
Chronic ozone exposure affected yield in varying degrees in all of the forage grasses. Effects were also observed on all quality parameters but species differed in their responses. The most pronounced response was in soluble carbohydrate levels. In general, cool-season grasses showed greater effects from ozone than warm-season species. Sulfur dioxide effects were more limited. Pollutant interaction was noted only in one case. At the end of the treatment period, interactions between pollutant exposure and simulated grazing (defoliation) were found for yield and some mineral components in several species.
Similar but less pronounced effects were noted for the range species, however, significant pollutant interaction was noted in two species. Pollutant-defoliation interaction was also observed in two species. Ambient ozone levels were markedly lower during this study period than they were during the forage study. Because species differed in their growth responses to the pollutants, possible changes in species composition of natural grasslands subjected to air pollution must be considered.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
Stay involved, sign up with CARB's Research Email Distribution List