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Seasonal influences on ozone uptake and foliar injury to ponderosa and Jeffrey pines at a southern California siteAuthor(s): Patrick J. Temple; Paul R. Miller
Source: In: Bytnerowicz, Andrzej; Arbaugh, Michael J.; Schilling, Susan L., tech. coords. Proceedings of the international symposium on air pollution and climate change effects on forest ecosystems. Gen. Tech. Rep. PSW-GTR-166. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 221-228
Publication Series: General Technical Report (GTR)
Station: Pacific Southwest Research Station
PDF: View PDF (660 KB)
DescriptionAmbient ozone was monitored from 1992 to 1994 near a forested site dominated by mature Jeffrey and ponderosa pines (Pinus jeffrey Grev. & Balf. and Pinus ponderosa Dougl. ex Laws.) at 2,000 m in the San Bernardino Mountains of southern California. Ozone injury symptoms, including percent chlorotic mottle and foliage retention, were evaluated on 130 mature pines in September of 1991 to 1994 at a site 2 km from the ozone monitor. Symptom measurements were combined in an ozone injury index (OII) that represented the average crown condition of each plot. Leaf stomatal conductance and available soil water were measured biweekly from March to November at one of the plots from 1992 to 1994. Mean annual ozone concentrations were relatively constant for the 3 years. However, the distribution of individual trees in the 0 to 100 range of the OII showed a shift from 1991 to 1994 to higher frequencies of trees in classes representing greater amounts of injury. Compared with 1991, in 1993 and 1994 more trees remained in the higher injury classes. Maximum rates of stomatal conductance and maximum ozone uptake occurred in June of each year, but the total annual ozone flux varied as the amount of available soil water varied with seasonal precipitation. The period of April to June or May to July, depending upon year, accounted for 70 to 75 percent of annual ozone flux, confirming the high correlation observed between ambient ozone concentrations from April to June and development of chlorotic mottle on the needles. Foliar injury to current-year needles, which served as a marker of ozone response for a single exposure season, was greatest in 1992, coincident with higher flux of ozone to foliage in 1992, compared with 1993 and 1994. These data confirm that the period of maximum ozone impact on these pines is early in the growing season, and that ambient ozone after July had less effect on the development of foliar ozone injury on older pine needles. Year-to-year variation in ozone injury to pines was influenced both by the status of soil moisture availability in summer at this location and the internal foliar dynamics of the trees as they recovered from drought.
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CitationTemple, Patrick J.; Miller, Paul R. 1998. Seasonal influences on ozone uptake and foliar injury to ponderosa and Jeffrey pines at a southern California site. In: Bytnerowicz, Andrzej; Arbaugh, Michael J.; Schilling, Susan L., tech. coords. Proceedings of the international symposium on air pollution and climate change effects on forest ecosystems. Gen. Tech. Rep. PSW-GTR-166. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 221-228
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