Pigment-based identification of ozone-damaged pine needles as a basis for spectral segregation of needle conditions.
ABSTRACT Air pollution affects large areas of forest, and field assessment of these effects is a costly, site-specific process. This paper establishes a biochemical basis for identifying ozone-damaged pine trees to facilitate efficient remote sensing assessment of air pollution damage. Several thousand live needles were collected from ponderosa pine (Pinus ponderosa) and Jeffrey pine (P. jeffreyi) trees at three sites in Plumas National Forest and Sequoia-Kings Canyon National Park. These needles were assembled into 504 samples (based on the abaxial surface) and grouped according to five dominant needle conditions (green, winter fleck, sucking insect damage, scale insect damage, and ozone damage) and a random mixture of needles. Pigment concentrations per unit needle area of chlorophyll a, chlorophyll b, and total carotenoids were measured. The following pigment concentration ratios were calculated for all samples: chlorophyll a/total carotenoids, chlorophyll b/total carotenoids, total chlorophyll/carotenoids, chlorophyll a/chlorophyll b. The group of ozone-damaged needles had significantly lower mean pigment concentrations (family-wise p < 0.01) and significantly lower mean chlorophyll a/total carotenoid and total chlorophyll/total carotenoid ratios (family-wise p < 0.01) than all other groups of needles. Ozone-damaged needles had a significantly lower mean chlorophyll a/chlorophyll b ratio than all other groups except one (family-wise p < 0.01). Linear discriminant analysis with three factors (chlorophyll a concentration, the chlorophyll a/carotenoid ratio, and the chlorophyll a/chlorophyll b ratio) and subsequent maximum likelihood classification of damaged and non-damaged needles gave an overall cross-validated accuracy of 96%. These ozone-damaged needles are biochemically unique in relation to other needle conditions in this study, and further research is needed to generalize these results.
- Plant Disease - PLANT DIS. 01/1983; 67(10).
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ABSTRACT: We investigated the time-course of Rubisco small subunit (Rubisco-SSU) oxidation in leaves of bean plants grown under elevated O3. Five ambiences were tested in open-top chambers (OTCs): non-filtered air (NF), NF+20, +40, +60 and +80 ppb O3. An unchambered atmosphere was also available. Four samplings were performed between 8 and 30 days after emergence. The dynamics of oxidation was studied with reference to leaf type (primary or trifoliate), leaf age and exposure duration. The oxidation was measured using an ELISA quantification of carbonyls present on amino acid side chains of Rubisco-SSU. Ozone was able to induce carbonyl derivative formation in both primary and trifoliate leaves. This oxidation process was always accompanied with visible foliar damage. As regards primary leaves, the oxidation varied with ozone dose and leaf age. A convenient ozone dose expressed as accumulated exposure over a threshold of 40 ppb (AOT40) is able to induce oxidation in mature leaves but not in very young leaves. Once near-full leaf span was reached, the carbonyl content had a good correlation with the ozone dose. In trifoliate leaves, ozone-induced oxidation of Rubisco-SSU was consistently lower and much less organized. Twenty-two days after emergence, a synthetic cumulative oxidation index computed per plant was linearly increased when plotted against AOT40. Finally, the time course of oxidation was discussed with special reference to the development pattern of leaf.Plant Science - PLANT SCI. 01/2003; 165(3):613-620.
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ABSTRACT: The greatest air pollution impacts in forests of California are the physiological disturbances imposed on trees as a result of the combined effects of excess N and phytotoxic ozone exposure (Takemoto et al., 2001). In highly-polluted stands in the San Bernardino Mountains in southern California, fine root biomass is greatly reduced and C cycling within the tree and within the ecosystem is also significantly altered. Air pollution effects appear to be more subtle over most of the Sierra Nevada. Individual trees with significant amounts of ozone injury in the southern and western edge of the Sierra have been identified in previous surveys. Additional significant environmental impacts of N deposition in southern California forest and chaparral ecosystems include high NO3− concentrations in streamwater and groundwater and increased greenhouse gas emissions from soil. Nitrogen deposition in the Sierra Nevada does not appear to be sufficiently high to cause major physiological impacts or widespread deterioration of water quality, although it is possible that chronic N deposition may be at least partially offsetting the depressive growth effects of ozone in the southern Sierra. However, unusually high nitrate concentrations frequently occur in a chaparral catchment with high N deposition inputs in Sequoia National Park. Preliminary results from N deposition measurements, streamwater analyses for NO3−, and soil and plant indicators of N enrichment suggest that N cycling in the mixed conifer forests in the Mountain Home State Park region in the southwestern Sierra Nevada is being altered by N deposition to a greater extent than similar forests in Sequoia National Park. Ozone and N deposition levels are relatively low in high-elevation ecosystems of the Sierra Nevada and do not appear to have severe impacts, although N deposition in the southern Sierra may contribute to the natural peak in nitrate in runoff during early snowmelt. In forests throughout California, periodic droughts and stand densification from long-term fire suppression are major risk factors responsible for reduced tree vigor, greater mortality and predisposition to disease and insect attack; the latter a common ultimate cause of tree mortality. Current land management plans for the Sierra Nevada focus on decreasing overstocking of stands and reducing fuel loads and wildfire risk.Developments in Environmental Sciences.