Grantee Research Project Results
Final Report: Impact of Ambient O3 on Physiological, Visual, and Growth Responses of Sensitive Eastern Hardwood Tree Species Under Natural and Varying Site Conditions
EPA Grant Number: R825244Title: Impact of Ambient O3 on Physiological, Visual, and Growth Responses of Sensitive Eastern Hardwood Tree Species Under Natural and Varying Site Conditions
Investigators: Skelly, John , Steiner, Kim C. , Davis, Donald D.
Institution: Pennsylvania State University
EPA Project Officer: Chung, Serena
Project Period: November 1, 1996 through October 31, 1999 (Extended to October 31, 2001)
Project Amount: $494,000
RFA: Air Quality (1996) RFA Text | Recipients Lists
Research Category: Air , Air Quality and Air Toxics
Objective:
The objectives of this project were to:- Determine O3 exposure/response relationships in the ontogeny of visible foliar injury symptoms on O3 sensitive forest tree species under ambient O3 exposures and under natural forest conditions within forests of central Pennsylvania.
- Determine, under open-top and natural forest conditions, the interrelationships between micro-site factors and leaf physiological responses leading to differences in foliar symptom expressions of two O3 sensitive and one O3 tolerant species within forests of central Pennsylvania.
- Determine pre-visual changes in cellular Rubisco as an indicator of threshold cumulative ambient O3 exposures and to detect relationships to subsequent physiological manifestations, symptoms, premature senescence, and growth patterns of two O3 sensitive and one O3 tolerant species within forests of central Pennsylvania.
- Determine whether radial growth or the relationship between ring-width variation and climate differ in relation to foliar O3 symptom severity within and among natural populations of three O3-sensitive hardwood tree species (black cherry, white ash, and yellow poplar) in the Shenandoah National Park and black cherry within the forests of central Pennsylvania.
Summary/Accomplishments (Outputs/Outcomes):
Studies were conducted within a former nursery bed area at Penn Nursery, Bureau of Forestry, Centre County, PA. One year-old seedlings of Prunus serotina Ehrh. (BC), Fraxinus americana L. (WA), and Acer rubrum L. (RM) were planted in August 1997 within six open plots (Amb), six open-top chambers each receiving either carbon-filtered (FF; 50% Amb) air or non-filtered (NF, 98% Amb) air. Within each plot, 36 (16 x BC, 10 x WA, 10 x RM) seedlings were planted. For BC, one ozone sensitive (R-12) and three ozone tolerant open-pollinated families (M-7, M-2, and R-14) were planted. Two water regimes were imposed with nine randomly assigned plots being irrigated every 2-5 days depending upon natural weather conditions and nine having no artificial watering throughout the 1999 growing season. Gas exchange, ozone-induced foliar injury, and growth were intensively measured during the seasons of 1998 and 1999. Ambient ozone concentrations were continuously monitored throughout both growing seasons. Meteorological data and soil water potential were recorded during the 1998 and 1999 growing seasons. The weather conditions for the early growing season of 1999 were hotter and substantially drier than for the same time in 1998. Ambient ozone concentrations and their durations were sufficient during both years to induce typical visible foliar ozone injury on black cherry (0-34 percent total affected leaf area) and red maple (<1 percent total affected leaf area) seedlings. Soil moisture conditions for the dry and wet plots were similar for most portions of the 1998 season, but differed significantly in 1999. During both seasons, there was a positive correlation between the increasing cumulative ozone uptake and the increasing percent of total affected leaf area by foliar stipple for BC seedlings.At the end of both seasons, there were no significant differences in symptom expression among the BC genotypes. In 1998, seedlings seemed to be in the stage of establishment and the differences in gas exchange between the ozone and soil moisture treatments were inconsistent and insignificant. In 1999, significant variation for gas exchange was found across species, soil moisture conditions, ozone exposures, time of day, leaf position, and sample date (P<0.001). Seedlings grown under wet soil moisture conditions performed significantly higher gas exchange than seedlings grown under dry soil moisture conditions among similar ozone exposures for all three species. Gas exchange was highest for the upper crown leaves and in the afternoon for BC, WA, and RM. Black cherry and WA performed similar ozone uptake but only BC developed ozone-induced adaxial stipple. There was a significant site effect (P<0.001) only for the lower crown leaves when comparing ambient ozone uptake and decreased photosynthetic activity. The more severely injured BC seedlings grown under wet soil moisture conditions tended to have an increased growth production in height. It appears that controlled wet soil moisture conditions favor ozone uptake and increasing foliar injury followed by decreasing photosynthetic activity, but relationships between stomatal behavior and symptom development are species specific.
The second portion of the investigation was conducted within a natural forested site located within the Rothrock State Forest surrounding the Penn Nursery of Pennsylvania's Bureau of Forestry, Centre County, PA. The crowns of five BC, five WA, and six RM canopy trees grown on two apparently different natural dry and wet sites were made accessible by scaffold towers for intensive physiological measurements. A natural creek within the wet site had running water throughout the entire summer seasons of 1998 and 1999. Gas exchange and leaf water potential were measured during the growing seasons of 1998 and 1999. Visible foliar injury was assessed on the same three upper and three lower crown branches throughout both seasons. Ambient ozone concentrations and meteorological data were continuously monitored at a distance of approximately 500 m from the center of the forest site. The weather conditions for the early growing season of 1999 were hotter and substantially drier than for the same time in 1998. Ambient ozone concentrations and the duration were sufficient during both years to induce typical visible foliar ozone injury on black cherry canopy trees (0-5 percent total affected leaf area). During both seasons, there was a positive correlation between the increasing cumulative ozone uptake and the increasing percent of total affected leaf area by foliar stipple for BC canopy trees. The lower crown leaves and the BC trees grown under dry soil moisture conditions tended to show more severe foliar injury than the upper crown leaves and when compared to the BC trees grown under wet soil moisture conditions. There were no significant differences detected in leaf water potential. During both seasons, significant variation for stomatal conductance was found across species, soil moisture conditions, time of day, and sample date (P<0.01). Black cherry and RM grown under dry soil moisture conditions performed higher gas exchange than BC and RM canopy trees grown under wet soil moisture conditions. White ash canopy trees responded with a significant increase of gas exchange after accessing higher crown branches via increasing the height of the scaffold by 1.5 m. These observations suggest a stronger influence of available photosynthetic radiation on leaf gas exchange as compared to the influence of naturally differing soil moisture conditions for this species. Although BC and WA performed similar ozone uptake only BC developed ozone-induced adaxial stipple. Only for RM canopy trees was there a significant site effect (P<0.001) when comparing ambient ozone uptake and decreased photosynthetic activity. The strong differences in gas exchange response within the same crowns of WA canopy trees and the uncoupling relationship between stomatal conductance and photosynthetic activity demonstrate the strong influence of the heterogeneous environmental conditions as they typically occur within the canopy. The later development of visible foliar injury for BC canopy trees compared to BC seedlings with similar stomatal conductance suggests a more efficient defense or repair system within the leaves of mature trees.
The data collected on the Rubisco portion of this extensive investigation is under analysis and interpretation at the time of the report submission. One and possibly two journal articles are anticipated which will present the results of the 3 years of sample collections and leaf protein analyses from: (1) seedlings within the open-top chamber investigations grown under differing ozone exposures, and (2) mature canopy trees growing under natural forest conditions and ambient ozone exposures. We regret the delay in presenting these results but excellent data and continuing interpretations assure eventually successful publication.
The general objective of the fourth portion of these investigations was to determine whether radial growth, or the relationship between tree ring-widths and climate, varies in relation to leaf O3-sensitive hardwood species: black cherry (Prunus serotina Ehrh.), white ash (Fraxinus americana L.), and yellow-poplar (Liriodendron tulipifera L.). Mature forest trees to be used in this study were previously described, permanently identified, and evaluated for foliar O3 injury by Hildebrand. They occupy three distinct locations, representing different elevations and other site characteristics, within the Shenandoah National Park.
For each species, data analyses were planned to address the following hypotheses: (1) there is no difference in tree-ring response to climate variation among groups representing different leaf O3 injury classes, (2) there is no difference among leaf O3 injury classes in basal area growth, and (3) there is no difference among leaf O3 injury classes in response to exogenous stand disturbance. However, with the exception of one tree core collection, the sample trees yielded chronologies that are too short to perform the types of time series analyses needed to address hypotheses 1 and 3. Thus, only hypothesis 2 could be evaluated.
In general, the growth regressions illustrate the expected overriding importance of factors directly or indirectly relating to photosynthetic capacity, such as sapwood area, tree size and crown dimensions, on basal area growth. These factors were included in the independent variable set in an attempt to avoid confounding varying tree size, as it may relate to growing space and local site conditions, with leaf O3 injury. Partial confounding of O3 injury with location is one possible explanation for only a secondary component of Leaf O3 injury appearing in the regressions for black cherry and white ash. Such confounding may arise from apparently differing ambient O3 regimes among the three sites which, in turn, produce varying leaf injury symptom severities. The presence of this albeit weak indication of a growth relationship with O3 sensitivity for black cherry and white ash, but not yellow-poplar, generally follows published species differences in foliar O3 sensitivity. Controlled fumigation studies with seedlings generally rank black cherry as highly sensitive, followed by white ash and then yellow-poplar, with the latter two often indistinguishable. Hildebrand's data for the trees in this study similarly showed a general pattern of decreasing foliar O3 injury scores from black cherry to white ash and yellow-poplar, with yellow-poplar injury scores being markedly lower than the others.
Growth Comparisons with O3 Sensitivity. Comparisons of relative growth (RBAI) of trees in each O3 injury class were evaluated by species for combined locations. Black cherry trees were grouped into five relative leaf injury classes described as none, trace, slight, moderate, and severe. Patterns of RBAI, the mean growth of trees within O3 sensitivity classes relative to the asymptomatic group, show a general tendency for reduced growth among the higher sensitivity classes. However, the ANOVA F-test was not significant, nor Dunnett's test of means for the control (asymptomatic) group compared to the other sensitivity classes. Similar non-significant results were obtained for white ash and yellow-poplar, each of which were divided into four O3 sensitivity classes. Only the severe O3 sensitivity class showed any indication of reduced growth for white ash, while there was no suggestion of a growth relationship with increasing O3 sensitivity for yellow-poplar. The power of the analyses was reduced by small numbers of trees in the higher O3 sensitivity classes for all species but yellow-poplar.
Conclusions:
The multiple regression and ANOVA results were generally complimentary in suggesting a possible weak relationship of reduced radial growth of black cherry and white ash, but not yellow-poplar trees, with increasing O3 sensitivity. These tentative findings also agree with published rankings of O3 sensitivity based on leaf injury for these three species. Although the results lack a clear statistical basis for other than a conjectural conclusion, our findings encourage further pursuit of the question of O3-induced growth impacts on mature, forest-grown black cherry and white ash in the Shenandoah National Park and other localities where comparatively high ambient O3 concentrations occur. Major limitations to a more robust analysis in this study are a lack of more sample trees within the higher leaf O3 injury categories and short tree-ring chronologies, which constrained the types of statistical procedures that could be used to assess other hypotheses originally presented.Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 15 publications | 5 publications in selected types | All 2 journal articles |
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Type | Citation | ||
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Schaub M, Skelly JM, Steiner KC, Davis DD, Pennypacker SP, Zhang J, Ferdinand JA, Savage JE, Stevenson RE. Physiological and foliar injury responses of Prunus serotina, Fraxinus americana, and Acer rubrum seedlings to varying soil moisture and ozone. Environmental Pollution 2003;124(2):307-320. |
R825244 (Final) |
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Zhang JW, Schaub M, Ferdinand JA, Skelly JM, Steiner KC, Savage JE. Leaf age affects the responses of foliar injury and gas exchange to tropospheric ozone in Prunus serotina seedlings. Environmental Pollution 2010;158(8):2627-2634. |
R825244 (Final) |
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Supplemental Keywords:
ambient air, air, atmosphere, ozone, ecological effects, dose-response, oxidants, scaling, terrestrial, environmental assets, biology, pathology, ecology, monitoring, northeast, EPA Region 3, Pennsylvania, PA, agriculture, forestry., RFA, Scientific Discipline, Air, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Ecology, Ecosystem/Assessment/Indicators, Ecosystem Protection, exploratory research environmental biology, Chemical Mixtures - Environmental Exposure & Risk, State, Ecological Effects - Environmental Exposure & Risk, Ecological Effects - Human Health, Ecology and Ecosystems, tropospheric ozone, Atmospheric Sciences, Ecological Risk Assessment, Biology, Ecological Indicators, ecological exposure, ecological effects, environmental monitoring, growth response, ambient ozone data, Virginia (VA), Pennsylvania, growth rate, ambient air, forest ecosystem, climate variations, leaf physiological responses, air pollution models, National Ambient Air Quality Standards, atmospheric chemical cycles, chemical kinetics, ecological assessment, ozone induced foliar damage, ozone sensitivity, atmospheric reaction products, sensitive tree species, ecological response, Eastern hardwood tree, PA, ambient aerosol particlesRelevant Websites:
http://www.eintoday.com
http://www.research.psu.edu./erri
http://www.psu.edu/dept/airpollforeff/
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.