This study aimed to explore if changes in peak ozone (O3) concentrations may reinforce the phytotoxic effects of air concentration of acidifying compounds and their deposition, as well as unfavorable climatic factors on pine crown defoliation. Forty-eight pine stands with more than 8000 sample pine trees have been monitored annually. The impact of sulfur dioxide (SO2) on pine defoliation was found to be the most significant. The impacts of peak O3 concentrations, acid deposition, and amount of precipitation were considerably lower, whereas the impact of air temperature, the least. Contribution of peak O3 concentrations to the integrated impact of acid deposition and amount of precipitation on pine defoliation was most significant, whereas the contribution to the impact of acidifying air compounds, mainly SO2, was the least. No synergetic effect between peak O3 concentrations and high temperature during vegetation period was detected.

Algirdas Augustaitis

Ingrida Augustaitiene

Almantas Kliucius

Rasele Girgzdiene

Dalia Sopauskiene

Contribution of Ambient Ozone to Changes in Scots Pine Defoliation. Step II of Lithuanian Studies

Atmospheric bulk deposition of heavy metals (HM) was measured from 1972/73 to the present time at five to ten forest sites in rural areas of Denmark. From 1979, HM in aerosols were measured at one to four forest sites. On the basis of these long-term continuous measurements, the atmospheric inputs to the forest floor have been calculated. Yearly HM emission estimates to the European atmosphere seems to correlate well with yearly average values of HM deposition, as well as with HM concentrations in the ambient atmosphere. HM emissions have been estimated since the 1950s. Using the correlation between emission and deposition, HM deposition values maybe extrapolated in reverse chronological order. The accumulated atmospheric HM deposition has been estimated in this way over a period of 50 years.

M. F. Hovmand

Kaare Kemp

Atmospheric Heavy Metal Input to Forest Soils in Rural Areas of Denmark

Plant strategies to survive ozone stress include exclusion or tolerance of ozone.  If these processes fail, past observations of ozone injury have indicated many physiological and metabolic changes then occur; most of these changes are likely to have been initiated at the level of gene expression, suggesting signal transduction.  In the last decade considerable understanding of the biochemical process within plants has been developed.  Currently there are several hypotheses regarding a response of plants to ozone fumigation: [1] membrane dysfunction and alteration of purpose; [2] stress ethylene interactions; [3] impairment of photosynthesis via changes in Rubisco levels and the guard cells so that the stomata do not track correctly the environment; [4] antioxidant protection through metabolites and enzyme systems to reduce the oxidant load; and [5] general impairment or disruption of metabolic pathways.Many believe that free radicals and other oxidative products, formed in plant leaves under ozone exposure, are responsible for much of the spread of the biochemical alterations.  There are obvious chemicals that may account for the changes that are observed, such as hydrogen peroxide.  Once the ozone enters the tissue, evidence suggests the first line of defense is a range of antioxidants, such as ascorbate, glutathione peroxidase, superoxide dismutase, and catalase. If overwhelmed, subsequent events occur which are highly suggestive of systemic acquired resistance.  Furthermore, other defensive indicators, such as salicylic acid and jasmonic acid, tend to increase, but more slowly than ethylene, and spread their signaling effects more widely in the plant.The primary set of metabolic reactions that ozone triggers is thought to be “wounding“ responses with a secondary response of senescence.  The dramatic strides in understanding the genetic make-up of plants, gene control, and signal transduction/control over the last few years will only accelerate in the future.  We need now to have an understanding of those events that can be translated into more detailed schemes of how ozone alters much of the basic metabolism of plants and how plants counteract or cope with ozone.  What is now known about how varied biochemicals and their pathways are changed upon ozone exposure will be discussed.

Robert L. Heath

Alterations of the Biochemical Pathways of Plants by the Air Pollutant Ozone: Which are the True Gauges of Injury?

Ozone (O3) is supposed to represent a significant risk for the health of forest ecosystems in Central Europe. So far, however, its impact on stands growing under natural conditions has not been clearly proved. A new project of the National Agency for the Research in Agriculture is focused on the O3 effect on selected parameters of forest health. This paper presents the results of the first year of monitoring, 2005. In 2005, high O3 concentrations were measured, mainly in the spring. In the summer, due to wet and cold weather, the O3 load was comparatively low. In the plots investigated, the concentrations of O3 were higher with the altitude. The amount of epicuticular waxes on 1-year-old Norway spruce needles was the only factor showing significant correlation to O3 concentration. Defoliation of the stands depended only on the stand age. The amount of malondialdehyde (MDA), an oxidative stress marker, was related to the altitude, and only for European beech. The results are preliminary, as the summer O3 development was not typical in 2005, and the results may change over the next monitoring periods.

Vít Šrámek

Radek Novotný

Emilie Bednárová

Hana Uhlírová

Monitoring of Ozone Risk for Forests in the Czech Republic: Preliminary Results

Maintaining healthy forests is the major objective for the Forest Service scientists and managers working for the U.S. Department of Agriculture. Air pollution, specifically ozone (O3) and nitrogenous (N) air pollutants, may severely affect the health of forest ecosystems in the western U.S. Thus, the monitoring of air pollution concentration and deposition levels, as well as studies focused on understanding effects mechanisms, are essential for evaluation of risks associated with their presence. Such information is essential for development of proper management strategies for maintaining clean air, clean water, and healthy ecosystems on land managed by the Forest Service. We report on two years of research in the central Sierra Nevada of California, a semi-arid forest at elevations of 1100–2700 m. Information on O3 and N air pollutants is obtained from a network of 18 passive samplers. We relate the atmospheric N concentration to N concentrations in streams, shallow soil water, and bulk deposition collectors within the Kings River Experimental Watershed. This watershed also contains an intensive site that is part of a recent Forest Service effort to calculate critical loads for N, sulfur, and acidity to forest ecosystems. The passive sampler design allows for extensive spatial measurements while the watershed experiment provides intensive spatial data for future analysis of ecosystem processes.

Carolyn Hunsaker

Andrzej Bytnerowicz

Jessica Auman

Ricardo Cisneros

Air Pollution and Watershed Research in the Central Sierra Nevada of California: Nitrogen and Ozone

The forests of the San Bernardino Mountains have been subject to ozone and nitrogen (N) deposition for some 60 years. Much work has been done to assess the impacts of these pollutants on trees, but little is known about how the diverse understory flora has fared. Understory vegetation has declined in diversity in response to elevated N in the eastern U.S. and Europe. Six sites along an ozone and N deposition gradient that had been part of a long-term study on response of plants to air pollution beginning in 1973 were resampled in 2003. Historic ozone data and leaf injury scores confirmed the gradient. Present-day ozone levels were almost half of these, and recent atmospheric N pollution concentrations confirmed the continued air pollution gradient. Both total and extractable soil N were higher in sites on the western end of the gradient closer to the urban source of pollution, pH was lower, and soil carbon (C) and litter were higher. The gradient also had decreasing precipitation and increasing elevation from west to east. However, the dominant tree species were the same across the gradient.Tree basal area increased during the 30-year interval in five of the sites. The two westernmost sites had 30–45% cover divided equally between native and exotic understory herbaceous species, while the other sites had only 3–13% cover dominated by native species. The high production is likely related to higher precipitation at the western sites as well as elevated N. The species richness was in the range of 24 to 30 in four of the sites, but one site of intermediate N deposition had 42 species, while the easternmost, least polluted site had 57 species. These were primarily native species, as no site had more than one to three exotic species. In three of six sites, 20–40% of species were lost between 1973 and 2003, including the two westernmost sites. Two sites with intermediate pollution had little change in total species number over 30 years, and the easternmost site had more species in 2003. The easternmost site is also the driest and has the most sunlight filtering to the forest floor, possibly accounting for the higher species richness. The confounding effects of the precipitation gradient and possibly local disturbances do not show a simple correlation of air pollution with patterns of native and invasive species cover and richness. Nevertheless, the decline of native species and dominance by exotic species in the two westernmost polluted sites is cause for concern that air pollution is affecting the understory vegetation adversely.

Edith B. Allen

Patrick J. Temple

Michael J. Arbaugh

Abby G. Sirulnik

Leela E. Rao

Patterns of Understory Diversity in Mixed Coniferous Forests of Southern California Impacted by Air Pollution

The presented study aimed to explore the relationships between ambient ozone (O3) and tree defoliation, specific diversity, and abundance of soil microarthropods, stream macroinvertebrates, and small mammals (mainly rodents) in order to test the hypothesis that changes in the considered objects of the forest ecosystem could be related to changes in ambient O3, concentration of which is below critical level. The observations were carried out from 1994 at three integrated monitoring stations. The obtained data revealed that only peak O3 concentrations (from 125–215 μg·m-3) had significant effect on changes in the considered components of forest biota.

Gintautas Mozgeris

Gintaras Pivoras

Kestutis Arbaciauskas

Irena Eitminaviciute

Reda Mazeikyte

Trend in Ambient Ozone and an Attempt to Detect Its Effect on Biota in Forest Ecosystem. Step I of Lithuanian Studies

Unfavorable anthropogenic factors, such as air pollution, lead to biochemical responses in trees. Changes in the amounts of secondary metabolites may be early indicators of invisible injuries. The aim of this study was to evaluate composition of the essential oils in the needles of Scots pine (Pinus sylvestris L.) growing in the areas affected by pollutant emissions of main factories in Lithuania: a nitrogen fertilizer factory (NFF), a cement factory (CF), and an oil refinery (OR). Totally, 14 pine stands were examined along transects from the factories (July 2005). Volatile components of the needles were extracted and analyzed by GC and GC/MS. Over 70 components of the essential oils were identified in current-year and 1-year-old needles.Along the CF transect for current-year needles, the percentage of diterpenes was decreasing with the increasing pH of the pine bark (r = -0.582; p &lt; 0.05) or with the increasing concentration of SO2 (r = -0.573; p &lt; 0.05); for 1-year-old needles, the percentage of diterpenes was decreasing with the increasing pH of the bark (r = -0.534; p &lt; 0.05). Along the OR transect, in both the current-year and 1-year-old needles, the percentage of diterpenes was decreasing with the increasing SO2 (respectively, r = -0.773; p &lt; 0.01; r = -0.486; p &lt; 0.05); an opposite relation was true for sesquiterpenes (respectively, r = -0.751; p &lt; 0.01; r = 0.785; p &lt; 0.01). The view was different along the NFF transect. For current-year needles, the percentage of monoterpenes was decreasing with the increasing NH3 (r = -0.669; p &lt; 0.01); while the percentage of sesquiterpenes or oxysesquiterpenes was increasing with the increasing NH3 (respectively, r = 0.540; p &lt; 0.05 and r = 0.688; p &lt; 0.01). For each transect, cluster analysis of the percentages of components of essential oils in the needles allowed us to distinguish the most contrasting stands according to the concentration of air pollutants. Current-year needles were more effective as indicators of the effects of pollution than 1-year-old needles in the case of the NFF and the OR transects, and both-aged needles were equally valuable in the case of the CF transect. The changes detected in the proportions of components of the essential oils in the needles of the trees affected by the industrial emissions may play a significant role in modifying the susceptibility of the pine stands to the biotic factors, and also may alter emissions of terpenes from the stands to the atmosphere.

Asta Judzentiene

Aida Stikliene

Eugenija Kupcinskiene

Changes in the Essential Oil Composition in the Needles of Scots Pine (Pinus sylvestris L.) Under Anthropogenic Stress

The chemical composition of throughfall depends on the age of the Norway spruce (Picea abies Karst) stands and season of the year. The pH of throughfall decreased and the amount of hydrogen ion in throughfall deposited to the soil increased with increasing age of spruce stands, especially in the winter season. Concentrations of K+, H+, SO42−, Mn2+, and NH4+ in throughfall were higher than bulk precipitation for the whole year and K+, H+, and Mn2+ concentrations were higher in throughfall in winter and the growing season. This indicates that these ions were washed out or washed from the surface of needles and/or the bark, and that NO3−, NH4+, Ca2+, Mg2+, Fe2+, and Zn2+ were absorbed in the canopy. The effect of high nitrogen deposition, above critical loads, and an increase in the amount of sulfur and in the sum of the strong acids (S-SO42− and N-NO3−) that reached the soil with throughfall may have implications for the vitality of spruce stands, especially in older age classes. The application of Principal Component Analysis (PCA) has led to identification of five factors responsible for the data structure (“mineral dust”, “acidic emissions”, “heavy metals-dust particles”, “ammonium [NH4+]”, and “H+”). They explain more than 60% of the total variance system. The strong positive correlation between stand age class and ionic concentrations in throughfall occurs for all year and the winter period for ions within the following categories: “acidic emissions”, SO42− + NO3−; “heavy metals-dust particles”, Fe2+ + Mn2+ + Zn2+; “mineral dust”, Na+ + K+ + Ca+2 + Mg2+; “NH4+”; and “H+”. The strength of the relationship decreases in the growing period, probably due to processes occurring in the canopy (adsorption, leaching, etc.).

Stanislaw Malek

Aleksander Astel

The Effect of Stand Age on Throughfall Chemistry in Spruce Stands in the Potok Dupniański Catchment in the Silesian Beskid Mountains, Southern Poland

The forests of North America provide a variety of benefits including water, recreation, wildlife habitat, timber, and other forest products. However, they continue to face many biotic and abiotic stressors including fires, native and invasive pests, fragmentation, and air pollution. Forest health specialists have been monitoring the health of forests for many years. This paper highlights some of the most damaging forest stressors affecting North American forests in recent years and provides some projections of future risks.

Borys Tkacz

Ben Moody

Jaime Villa Castillo

Forest Health Status in North America

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