Effects on Forests

Under low-dose conditions, forest ecosystems act as sinks for atmospheric pollutants and in some instances as sources. As indicated in Chapter 7, the atmosphere, lithosphere, and oceans are involved in cycling carbon, nitrogen, oxygen, sulfur, and other elements through each subsystem with different time scales. Under low-dose conditions, forest and other biomass systems have been utilizing chemical compounds present in the atmosphere and releasing others to the atmosphere for thousands of years. Industrialization has increased the concentrations of NO2, SO2, and CO2 in the clean background atmosphere, and certain types of interactions with forest systems can be defined. 

Forests can act as sources of some of the trace gases in the atmosphere, such as hydrocarbons, hydrogen sulfide, NO, and NH3. Forests have been identified as emitters of terpene hydrocarbons. In 1960, Went (10) estimated that hydrocarbon releases to the atmosphere were on the order of 108 tons per year. Later work by Rasmussen (11) suggested that the release of terpenes from forest systems is 2 x 10 tons of reactive materials per year on a global basis. This is several times the anthropogenic input. Yet, it is important to remember that forest emissions are much more widely dispersed and less concentrated than anthropogenic emissions. Table 8-2 shows terpene emissions from different types of forest systems in the United States. 

Forest systems also act as sources of CO2 when controlled or uncontrolled burning and decay of litter occur. In addition, release of ethylene occurs during the flowering of various species. One additional form of emission to the atmosphere is the release of pollen grains. Pollen is essential to the reproductive cycle of most forest systems but becomes a human health hazard for individuals susceptible to hay fever. The contribution of sulfur from forests in the form of dimethyl sulfide is considered to be about 10-25% of the total amount released by soils and vegetation (12). 

Trees and soils of forests act as sources of NH3 and oxides of nitrogen. Ammonia is formed in the soil by several types of bacteria and fungi. The volatilization of ammonia and its subsequent release to the atmosphere are dependent on temperature and the pH of the soil. Fertilizers are used as a tool in forest management. The volatilization of applied fertilizers may become a source of ammonia to the atmosphere, especially from the use of urea. 

Nitrogen oxides are formed at various stages of the biological denitrification process. This process starts with nitrate as the nitrate is reduced through various steps, NO2, NO, N2O, and N2 can be formed and, depending on the conditions, released to the atmosphere. 

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The second level of interaction, the intermediate-dose level, can result in measurable effects on forest ecosystems. These effects consist of a reduction in forest growth, change in forest species, and susceptibility to forest pests. Both laboratory investigations and field studies show SO2 to be an inhibitor of forest growth. When various saplings have been exposed to SO2 in the laboratory, they show reduction in growth compared with unexposed... 

Wert, S. L. A system for using remote sensing techniques to detect and evaluate air pollution effects on forest stands, pp. 1169-1178. In Proceedings of the Sixth International Symposium on Remote nsing of the Environment. Vol. 2. Ann Arbor University of Michigan, 1%9. 

Michalzik, B., T. Mueller, and B. Stadler. 1999. Aphids on Norway spruce and their effects on forest floor solution chemistry. Forest Ecology and Management 118 1-10. 

Woodbury, P. B., Heath, L. S., and Smith, J. E. (2006). Land use change effects on forest carbon cycling throughout the Southern United States. J. Environ. Qual. 35,1348-1363. 

OZONE AIR POLLUTION IN THE SIERRA NEVADA - DISTRIBUTION AND EFFECTS ON FORESTS, II... 

Permethrin. Terrestrial impact studies on single and double applications of 17.5 g permethrin/ha to forest ecosystems have revealed little or no adverse effects on forest songbirds, small mammals, honeybee colonies, or ground insects, but short-lived and sometimes heavy knockdown of arboreal and flying invertebrates have been documented (42-44). Extensive aquatic impact studies... 

McLeod, B.B. Millikin, R.L. "Environmental impact assessment of experimental spruce budworm adulticide trials Effects on forest avifauna" Report FPM-X-54, Forest Pest Management Institute Sault Ste. Marie, Ont., 1982. 

An appreciable amount of NH3 volatilizes from soil. In some fields, up to 50% of the added ammonium-N volatilizes. In addition to the economic importance of this nitrogen loss, there is also environmental importance. In industrialized regions of the world, NH3 in the atmosphere approaches concentrations high enough to cause toxicity effects on forests. 

Overrein L., Seip H.M. and Tollan A., Acid precipitation - effects on forest and fish. Final report. 175 pp. Oslo-As (1980). 

Well, I could only offer you to fix all the figures here at this round table. We could include some proposals for the outcome of the meeting or we could sit together and make some detailed proposals. I think the discussion is not the place of very detailed figures to solve this problem. However, lUFRO-values ought to be respected, because lUFRO represents all forest research organizations of the world which work on the problem of air pollution and its effects on forests. 

Sverdrup, H Warft inge, R, and Nihlgard, B. (1994). Assessment of soil acidification effects on forest growth in Sweden. Water Air Soil Pollut.. 78, 1-36. 

Scandinavian and European studies, including the Norwegian Interdisciplinary Research Programme Acid Precipitation—Effects on Forest and Fish, and the study by the European Organization for Economic Cooperation and Development, elucidated the effects of acid rain on fish and forests and long-distance transport of pollutants in Europe. 

Tynnyrinen, S., Palomaki, V., Holopainen, T., Kiirenlampi, L., 1992. Comparison of several bioindicator methods in monitoring the effects on forest of a fertilizer plant and a strip mine. Ann. Bot. Fenn. 29, 11-24. 

The Hubbard Brook Experimental Forest is a long-term ecological research site established by the U.S. Department of Agriculture Forest Service in the White Mountains of New Hampshire to investigate the structure and function of forest and aquatic ecosystems, and their response to disturbance (Likens and Bormann 1995 Groffman et al. 2004). Hubbard Brook was the site where acidic deposition was first reported in North America (Likens et al. 1972). Hubbard Brook receives elevated inputs of acidic deposition and the forest ecosystem is very sensitive to these inputs. There have been long-term measurements and studies of acidic deposition and its effects on forests and streams at Hubbard Brook (Likens et al. 1996 Driscoll et al. 2001). 

Pennanen, ., Perkiomaki, J., Kiikkila, 0.,Vanhala, P., Neuvonen, S. and Fritze, H. (1998) Prolonged, simulated acid rain and heavy metal deposition separated and combined effects on forest soil microbial community structure. FFMS Microbial Ecology 2 7, 291 -300. 

A special research project Acid precipitation - Effects on Forest and Fish" (the SNSF-project) was established in Norway in 1972 with participation from a number of research institutions. Work under this project will continue until 198O and form the basis for a future monitoring programme. 

L. Overrein et al Acid Precipitation - Effects on Forest and Fish Final Report of the SNSF Project 1972-1980 SNSF - Project FR 19/80 Norwegian Inst. Water Research 1980. 

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