Forest systems

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). 

The third category for interactions is high dose (III). The effects produced by this level of interaction can be seen by the casual observer. The result of high-dose exposure is destruction or severe injury of the forest system. High-dose conditions are almost always associated with point source emissions. The pollutants most often involved are SO2 and hydrogen fluoride. Historically, the most harmful sources of pollution for surrounding forest ecosystems have been smelters and aluminum reduction plants. 

The impact of acid deposition on forests depends on the quantity of acidic components received by the forest system, the species present, and the soil composition. Numerous studies have shown that widespread areas in the eastern portion of North America and parts of Europe are being... 

When a forest system is subjected to acid deposition, the foliar canopy can initially provide some neutralizing capacity. If the quantity of acid components is too high, this limited neutralizing capacity is overcome. As the acid components reach the forest floor, the soil composition determines their impact. The soil composition may have sufficient buffering capacity to neutralize the acid components. However, alteration of soil pH can result in mobilization or leaching of important minerals in the soil. In some instances, trace metals such as Ca or Mg may be removed from the soil, altering the A1 tolerance for trees. 

There has been very little research conducted on the morama bean, largely because it is found in the wild and only consumed by a small percentage of the population in the coimtries where found. However, in these areas, it is used by indigenous communities as a source of food, feed, shelter, and medicine, thus contributing to improve the quality of life in traditional agricultural and forest systems in various ways. The morama has enormous potential value that needs to be exploited for the... 

Brinkman, W. L. F. 1983. Studies on hydrobiogeochemistry of a tropical lowland forest system. Geojournal 11 89—101. 

With the efforts of conservation-minded citizens like President Theodore Roosevelt and Gifford Pinchot, America s first native-born professional forester, the United States Government soon became involved in preserving land and forming national parks. In fact, Roosevelt was so impressed with Muir and the need to protect our environment that he created five national parks overall. He added 140 million A (57 million ha) to the national forest system and set aside 18 areas of historic or natural interest (Bade, 1924). Yellowstone became the first national park in 1872, and with Muir s help was followed by the establishment of the Yosemite, Grand Canyon, Sequoia, and Mount Rainier national parks. In 1892, Muir established an organization that is now called the Sierra Club. 

Management of bark beetles in the forest system requires a knowledge of the elements which potentially regulate them. 

It is the intent of this paper to explore the various control tactics that are being suggested in the management of bark beetles in the forest system with specific attention given to the potential impact on the predator population. Similar arguments could be extended to other bark beetle mortality agents such as the parasite community. Primary examples and control tactics discussed will be drawn from our experience with the southern pine beetle, I). frontalis, a major pest in the southeastern U.S., along with other bark beetles in North America. 

The autotrophic microphytes in the soil and aquatic forest systems, and the aquatic macrophytes in the ponds, rivers and streams provide the habitat and food resource for many phytophagous organisms. 

Wang, E.X. and Benoit, G. (1996) Mechanisms controlling the mobility of lead in the spodosols of a Northern hardwood forest system. Environ. Sri. TechnoL, 30, 2211-2219. 

A sensitive and convenient forest parameter must be found to monitor the extent and intensity of stress on expansive forest systems. 

What is needed at this point are quantitative data on phenolic acid utilizing microbes (e.g., bacteria, fungi, actinomycetes) in field soils + phenolic acid enrichment during the spring, summer, and fall for various crop and forest systems. In addition, we need quantitative data describing the relationships between bulk-soil and rhizosphere phenolic acid utilizing microbes and the observed phytotoxicity of phenolic acids for sensitive species, i.e., a form of dimension analysis utilizing equations to predict useful and/or consistent relationships. 

This chapter reviews the distribution, mechanism and impact of mineral tunnelling by soil ectomycorrhizal fungi (EMF). Most trees in boreal forests live in close relation with EMF (Smith Read, 1997). These EMF mediate nutrient uptake they form an extension of the tree roots. In turn they obtain carbohydrates from the tree. Over the years ectomycorrhizal (EM) research has a strong focus on nutrient acquisition by EMF from organic sources (Read, 1991). In boreal forest systems, however, minerals could also be an important nutrient source, especially for calcium, potassium and phosphorus (Likens et al, 1994, 1998 Blum et al, 2002). Recent developments in EM research suppose a role for EMF in mobilizing nutrients from minerals (see Wallander, Chapter 14, this volume). 

Nortcliff, S., J. B. Thornes, and M. J. Waylen. 1979. Tropical forest systems a hydrological approach. Amazoniana 4 557-568. 

Heterotrophic nitrification has been studied in terrestrial systems, especially acid forest soils, where it has been difficult to document autotrophic nitrification. Experiments using isotopes to differentiate production of N03 from inorganic and organic substrates in a forest system found that heterotrophic nitrification accounted for less than 10% of the total nitrification rate (Barraclough and Puri, 1995). No information of this sort is available on the occurrence or significance of heterotrophic nitrification in aquatic systems. The potential for NH3 and N02 oxidation by heterotrophic bacteria in aquatic systems warrants further exploration, and the capability may be present in many strains already in culture. If heterotrophic nitrification is common in nature, then a focus on autotrophic nitrification as the... 

Witkamp M. and Ausmus B. S. (1976) Processes in decomposition and nutrient transfer in forest systems. In The Role of Terrestrial and Aquatic Organisms in Decomposition Processes (eds. J. M. Anderson and A. Macfadyen). Blackwell, Edinburg, pp. 75-396. 

The question of loss of metals from galaxies is profound because of the existence of metals in low column density Lyman-a forest systems (Ellison et al. 1999), which are probably gas clouds residing outside of galaxies. Where the heavy elements came from in these systems is still a mystery it is possible that they were seeded with elements... 

Corresponding to the analogy with potassium, a radiocesium cycle has been established in forest ecosystems which prevents radiocesium being lost from the mineral cycles of forest systems (Riesen, 2002). Either no or only very little radiocesium is lost by diffusion into the deeper zones of the soils (Sheppard and Thibault, 1991). [Under the presumption that the pH-value of the soils is low (<5.5) and there is a lack of potassium in the soils, these two conditions are fulfilled for almost all forests in Europe.] Almost all radiocesium cycles in the forest ecosystem function in the same... 

Fig. 15.4. Simulated plant production (a), soil carbon (0-50 cm depth) and soil respiration (b), and nitrogen and phosphorus soil mineralization (c) for Hawaii humid tropical forest systems during 4.1 million years of soil development. Observed data are plotted on the graphs, and observed net primary production is assumed to be equal to 0.7 times annual soil respiration.

Ecosystem effects soils, freshwater, and forest systems... 

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