Directed forest

A directed forest is a term for the unconnected directed graph in which every component of connection is a directed tree with a root. ... 

Lemma (2). For the graph Hha J u+ obtained by adding the arc u to the directed spanning tree HkA, the addition to the contour is the directed forest, apparently with one-node components whose roots are the nodes for the contour Ckail,. The lemma is evident. 

Stamm AJ (1959) Bound-water diffusion into wood in the fibre direction. Forest Products Journal, 9(1) 27-32... 

Of the total, US 1.4 billion were health costs (e.g., sore eyes, skin rashes), affecting around 70 million people in three countries (Schweithelm, 1999). Timber losses account for US 493 million. In agriculture (plantation and smallholdings), the cost is US 470.4 millions. Other costs are related to direct forest benefits, i.e., raw materials and food benefits, indirect forest benefits related to hydrology and soil conservation, and losses of international funding of biodiversity conservation. 

Also, for the complexes of combinatorial properties, the description can be more succinct when it uses the forbidden patterns instead of the allowed ones. For example, for the complex of disconnected graphs, the minimal non-simplices correspond to spanning trees. For the complex of directed forests, the minimal nonsimplices are all pairs of directed edges that have the same end vertex, together with all directed cycles. 

Makela, A., and Schopp, W. (1990). Regional-Scale SO Direct Forest Impact Calculations. In Alcamo, J., Shaw, R.W., and Hordijk, L. (eds.) The RAINS Model of Acidification Science and Strategies in Europe. Kluwer Publishers, Dordrecht (in press). 

The influence of human activities in a stream drainage basin can be relatively simple and direct, as in the disposal of soluble organic and inorganic waste, or more subtie and complex, as in the conversion of prairie or forest land to agricultural use. Such effects can be expected to increase as population density and agricultural, industrial, and mining activities increase. 

As with other factors, no direct statements can be made relating the reaction of a soil to its corrosive properties. Extremely acid soils (pH 4 0 and lower) can cause rapid corrosion of bare metals of most types. This degree of acidity is not common, being limited to certain-bog soils and soils made acid by large accumulations of acidic plant materials such as needles in a coniferous forest. Most soils range from pH5 0 to pH8 0, and corrosion rates are apt to depend on many other environmental factors rather than soil reaction per se. The 45-year study of underground corrosion conducted by the United States Bureau of Standards included study of the effect of soils of varying pH on different metals, and extensive data were reported. 

Sensitive ecosystems that cannot neutralize the unnatural levels of acidity are adversely affected. Soil nutrient systems may be altered with a resulting direct or indirect damage to forest. Aquatic habitats have been chemically altered and many lakes and streams no longer support the traditional life forms. Fish have been lost from many lakes with a resulting affect on other food-web elements. 

The burning of slash following deforestation, whether intentional or unintentional, results in far greater direct and indirect losses of nutrients than deforestation alone. This is particularly true in many tropical forests where only a small fraction (if any) of the aboveground biomass is removed prior to burning. Carbon losses from slash fires in the tropical dry forest were 4-5 fold greater than C losses from wood export (Table IV) (55). Slash fires in tropical dry forests resulted in N losses of 428-500 kg ha whereas fuel wood export of the relatively N-poor coarse woody debris amounted to approximately 41 kg N ha" Losses of P increase with increasing fire severity. P losses of 10-77 kg ha" as a result of severe fires is not uncommon (Table TV) (53, 58, 60). 

Cronan, C. S. (1984). Biogeochemical responses of forest canopies to acid precipitation. In "Direct and Indirect Effects of Acidic Deposition on Vegetation" (R. A. Linthurst, ed.), pp. 65-79. Butterworth, Boston, MA. 

The land biota reservoir (3) represents the phosphorus contained within all living terrestrial organisms. The dominant contributors are forest ecosystems with aquatic systems contributing only a minor amount. Phosphorus contained in dead and decaying organic materials is not included in this reservoir. It is important to note that although society most directly influences and interacts with the P in lakes and rivers, these reservoirs contain little P relative to soil and land biota and are not included in this representation of the global cycle. 

The low pH of acid precipitation can destroy forests and kill fish. Some lakes and streams lie in soil that has the natural ability to buffer the increased acidity of acid rain, usually because the soil contains a high amount of lime. Other lakes and streams, however, have no such buffering capacity. The pH of the water is not the main problem—at least not directly. The problem lies in the amount of aluminum compounds that are leached out of the soil surrounding the lake or stream at lower pHs. Aluminum is toxic to many aquatic species. 

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