reviewforexam2

Chapter 7: Forests: 

Chapter 7: Forests

Outlines: 

Outlines Introduction Forests as Multiple-Use Resources Forests as Fiber Resources Nonfiber Uses of Forest Resources Deforestation and Reforestation

Introduction: 

About 30% of the Earth’s land surface (excluding Antarctica) are covered with forest and woodland. Introduction

Introduction: 

This portion has changed considerably over the centuries, generally decreasing as cultivated land has expanded. The original forest cover of the Earth approached 50% of land area. Introduction

Forests as Fiber Resources: 

Forests as Fiber Resources Principles of Sustainable Forestry Forest Management Forest Products Technology

Principles of Sustainable Forestry: 

Principles of Sustainable Forestry Sustainable forest management means managing a forest in such a way that it will produce a given amount of timber each year indefinitely.

Slide7: 

The area of forestland that can be harvested each year on a sustainable yield basis is: Area of forestland available Number of years to maturity

Forest Harvest Techniques: 

Forest Harvest Techniques Clearcutting Selective Cutting Shelterwood Cutting Chipping

Slide9: 

Shelterwood cutting is a two-phase timber-harvesting technique in which not all trees are taken in the first phase so that some trees may provide shelter for young seedlings; when these are established, the remaining older trees are cut. Shelterwood cutting is an efficient technique in small plots with relatively homogenous tree species. It is costly in terms of labor inputs for larger acreages and so is not practiced widely on large tracts of commercial forestlands.

Slide10: 

Selective cutting is a timber-harvesting technique in which only trees of specified size or species are taken, leaving other trees. Selective cutting is used primarily in hardwood forests. When used in mixed-species forests, selective cutting leads to a loss of diversity. Selective cutting is costly and appropriate only when the value of the harvested trees is high relative to those left uncut.

Slide11: 

Clear-cutting is a forest harvest technique in which all trees in a particular area are cut, regardless of species or size. Clear-cutting is the most widely used method of harvesting and also the most controversial. About two-thirds of US timber production is harvested this way. Is appropriate when the tree are relatively uniform in species and age or when it provides the most desirable form of regeneration.

Slide12: 

It does remove the entire forest canopy and leads to soil erosion and wildlife habitat destruction. It also leaves a more disrupted and scarred landscape than other harvesting techniques. It produces much more timber per unit of acre harvested than selective cutting or shelterwood cutting.

Slide13: 

Biomass harvesting is a forest harvest technique in which whole trees are chipped and used as fuel or to make pulp. Chips are easier to handle in large quantities than logs and are easy for quick transportation. Loggers cut selectively or consume all standing timber, depending on the requirement of the job. The method has great economic appeal for harvesting the vast majority of US forestlands. It also is used in the developing world.

Silviculture: 

Silviculture Silviculture is intensive management of forest lands for increased production of trees. Intensive silviculture on productive lands produces much larger yields of timber than occur in natural forests. Intensive silviculture as a forest management strategy results from a shortage of timber available for harvest.

Use of Wood: 

Use of Wood In most of the world, harvested wood generally is used for fuel. In the industrialized world today, most wood is used for industrial purpose.

Nonfiber Uses of Forest Resources: 

Nonfiber Uses of Forest Resources Habitat Water Resources Recreation Carbon Storage The Role of Fire

Water Resources: 

Forest vegetation has two contrasting impacts on that runoff: it protects the quality of the water but decreases its quantity. In most cases, maintaining good water quality is a prime concern and thus takes precedence. Water Resources

Slide18: 

When a forest is harvested, the soils is disturbed, increasing the amount of overland flow and erosion, with negative impacts on water quality. In addition to regulating overland flow and erosion, forests play a critical role in evaportranspiration. When a large forest region is deforested, the decrease in evaportranspiration actually reduces the amount of water vapor in the air and thus may reduce precipitation.

Carbon Storage: 

Carbon Storage Much of the concern about tropical deforestation focused on its impacts on the global carbon cycle. We should not forget that fossil fuel combustion discharges vastly more carbon dioxide into the atmosphere than does deforestation.

The role of fire: 

The role of fire In the past, fire was believed to be harmful to forest, but today forest fires are recognized as a natural and important part of most forest ecosystems.

Slide21: 

Fires also have beneficial effects. They allow the release of nutrients stored in dead biomass, which stimulates growth after fire. They also remove old stands of timber that are particularly susceptible to insect or disease infestation, thus inhibiting the spread of pests. Removing the forest promotes rapid growth of early successional species. Most important, frequent fires allow accumulated fuel to burn off relatively harmlessly, preventing the severe fires that occur in areas of high-fuel buildup.

Slide22: 

There are three basic kinds of forest fires. Ground fires are fires that burn within the organic matter and litter of the soil. They smolder slowly and have little effect on trees. Surface fires burn on the ground surface, consuming litter as well as the herbaceous and shrubby vegetation of the forest floor. They burn faster than ground fires and clear all the low vegetation of the forest, but they have little effect on large trees.

Slide23: 

Crown fires burn treetops as well as low vegetation, usually killing all or almost all above-ground vegetation. These fires are the most destructive to timber, wildlife, and the soil.

Concerns about the Amazon Deforestation: 

Concerns about the Amazon Deforestation Loss of biodiversity: the tropical rainforests constitute only about 7% of the world’s area yet contain more than half of the world’s species. Emissions of carbon dioxide: first, they store large volumes of carbon in living biomass. Second, they have very high rates of productivity and thus have an enormous capacity to absorb carbon from the atmosphere.

Concerns about the Amazon Deforestation: 

Concerns about the Amazon Deforestation Disruption of regional hydrologic cycle: if the forests were removed, the amount of evapotranspiration would decrease. This would increase the runoff, causing more erosion, it would decrease atmospheric humidity and thus precipitation in the interior. Destruction of indigenous cultures: the Amazon is home to numerous groups of people, deforestation represent a significant disruption of established life-styles and a potential loss of the cultural knowledge of indigenous peoples.

The Siberian Forest: 

The Siberian Forest The Siberian forest is about 22% of the total forest area of the world and about 72% of the boreal or northern coniferous biome.

Slide27: 

Forest ownership is critical to forest management and timber supply.

Chapter 8: Biodiversity and Habitat: 

Chapter 8: Biodiversity and Habitat

Outlines: 

Outlines Introduction Value of Biodiversity Conservation of Biodiversity Conclusion

Introduction: 

Introduction Biological diversity refers to both the genetic variability among individuals of a species and the abundance of individuals within a species. The number of different species, the abundance of individuals in that species, and the number of species present at a particular time within a specific geographic area are also indicators of biological diversity. The most ecologically diverse environments are the tropical forests, where there is a much greater abundance of plant and animal species than in any other single biome.

Slide31: 

Loss of biodiversity has several consequences: Ecosystems are undermined. The possibility of using as yet untried species for food, fuel, fiber, or medicine disappears. Human appreciation and understanding of nature also are diminished.

Ecological Interaction: 

Ecological Interaction The stability of ecosystems, in terms of their ability to maintain populations of organism, is often enhanced by the diversity of organisms they contain. Diversity does not always lead to stability.

Potential Resources: 

Potential Resources Nature contains many things that we might use at some time in the future. Food and medicine are the most often-cited potential uses of wild plants and animals.

The Inherent Value of Species : 

The Inherent Value of Species Perhaps the most compelling reason for concerned about loss of biodiversity is the belief that we, as humans, have an obligation to respect the rights of other species to exist. Some neo-Darwinian view of extinctions cause by humans are no different from mass extinctions of the past such as the disappearance of the dinosaurs. This view maintains that species should be allowed to die because they have been unable to compete successfully with humans and other species.

Slide35: 

In the US, we make a distinction between endangered species and threatened species. Endangered species are defined as those in danger of becoming extinct throughout all or a significant part of their natual ranges. Threatened species are those species likely to become endangered in the near future.

Slide36: 

Even though a species may not be extinct, zoologists worry about the consequences of inbreeding among the relatively few members of a small population.

Slide37: 

Harvesting old-growth timber, such as this in the Hoh forest of Washington, threatens species such as the spotted owl and the marbled murrelet. Intense controversy continues in both the US and Canada over the ecological impacts of logging old-growth forests in the Pacific Northwest.

Causes of Biodiversity Loss: 

Causes of Biodiversity Loss Major Causes Habitat Modification Species Introductions Hunting Local or Regional Causes Pollution Diseases and parasites Consumption and trade Global warming

Conservation of Biodiversity: 

Conservation of Biodiversity Species Preservation Habitat Conservation The Endangered Species Act The Convention on Biological Diversity

Species Protection: 

Species Protection The most significant program aimed at restricting hunting and trade in endangered species is the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).

Habitat Conservation: 

Habitat Conservation The amount of land under some form of protection has grown dramatically in recent years and today accounts for about 6% of the world’s land area. A key part of this protection is the Biosphere Reserve Program of the United Nations Educational, Scientific, and Cultural Organization (UNESCO).

Slide42: 

To qualify as a biosphere reserve, and area must have outstanding, unusual, and complete ecosystems, with accompanying harmonious traditional human land uses. A reserve consists of a largely undisturbed core area surrounded by one or more buffer zones of human occupancy.

The Endangered Species Act: 

The Endangered Species Act The most comprehensive piece of legislation regulating protection of all species of flora and fauna is the Endangered Species Act (ESA), passed in 1973. The controversy started immediately after passage of the act, when a small fish was identified to be threatened by completion of the Tellico Dam in Tennessee.

Chapter 10: Water Quantity and Water Quality: 

Chapter 10: Water Quantity and Water Quality

Outlines: 

Outlines Water Supply and Its Variability Demand for Water Water Quality Water Pollution Control Quality, Quantity, and the Water-Supply Problem

Water Supply and Its Variability: 

Water Supply and Its Variability Water storages on the land are of two basic types: surface water and groundwater. Surface water is liquid water and floating ice above the ground surface, in rivers, swamps, lakes, or ponds. It is derived from direct precipitation or from subsurface sources. Groundwater is water below the ground surface, in a saturated zone below the water table.

Groundwater and Surface Water: 

Groundwater and Surface Water Figure 10.1: Groundwater occupies pore spaces below the surface. Surface water is found in lakes and streams.

Slide48: 

A porous body of material containing groundwater is called an aquifer.

Slide49: 

If the water table is free to rise with additional water, the aquifer is said to be unconfined; if there is an impermeable layer overlying the aquifer, it is described as confined. Such impermeable layers are called aquicludes, and they are particularly important in segregating relatively clean groundwater from brackish or contaminated groundwater.

Water Supply and Its Variability: 

Water Supply and Its Variability Spatial Variation in Surface Supply Temporal Variability Water Supplies and Storage

Spatial Variation in Surface Supply: 

Spatial Variation in Surface Supply The renewable supply of fresh water is directly determined by precipitation and evapotranspiration rates, with runoff being the difference between the two.

Temporal Variability: 

Temporal Variability Flows are more variable in small rivers and less variable in large rivers. In the tropics, seasonal variations in river flow usually correspond to seasonal patterns of rainfall. In midlatitude climates, low-flow periods usually occur in the summer because plants are using more water at this time.

Water Supply Systems: 

Water Supply Systems Figure 10.4: A typical water-supply system includes both natural and engineered components. Its overall capacity is limited by the component with the lowest capacity.

Slide54: 

Thus, although water supply is constrained by natural factors, water development in the form of engineering works also affects water availability. One indication of the extent of water use can be gained by comparing withdrawals to natural runoff.

Terms describe water use: 

Terms describe water use Withdrawal is the removal of water from a surface or groundwater source for a variety of purposes such as municipal, industrial, or irrigation use. Consumptive use is the use of that water in such a way that it is not returned to the stream or aquifer; instead, it is returned to the atmosphere by evapotranspiration. In-stream uses do not require removal of the water from a river or lake; these include navigation, wildlife habitat, waste disposal, and hydroelectric power generation.

Slide56: 

Depletion of stream flows caused by consumptive off-stream use, particularly irrigation, is a major problem in semiarid and arid portions of the United States.

Slide57: 

Most small-scale and domestic water-supply systems use groundwater, whereas large industrial and commercial users depend mainly on surface water. Typically, groundwater storages are replenished relatively slowly, taking years to centuries or more to replace the total volume of a given aquifer. As a result, it is possible to withdraw water much faster than it is replaced, a practice known as groundwater mining. In a few countries in the Middle East, total withdrawals of water exceed the renewable supply, indicating significant overdraft of groundwater at the national level.

Slide58: 

One impact of groundwater overdraft is declining well levels. A decline in the elevation of the freshwater table causes saltwater intrusion, an inland movement of the salt/fresh boundary, which contaminates wells and makes them unusable for drinking water.

Slide59: 

Groundwater overdrafts are causing subsidence, or sinking of the land; contributing to coastal flooding.

The Demand for Water: 

The Demand for Water Regional US demand is greatest in the western states, with water used for irrigating. The smallest withdrawals are in the Northeast, where most of this water is used for industrial purposes and steam electrical generation.

The Demand for Water: 

The Demand for Water Off-Stream Uses In-Stream Uses

Off-Stream Uses: 

Off-Stream Uses This include public supply, rural supply (domestic and livestock), industrial supply, irrigation, and hydroelectric power generation (an in-stream use). Public and rural supplies include both domestic and commercial uses of water, including those familiar to us in our everyday lives at home or at work—washing, cooking, drinking, lawn watering, sanitation, and the like.

Slide63: 

Agricultural uses, principally irrigation, consume more fresh water than any other use. Worldwide, agriculture uses about 71% of total freshwater withdrawals. This portion tends to be higher in developing than in industrialized countries. In the US, about 42% of water withdrawals are for irrigation. To conserve more of the water, irrigation system must become more efficient.

Slide64: 

Irrigation efficiency is defined as the volume of applied water in the root zone that is used by the crop. It is expressed as a percentage of the volume of water diverted from surface sources or pumped from groundwater supplies. Drip irrigation is one of the most efficient application methods, while flood, furrow, and sprinklers average between 60-80% efficiencies.

Slide65: 

Industry takes the second-largest share of the world’s water withdrawals, about 20%. Industrial uses include a wide range of activities, including water used for washing products in the manufacturing process, removing waste materials, and cooling. The greatest withdrawals of water in the industrial sector are for cooling thermal electric power plants. Industrial users are turning away from once-through systems toward water-recycling systems.

Slide66: 

Domestic uses take the least water, generally less than 10%, except in urbanized regions with relatively less industry and irrigation, such as South America and Oceania. Among the important domestic uses are cooking, laundry, bathing, toilet flushing, and , in North America, lawn irrigation. Domestic water use is not heavily consumptive—only about 8% in the US, and much of this is in irrigating lawns.

Waste Dilution: 

Waste Dilution The most important in-stream use of water is for waste dilution. Virtually all rivers in populated areas are used to remove wastes. The more water present and flowing in a river, the lower the concentration of pollutants will be, and thus the better water quality will be.

Hydroelectric Power: 

Hydroelectric Power Hydroelectric power is generated by storing water behind a dam and releasing it through turbines when electricity is needed. Because electricity cannot be stored in large quantities, timing of hydro-electric power production is relatively inflexible. In addition, the large dams best suited to generating electricity inundate large areas and alter river habitats, causing additional economic and ecological dislocations.

Water Quality: 

Water Quality Impurities in water come from many different sources, both natural and human, and it is often difficult to separate the two.

Slide70: 

Pollutants come from diverse human-made and natural sources. One way to classify pollutant discharges is by point versus nonpoint sources. A point source is a specific location such as a factory or municipal sewage outfall. A nonpoint source is a source that, as far as we know, originates from a large, poorly defined area. Runoff, subsurface flow, and atmospheric sources of water pollution are the primary nonpoint sources.

Water Quality: 

Water Quality Major Water Pollutants and Their Sources Groundwater Pollution Problems

Disease-Causing Organisms: 

Disease-Causing Organisms These are the bacteria, viruses, and parasites that cause disease in humans and livestock. Sewage pollution and livestock operations are their primary sources.

Plant Nutrients: 

Plant Nutrients Although aquatic plants need many different substances for growth, algal growth requires just a few key substances, primarily nitrogen and phosphorus.

Heat: 

Heat Electric power generation, petroleum refining, and many other industrial processes depend on the production and dissipation of large amounts of thermal energy—heat. Another cause of thermal pollution in streams is the removal of vegetation that shades the water, especially deforestation. The primary detrimental effects of thermal pollution are to fish.

Water Pollution Control: 

Water Pollution Control Wastewater Treatment Primary Secondary Tertiary Nonpoint Pollution Control Pollution Prevention

Wastewater Treatment: 

Wastewater Treatment Sewage treatment methods include primary, secondary, and tertiary techniques. Primary treatment consists of removal of solids by sedimentation, flocculation, screening, and similar methods. Primary treatment may remove about 35% of BOD, 10 to 20% of plant nutrients, and none of the dissolved solids.

Slide77: 

Secondary treatment removes organic matter and nutrients by biological decomposition, using methods such as aeration, trickling filters, and activated sludge. It moves about 90% of BOD, 30 to 50% of nutrients, and pherhaps 5% of dissolved solids. Tertiary methods have come into widespread use only in the past decade or so. There are many methods, and they vary considerably in their effectiveness, but generally they remove 50 to 90% of nutrients and dissolved solids.

Nonpoint Pollution Control: 

Nonpoint Pollution Control Nonpoint sources of pollution are the most difficult to control.

Slide79: 

The most cost-effective ways of reducing nonpoint water pollution is through watershed management.