The United States is not considered water-scarce, but some parts of the country are.
Water use in the United States is out of control, so water scarcity is definitely in our future if we continue to use water at our current, furious rate.
The water that we use for all of our activities comes from the hydrologic cycle.
Water used in our home, manufacturing, cooling equipment that generate electricity, and irrigating croplands are a few examples.
The chart below shows trends in water withdrawals and population from 1950-2010.
The nation's water use peaked in 1980 and has been fairly constant since.
Since 1980, there have been many stresses for greater water use, such as population, irrigation of crops to feed this larger population, and more industry, yet total water use has not risen.
The fact that water use has leveled off despite the increase in these stresses is a good sign.
Emergency water relief plans and rules about lawn watering are some of the environmental news stories we hear.
Water is a difficult business.
Many people think that water should be free, which makes it hard for politicians to put restrictions on water use.
We can take a bucket from the lake and no one will arrest us for stealing.
You should be aware of the concepts of human water rights for the AP Environmental Science Exam.
The idea of a riparian right is the first.
Riparian means of, on or relating to the banks of a natural course of flowing water and is the right of people who have legal rights to use that area.
Water rights are given to people who have historically used the water in a certain area.
It is proposed that we simply take tons of ocean water and desalinate it, but it is not currently economically viable on a large scale.
As water becomes scarcer globally, it will be important for countries to think of ways to regulate the use of water.
As global water crises become more common, research into the economic viability of desalination has increased.
After answering the questions in the drills found on the next few pages, move on to the next chapter.
The soil is an important player in Earth's interdependent systems.
An essential link between the abiotic and the biotic is the soil, which plays a crucial role in the lives of plants, animals, and other organisms.
The pedosphere is the interface of the other four systems or spheres: the atmosphere, hydroosphere, and biosphere.
In the next chapter, we'll see how soil plays a role in the cycling of nutrients.
You will be expected to know the major characteristics of the soil for the test.
We may be tempted to think of soil as just a dirt, but it's actually a complex, ancient material teeming with living organisms.
45% of the soil is mineral in the form of rocks broken down into tiny particles.
The air and water fill the pores between the soil particles.
About 5% is organic matter.
In just one gram of soil, there may be as many as 50,000 organisms.
There are a number of physical and chemical features in the soil.
The USDA divides soil particles into three sizes.
The class with the smallest particles is clay.
Sand is the coarsest soil, with particles of 0.05-2.0mm in diameter.
Sand particles are usually too spherical in shape and too large to stick together; sand particles have more room for water but less ability to hold it.
Clay particles are easier to adhere to because they are small and flat and there is less room for water.
The soil is very small with a high proportion of clay particles.
The texture of a soil is determined by the proportion of these three classes.
The texture of a soil is determined by which particle size is most dominant.
A soil's texture is called loam if it has less than half of the three size classes considered optimal for plant growth.
The soil's acidity or alkalinity is an important characteristic.
The concentration of hydronium (H 3 O + ) in the solution is a measure of the substance's pH.
In the laboratory, the soil's water component's pH is measured by suspending the soil in water or a neutral salt solution.
Most soils range in pH from being neutral to slightly acidic.
It's important that the soil's pH is right because it affects the ability of plants to absorb certain vitamins and minerals.
If the soil in the region is acidic or basic, the plants won't be able to use certain soil nutrients.
The College Board wants you to know that when the soil solution becomes more acidic, it will be easier to remove heavy metals from the soil.
These ion can travel to streams and rivers and harm plants and animals.
The gills of fish can be damaged by aluminum ion.
The combination of organic material and rock that has been broken down by chemical and biological weathering is called soil.
The identity of the base rock of the region will affect the types of minerals found in the soil.
Water, wind, temperature, and living organisms are all prominent agents of weathering, and all weathering processes are placed into the following three broad categories.
Any process that breaks rock down into smaller pieces without changing the chemistry of the rock is called physical weathering.
The forces that cause physical weathering are wind and water.
Chemical weathering occurs as a result of chemical reactions of rock with water, air, or dissolved minerals.
Minerals are broken down or restructured in chemical processes.
In warm or moist environments, this type of weathering tends to dominate.
When iron and other metallic elements come in contact with water, they form rust.
Weathering that takes place as a result of the activities of living organisms can be done through physical or chemical means.
It is a physical process when tree roots enlarge the cracks in rocks.
Plants growing on rocks release organic acids that destroy minerals.
Different layers make up the soil.
Understand the different types of weathering processes and the order of the soil layers.
Each of the layers of the soil has its own physical, chemical, and biological properties.
The diagram illustrates and describes the different horizons.
Not every soil has all of them.
The layer is made up of organic matter.
The decomposing bodies of organisms and animal waste are included.
humus is a dark material that is left after most organic matter has been destroyed.
A horizon is the topmost mineral horizon and the most weathered soil layer.
The dark color is due to organic matter in the O horizon.
In soils that do not have an E horizon, this may be called the zone of leaching.
The horizon is called the eluviated horizon.
It is light in color and coarse in texture, and no organic matter has traveled down from the A horizon.
The E horizon can be found in soils that have been developed under forest.
The subsoil is where organic matter, clay, and minerals washed out of the upper horizons accumulate.
The zone of illuviation is called the zone of accumulation.
The parent material is loose enough to be dug up with a shovel.
The soil has identifiable features of the parent material because of the minimal weather at this depth.
The horizon has less activity than the one above it.
Beneath the soil lies a layer of unweathered rock.
This isn't part of the soil because it hasn't been weathered.
The R horizon has the same source minerals as the parent material, if the material from which horizons A through C was not transported from elsewhere.
Regolith is a word meaning "blanket or surface rock" in ancient Greek.
Waterborne minerals, humus, and other materials are moved from higher soil layers to lower soil layers.
The downward movement of water is due to gravity.
These materials are deposited in a lower soil horizon.
eluviation refers to the loss of dissolved organic and chemical compounds from the soil by draining into the ground.
The answer is A.
There are four basic processes that work on soil minerals and particles, organic matter, and soil chemistry.
There are four processes that include additions of materials from off-site, losses through erosion or leaching or biological activity, vertical translocations or movement from one soil horizon to another, and transformations of materials in place by weathering or chemical activity.
Six soil-forming factors influence the processes of soil development.
It takes a long time for a soil to develop its characteristic layers.
Any soil you see is a dynamic formation produced by the effects of climate and biological activity, as modified by topography and human influences, acting on parent materials over time.
The acronym Cl-O-R-P-T-H stands for six soil-forming factors.
There is a summary of how each factor works.
Climate involves differences in temperature and precipitation across the globe, and both heat and water facilitate chemical and biochemical reactions.
The weather affects processes such as freeze-thaw cycles.
Climate plays a role in determining what organisms grow in a location.
Different local conditions support different organisms, which influence the soil in a variety of ways.
Microorganisms transform minerals into different forms by decomposing organic matter.
Animals move soils, consume vegetation, and add nitrogen through waste and decomposing bodies.
Plants perform physical weathering through root growth, taking up soil and water, and altering soil chemistry in a number of ways.
Relief affects erosion in two ways--which locations are likely to lose surface material through the action of wind and rain, and which locations are likely to accumulate eroded material.
Different locations receive different amounts of sun.
Relief influences what organisms grow in a location.
The starting point for soil development is the parent material.
Its mineral properties affect how it is weathered.
The soil that develops at each location is dependent on parent material.
Slopes and depressions where material is lost and gained can take a long time to develop.
The effects of human activity must be acknowledged as a factor in soil development.
Acid rain and pollution change the chemistry of the soil.
Construction activities like digging and plowing tend to haploidize soils by mixing them.
The traffic of vehicles and machinery, erosion, and salinization are caused by human activities.
We need enough arable land to meet our agricultural needs in order to be able to grow all of the food we consume.
Nitrogen, K, and P are essential to plants and are provided by soil fertility.
The types of soils that are considered the best for plant growth are composed of a balanced mixture of clay, silt, and sand.
The structure of the soil is an important characteristic for agricultural purposes.
The soil is formed and held together by substances such as clay particles and organic matter.
Good structure can be found in the most fertile soils.
Arable soil takes a long time to form and is considered a non-renewable resource.
It takes 500 to 1,000 years to form a single inch of soil, and at least 3000 years to form enough fertile soil to support crop growth.
The texture and structure of the soil can be changed by certain agricultural activities, for example, repeated plowing can break down soil aggregates, leaving "plow pan" or "hard pan," which is unfertile soil.
In modern agriculture, the monoculture or the planting of just one type of crop over a large area is what dominates.
In the history of agriculture, there has been a decrease in the number of crop species and in the genetic makeup of individual species.
There are a lot of problems created by this.
Crops are more susceptible to pests and diseases because of a lack of genetic variation.
The consistent planting of one crop in an area eventually causes the soil in that area of the specific nutrients that the plant needs to grow.
Crop rotation, in which different crops are planted in the area in each growing season, is one way to prevent this phenomenon.
Polyculture is a practice that farmers will use to increase their sustainable practices.
This increases the number of animals.
The reliance on large machinery and the fact that agriculture is a huge consumer of energy are some of the problems with modern agriculture.
Fossil fuels are used to run farm machinery, as well as in the production of pesticides and fertilizers.
The mechanization of farming that resulted from the Industrial Revolution has resulted in a huge increase in worldwide agricultural productivity over the past 50 years.
The Green Revolution, a boom in agricultural productivity, has had detrimental effects on the environment.
The emergence of a new variety of pesticide-resistant insects was a result of the use of chemical pesticides.
The introduction of genetically modified plants has made it possible for researchers to solve the problem of pesticide-resistant insect species.
The increase in irrigation worldwide was one of the drawbacks of the Green Revolution.
Salt forms a layer on the surface of the soil when it dries out.
This leads to land degradation.
In order to combat this problem, researchers have developed drip irrigation, which only gives an area as much water as is necessary and delivers it directly to the roots.
The small rock fragments that result from weathering may be moved to new locations in the process of erosion, and bare soil is more susceptible to erosion than soil covered by organic materials.
The constant movement of water and wind on Earth's surface causes the erosion of soil.
It can become a problem for humans when soil is deposited in undesirable places.
Farmers who need healthy soil for planting and people who rely on bodies of water to be uncontaminated with soil runoff are at risk of being in bodies of water.
Slash-and-burn agriculture, which is characterized by cutting down and burning trees to clear land for agricultural purposes, is the most significant portion of erosion caused by humans.
The removal of plants makes the soil more vulnerable to erosion.
Human activities have increased the levels of erosion in the upper layers of soil.
Farmers searching for arable land will continue to face problems until new techniques that preserve the integrity of the soil are introduced.
Several best management practices have been developed to conserve soil resources.
These practices return organic matter to the soil, slow down the effects of wind, and reduce the damage to the soil from plowing.
Some of the more common methods are listed here.
The amount of organic matter in the soil can be increased by using animal waste, compost, and plants.
The practice of organic agriculture uses compost, manure, crop rotation, and non-chemical methods to enhance soil fertility and control pests.
Genetically modified organisms and pesticides are not used by organic producers.
Modification of practices to reduce the amount of erosion.
No-till farming, contour plowing, and strip planting are included.
Trees and other wind barriers can be used to reduce erosion.
Much of what we know about soil is new.
The creation of the Soil Conservation Service was made possible by the Soil Conservation Act of 1935.
The Dust Bowl of the 1930s was a period of unprecedented dust storms caused by severe drought and ill-advised farming practices.
The agency was founded by Hugh Bennett.
It was to promote sustainable soil practices among farmers and other land owners and to help restore ecological balance across the nation's landscape.
The agency has a new name.
The federal government was aware of the need to protect the nonrenewable resource.
There are two laws related to preserving soil.
This list can be used to review the key terms.
When you are writing an essay, keep these terms in mind.
The online companion for this book is Student Tools, where you can find all the Key Terms lists.
You can download a PDF of Chapter 4 Drill.
Four suggested answers or completions are followed by each of the questions or incomplete statements.
Pick the one that is the best.
Chapter 13 has answers and explanations.
Water vapor and carbon dioxide absorb the heat from the Earth and warm the atmosphere.
Imagine a place with cold waters, low oxygen levels, and fish.
Scientists designed an experiment to learn more about the functioning of the forest's cycle.
They used two areas of the same size and geologic features to cut all the trees from one plot.
They were able to measure the amount of water that flowed out of the two plots and the amount of phosphorus found in the water.
The two areas received the same amount of precipitation.
Both plots had the same amount of soil phosphorus.
Give an explanation as to why there is little organic matter in the rain forest soil.