What is the Great Green Wall?
A wall in China consisting of 300 million trees beginning in 1950s
* shelter-forest to defend China against dust storms from the Gobi Desert.
Cause of China's deserts
Climate formed them, but human activity enlarged it.
Removal of forests, over collection of firewood, overgrazing.
* 8% of China's land area is desert
Soil
The uppermost layer of Earth's crust, which supports terrestrial plants, animals, and microorganisms
-consists of mineral and organic matter modified by the natural actions of weather
How is soil formed?
Interaction among parent material (rock slowly broken down), climate, organisms, time, and topography. Biological, chemical, and physical weathering processes slowly break parent material into smaller and smaller particles.
How are organisms and climate involved in the formation of soil?
Plant roots and other organisms respire, producing carbon dioxide which diffuses into the soil and reacts with soil water to form carbonic acid. Other organisms produce other acids. These acids help break down rocks.
Climate- weathering is sped up by weat
Topography
a region's surface features
What are the 4 components of soil?
1. Inorganic nutrient minerals: 45%- from weathered parent material, provides anchorage and essential nutrient minerals for plants, pore space for water and air
2. Organic materials: 5%- decompose releasing essential nutrient mineral ions in to the soil
3
What is humus?
Partially decomposed organic material, primarily from plant and animal remains.
Soil rich in this has a loose, somewhat spongy structure with several properties, such as increased water-holding capacity, that are beneficial for plants and other organisms
illuviation
The decomposition of leached material in the lower layers of soil.
Soil horizons
the horizontal layers into which many soils are organized, from the surface to the underlying parent material
Name the horizons from top to bottom
O-horizon
A-horizon
E-horizon
B-horizon
C-horizon
S-olid parent material (bed rock)
Otto Ate Every Banana & Crapped Solid parent material...
soil profile
a vertical section from surface to parent material, showing the horizons
O-Horizon
uppermost layer of soil
rich in organic material
plant litter decays here
Desert- typically no O
A-Horizon
topsoil
dark & rich (Mmmmm) in accumulated organic matter and humus
nutrient poor because of deeper layer leaching
E-Horizon
in some soils, a heavily leached horizon like this develops between the A and B
B-Horizon
lighter-colored subsoil beneath the A-horizon, often a zone of accumulation in which nutrient minerals that leached out of the topsoil and litter accumulate
*typically rich in iron and aluminum compounds and CLAY.
C-Horizon
contains weathered pieces of rock and borders the unweathered solid parent material
- below the extent of most roots and is often saturated with groundwater
ecosystem services
Important environmental benefits, such as clean air to breathe, clean water to drink, and fertile soil in which to grow crops, that ecosystems provide
Nutrient cycling
the pathway of various nutrient minerals or elements from the environment through organisms and back to the environment
-nutrient minerals removed from soil by plants are returned when plants or the animals that eat the plants die and are decomposed by so
What do worms do?
Earthworms ingest soil and obtain energy and raw materials by digesting some of the compounds that make up humus.
Castings (bits of soil passed through the gut) are deposited on the soil surface.
They bring deeper minerals to the upper layers.
Earthworm t
mycorrhizae
symbiotic relationships between fungi and the roots of vascular plants
mycelium
The part of the fungus responsible for extracellular digestion and absorption of the digested food
loam
Rich, fertile soil that is made up of clay, sand, and silt.
IDEAL AGRICULTURAL SOIL
soil taxonomy
classification of soils
Spodosols
colder climates, ample precipitation, usually forms under coniferous forest and has an O-horizon of acidic litter, leached E-horizon, dark brown B-horizon
does not make good farmland, too acidic, nutrient poor
Alfisols
rich in accumulated humus, light colored E, B is rich in clay, C with weathered parent material, when soil is cleared for farmland, fertilizers must be used to maintain fertility
Mollisols
temperate, semi-arid grasslands, fertile soil, this A rich in humus, this B rick in calcium carbonate,
Aridisols
found in arid regions of all continents, lots of leaching, lack of vegetation, salty A, some provide rangeland for grazing animals, crops only if water is supplied by irrigation
Oxisols
highly weathered A, thick B highly leached, acidic, nutrient poor, low in nutrient minerals, tropical & subtropical regions,
sustainable soil use
the wise use of soul resources, without a reduction in the amount of fertility of soil, so that it is productive for future generations
soil erosion
the wearing away or removal of soil from the land
What % of US cropland is eroded?
Soil erosion declined to about 38% between 1982 and 1997
Where is soil erosion greatest?
certain parts of Asia, Africa, and Central and South America.
* in India and China an estimated annual 6.6 and 5.5 billion metric tons respectively is lost to erosion
The American Dust Bowl
more than 30 million hectares of the land in the Great Plains were damaged during the Dust Bowl years.
states who suffered the most: Colorado, Kansas, Oklahoma, Texas, and New Mexico
Causes of the Dust Bowl
-throughout late 19c and 20c, much of the native grasses were removed to plant wheat
-between 1930-1937 the semiarid lands from Oklahoma to Canada received 65% less rainfall
-drought caused crop failure
-winds from West caused dust storms
Only 16% of the world's farmland...
does not have soil fertility problems such as poor drainage, aluminum toxicity, acidity, salinity, low soil nutrients, depletion of organic matter
salinization
the gradual accumulation of salt in a soil, often as a result of improper irrigation methods
desertification
degradation of once-fertile rangeland, agricultural land, or tropical dry forest into nonproductive desert
conservation tillage
a method of cultivation in which residues from previous crops are left in the soil, partially covering it and helping to hold it in place until the newly planted seeds are established
crop rotation
the planting of a series of different crops in the same field over a period of years
contour plowing
plowing that matches the natural contour of the land
strop cropping
a special type of contour plowing
produces alternating strips of different crops along natural contours
terracing
produced level areas and reduces soil erosion
Steps involved in soil reclamation
1. stabilizing the land to prevent further erosion
2. restoring the soil to its former fertility
compost
a natural soil and humus mixture that improves both soil fertility and soil structure
mulch
mulch discourages the growth of weeds and helps keep the soil damp
shelterbelt
a row of trees planted as a windbreak to reduce erosion of agricultural land
agroforestry
concurrent use of forestry and agricultural techniques on the same land area to improve degraded soil and offer economic benefits
The Soil Conservation Act
of 1935 authorized the formation of the Soil Conservation Service
its mission: to work with the US citizens to conserve natural resources on private lands
Food Security Act (Farm Bill)
of 1985 contained provisions for two main soil conservation programs, a conservation compliance program and the Conservation Reserve Program
requires farmers with highly erodible land to develop and adopt a 5 year conservation plan for their farms that in
Conservation Reserve Program (CRP)
in a voluntary subsidy program that pays farmers to stop producing crops on highly erodible farmland