7th Weekly Notes The Environment
7th Weekly Notes The Environment ENVT 0845-005
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This 3 page Class Notes was uploaded by Katrina Salamon on Sunday March 13, 2016. The Class Notes belongs to ENVT 0845-005 at Temple University taught by Dr. Udoeyo in Winter 2016. Since its upload, it has received 20 views. For similar materials see The Environment in Professional Education Services at Temple University.
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Date Created: 03/13/16
March 7, 2016 Agroecosystems Energetics: the way energy is transferred from one level of production to the next level Harvest index—the foods that are useful (or parts of food) that are used. Part of the food. The fraction of the total production that is usable o This consumed energy is stored as biomass Trophic level efficiency for domestic animals is usually more than 10% (worse efficiency than wild animals) Secondary consumers (meat eaters) are very costly, and make huge environmental impact. Nutrient cycling: o Agroecosystems are prone to nutrient loss due to Harvesting, which causes nutrients to decline and diminished primary production (removing biomass from the system) Constant soil disturbance (“continual disturbance”, which makes the soil much more susceptible to erosion) Irrigation removes huge amounts of nutrients from the soil Low biodiversity, comprised of just a few species The Growth of crop plants o Crops use photosynthesis in order to grow and reproduce Needs light, water, carbon dioxide, and the essential nutrients, nitrogen, phosphorus and potassium The growth of crop plants o Plants sotre carbohydrates, proteins, and oils o Parts of the plant: Leaves Stem Roots Fruits Determination of possible crops by climate and soil Tropical and temperate zones are most agricultural Plants vary in soil, water, and temperature needs Crops are also influenced by surrounding organisms o Bees and other organisms pollinate o Worms, bacteria, insects, fungi recycle nutrients o Pests and pathogens Soil o Made up of minerals, organic matter, water, air, and organisms o Sand: particles 0.052 mm, chemical structure resembles parent material o Silt: particles 0.002.5 mm o Clay: particles less than .002 mm Soil horizons: layers of the soil O Horizon: humus: leaves or crop residues A Horizon: mix of organic matter and minerals B Horizon: subsoil rich in clay from sand and silt Soil fertility: ability of soil to support plant growth Determined by soil characteristics—many nutrients in the soil are not in a form plants can use, so they have to be converted o There must be availability of the same 3 key elements (nitrogen, phosphorus and _______?) o Clay tends to increase soil fertility o Hugh rates of evaporation cause salts to accumulate in desert soils (pH in desert may reach 9) o Amount of Aeration: ability of oxygen and carbon dioxide to diffuse into and out of the soil o Soil aeration is directly related to tilth (: physical arrangement of soil particles that facilitates aeration, seedling emergence, and the growth of roots) Soil conservation Agtoecosystems lack many of the processes that maintain soil fertility o Accumulation of topsoil o Plants leaves and stems help prevent erosion by blocking/buffering water fall with leaves and holding the soil in place with roots Water is essential: water level determined by soil type/factors and rainfall Soil texture determines how much water it can hold Field capacity: the water’s ability to hold water against the upward pull of water Wilting point: situation where the soil is not able to hold water because there is no water there (not watered or no rainfall) Irrigation: a system of water diversion and conducting it from one area to another, used for 5,000 years Potential Evapotranspiration (PET) March 9, 2016 Conserving water in Agroecosystems Conserving water is necessary for any ecosystem Scientists have come up with methods of managing water in agriculture o Drip irrigation o Developing new breeds of plants that use less water o Planting alternative crops (like Jojoba) Domestic animals 20% earth’s pasture for animals 30% cropland for animal feed (the land we should be using for crops is being used for animal feed) trophic level efficiency can be even higher than the normal 10%. It depends on the source of food and level of activity. Eating high trophic level food can increase fat content. Most domestic animals are herbivores Efficiency depends on ability to break down cellulose A pasture can support twice the number of cattle than horses More environmental impact o Waste management o Manure is rich in nutrients but there are pathogen and methane creation concerns o Energy production from waste—burn animal feces to produce electricity o Air and water pollution, greenhouse gasses (methane) o Land use—forests and habitats cleared for grazing o Transmission of disease o Impact to human diets Genetically modified organisms o We depend upon genetically modified organisms, plants and animals o They are more productive from breeding hybridization and cloning, but it decreases genetic diversity o Efforts to maintain and improve genetic diversity is ongoing o Amaranth can resist pests Genetically modified organisms develop new varieties by taking a gene from the cells of one species and inserting it into the cells of another to improve yields, disease and pest resistance, addition of nutrients, etc. This is still very controversial. Managing competitors and pests o 42% of all crops are lost to pests and disease o Chemical pest control—effective, but threatening to health. (DDT) o Biological pest control—use of predators and parasites to control pests Diet determines significant portion of ecological footprint Meat consumption increases size of footprint “food miles”—how far food has to travel to the consumer processing and storage organic food is encouraged SO: eat plants, local, fresh, seasonally, sustainable products This will enable future generations to live sustainably Care must be taken for soil and water as well as habitats Chronic hunger affects 10% of people in the world Nutrition around the world as well as in the United States is a growing problem Gov’t must create sustainable food industry
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