ENV 1305 Chapter 7 notes
ENV 1305 Chapter 7 notes ENV 1301
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This 4 page Class Notes was uploaded by Hannah Fretheim on Sunday October 9, 2016. The Class Notes belongs to ENV 1301 at Baylor University taught by Dr. Larry Lehr in Spring 2016. Since its upload, it has received 6 views. For similar materials see Exploring Environmental Issues in Environmental Science at Baylor University.
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Date Created: 10/09/16
Chapter 7 notes Amount of primary production impacted by: - Climate- more primary production in places with lots of water and sunlight where it is not too hot or too cold - Number of species (species richness)- more diversity usually means more primary production because different plant species can benefit each other - Soil fertility- amount of nitrate and how well plants can retain it - Nitrogen cycle Nitrogen cycle: 1. Nitrogen fixation- bacteria convert Nitrogen from the air into ammonia (and ammonium) 2. Ammonification- decomposers break down dead things and release ammonia ions 3. Nitrification- ammonia and ammonium ions become nitrites and then nitrates, bacteria convert 4. Nitrogen assimilation- ammonium and nitrate ions are absorbed by plants and become organic compounds 5. Denitrification- nitrates are converted back into a gas form by bacteria 6. The weathering of sedimentary rocks can add nitrogen to the nitrogen cycle Terrestrial harvest systems: - Farming o temperate forest and temperate grassland biomes, o Mediterranean and prairie regions can have farmland but irrigation is required - Forestry o taiga and coniferous forests are the best for forestry o tropical biomes are good for plants, but the wood cannot be harvested as much because they replace themselves slowly - Ranching o is possible in every biome, but sometimes requires irrigation and are less sustainable o temperate grasslands seem to be the best Layers of Soil: - O horizon- very top layer, lots of organic matter - A horizon- also called topsoil, contains some organic matter, important for plant growth o Sand, silt and clay can exist in different proportions, determining the soil texture, soil that contains roughly equal amounts of all three and is ideal for farming is called loam - E horizon- only exists in some soils which are well-developed, contains sand and silt left over after clay and organic matter move downward - B horizon- contains material that moved down from the E horizon, “subsoil” - C horizon- lowest layer of soil, contains parent material that the soil developed from - R horizon- bedrock underneath the soil Development of soil- - Not all soils contain all layers - More layers build up over time o A, C and R are present in newer soil once organic matter has been added, forming the A horizon o Later, the A and B horizons separate when certain materials go down and the O layer forms on the top o In certain conditions, soil develops the E horizon and the higher layers go deeper - Impacted by climate, organisms, parent material, topography and time o Climate- influences weathering and the organisms that live in the area, precipitation leads to erosion o Organisms- provide nitrogen Problems with farming: How do we allow for a lot of food to be grown without the excessive use of pesticides, fossil fuels to power tools and other harms to the environment? Monocultures vs. polycultures- large amounts of one crop vs. multiple crops together - Pesticides and fertilizers allowed for monocultures and more crop growth - Borlaug- helped breed plants to have traits which helped them survive, increasing food production around the world Soil depletion - Erosion- a natural process, but we can speed it up which depletes the soil o When forests are cut down or soil is used in agriculture, it is eroded o When topsoil is eroded, minerals, nutrients and organic matter are lost o Conventional-tillage agriculture can lead to erosion by leaving soil exposed to wind and water o Overgrazing also exposes and disturbs topsoil which can lead to both erosion and desertification Deforestation - Deforestation in Southeast Asia o Loss of timber and building materials o More erosion - Clear-cutting- clearing whole areas of trees at one time, it disturbs the soil and causes more erosion - Slash and burn- trees are burned and the land is turned into farmland, the practice lacks stability because the soil eventually loses fertility - Sometimes fire prevention leads to larger fires which are more harmful to forests and soils than smaller fires Irrigation - Uses up large amounts of surface and groundwater o Losing water sources threatens biodiversity - Lots of water can be wasted through evaporation - Waterlogged soil- water table is at the very top of the soil which keeps plants’ roots from getting enough oxygen - Salinization- happens when salt builds up in the soil as a result of too much irrigation, the salt build up ruins the soil Pesticides - Do not only threaten pests, but also the health of many other species, including humans - Eventually, species evolve to be resistant to certain pesticides, making pesticides less effective in the long term - Pesticides are very costly Genetically modified crops - GMOs have had at least one outside gene added to their DNA in order to give them more desirable traits o Transgenic organisms- have a gene inserted from another species i.e. a gene from the bacillus thuringiensis bacteria has been inserted into corn to keep insects from feeding on it - Benefits o Can cause more crops to be produced o Can control for pests without having to use chemicals o Can produce crops that are especially beneficial to humans Golden rice- good source of vitamin A which can help those with vitamin A deficiency o Improved soil health - Controversy o Pests and weeds could become more resistant and therefore, easier to control o More monoculture plants present a higher risk of being destroyed by pests o Biotechnology companies can take control and profits away from farmers o Some are worried that they are a danger to human health- although studies that have been conducted have found no danger, it is possible that conflicts of interest have hurt the accuracy of these studies o Some people see changing the genetic makeup of organisms to be problematic because it is “unnatural” o Some believe genetically modified products should be labeled Solutions - Saving money by supporting local farmers around the world instead of importing produce - Increasing genetic diversity of crops o Crop rotation o Intercropping - Tilling crops in sustainable ways o Soil erosion is decreased by tilling across the slope of the land o Terraces can be built in steep terrain and windbreaks can be built in windy areas o No-till and low-till agriculture can decrease soil disturbance and erosion - Organic farming- growing crops without using pesticides, GMOs or synthetic fertilizers - Controlling the amount of livestock grazing that takes place on one area of land o Sometimes “resting the land” by keeping livestock off of it for a certain period of time can restore the land - Find ways to reduce damage to soil and ecosystems while harvesting forests o Shelterwood harvesting o Selective logging o Thinning the understory to prevent large fires - Improve irrigation methods o Using water efficiently o Decreasing the amount of water needed o Using mulch to reduce evaporation o Making sure soils are well drained to reduce salt build-up - Integrated Pest Management o Attempts to find a sustainable way to control pests o Leaving a small number of crops that are not pest resistant is one method o Switching back and forth between herbicides can help with weed control
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