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Canada (161,660)
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GGR107H1 (52)
Chapter 4

Chapter 4: Soil & Agriculture

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Sarah Wakefield

CHAPTER 4 SOIL AND AGRICULTUREMer Bleue Conservation Area a provincially protected wetland area located in Ottawa Ontario classified as a wetland site of international importanceHosts a number of unusual plant species that are adapted to boggy and acidic conditionsThose plant species are sphagnum moss bog rosemary blueberry cotton grass cattails and tamarackThe wetlands provide a specific type of soil peat which has occurred due to the last ice ageCanada has the most extensive peat lands in the world covering 14 of land areaBogs which are 6m deep took 8000 years to formPeat lands are natural carbon reservoirs and hold 13 of the carbon stored in soils Through decomposition peat releases soil gasses which function as GHGs in the atmosphere and warming can lead the peat to release these GHGs at a faster rate and result in positive feedback Storage of carbon in peat depends on the balance between production and decompositionPlants storesequester carbon due to photosynthesisStored carbon accumulates in peat through plant litterTemperature and light influence the amount of carbon stored in the soil The study of soil enables scientists to understand how soils behave in a global context especially climate change 41 SOIL AS A SYSTEMSoil in everyday language means dirtSoil is not merely composed of rocks it is composed ofDisintegrated rocksOrganic matterWater GassesNutrientsMicroorganisms The composition of soil is half mineral matter and half organic matter with spaces holding air water and soil gassesThe organic matter is deadliving microorganisms and decaying matter from plants and animals One teaspoon of soil can hold100 million bacteria500 000 fungi100 000 algae50 000 protists Soil provides habitat to earthworms insects mites millipedes centipedes other invertebrates and burrowing animalsSoil is part of the ecosystem 411 SOIL FORMATIONSoil formation occurs in the lithosphere surface of earth where the parent material is exposed to the effects of the atmosphere hydrosphere and biosphere Parent material The base geological material in a particular locationLava or volcanic ashRock or sediment deposits by glaciersWindblown dunesSediment deposits rivers lakes oceansBedrock mass that makes up earths crustWeathering erosion and deposition Weathering The physical biological and chemical processes that break down rocks and minerals turning large particles into smaller onesPhysical weatheringBreaks down rocks without chemical change to parent materialRain and wind are the primary forces of weatheringDaily and seasonal temperatures affect expansion and contraction of parent materialWater freezes and expands rocks causing cracks Chemical weatheringWhen water and other chemicals interact with the parent materialWarm and wet conditions accelerate chemical weatheringHappens in acidic conditions bogs Biological weatheringWhen living things breaks down parent material physically or chemicallyTree roots rubbing against rocksDecomposition of leaves and branches creates chemicalsChemicals from roots release chemicals ErosionMovement of soil from one area to anotherErosion promotes physical weatheringCan happen from wind and waterUsually in dry places with no vegetation Organic matter creates humusThe soil at Mer Bleue is called peat as it is compressed organic matter Soil formation table pg 76 fig 41
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