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School of Environment

Environmental Ecology: Patterns of Climate change and climate variation, and is focused mostly on the surrounding area in Ontario, for relevancy to the course. Ecology of planet earth Human influence Biochemical Cycles Terrestrial production and decomposition Global warming and Climate change September 10 : Deep geology Ice ages- consequences of ice ages on Canada and Ontarios geomorphology Canadian Shield The Canadian Shield is dated back to the Precambrian time and before organisms appear. It is the worlds largest area of Precambrian bedrock. Its continuous and stayed together as an un- encroached landmass even when continents shifted. The Canadian Shield is also called the Laurntien shield The shield is low in altitude- 300m to 600m in elevation and around 1500m in Baffin and Labrador. Nutrients are low because its old and many have been leached away from plants, and eroded away from glaciers. The soils derived from this rock are very poor. The round Mountains of the Georgian Bay prove how glaciers affect the earth, they are very erosive. The first anaerobic life, which was bacteria, started in the Water, so that it was protected from the suns UV rays. The bacteria make use of the water, CO2, sunlight and the build up of oxygen, which was released into the atmosphere via evaporation. Stormatolites are the earliest life form. No photosynthesis happened before 3.5 billion years after the big bang. The first record of oxidized iron in rock was 3.5 billion years ago. The first photosynthetic releases happened during this time also. All the free O2 was absorbed by the ocean or seabed rock. At about 2 billion years ago first O2 was released in to the atmosphere and absorbed by the land surface. The accumulation of O2 in the atmosphere, the zone lakered formed and life start on land. 80% of the atmosphere is Nitrogen and 20% is oxygen and many other gases. The forming of the ozone because of the o2 build up traps heat in the troposphere (10km) changing earths climate from -18 to 14. 1. Hadean 4500 MYA- 3800 MYA 2. Archean 3800 MYA to 2500 MYA, about 3000 MYA was when algae was first found. 3. proterozoic 2500 MYA to 500 MYthis is at the beginiing of the Cambrian exploision of life. A during this time there was a great diversification of fauna, then fish, then multi-celled plants, amphibians and reptiles. 4. phanerazoic 500 MYA to present During the Triassic birds and dinosaurs evolved. There was also the destruction of these animals in the late crustaceous and the evolution of humans occurred during the Holocene. Ices ages: 1. The Quaternary glaciations. This was 1 of 4 glaciations This one occurred in the Precambrian along with another The other 2 were in the panerozic- one ~240 MYA and the other less than 1.6 MYA The temperature fluctuations that the glaciers produced allowed us to tell when they occurred, by using the benthic oxygen 18 (per mil) method Early studies suggested 4 major glaciations. Too simple. Now we know that ca. 14 glaciations. The temperature fluctuated a lot between 6 million years ago until now, and we are now coming to the end of an interglacial period, but in actual theory were not. Why do glaciations occur? 1.Milancovitch Cycles: He came up with the Astronomical theory of climate change: Orbital parameters trigger climate instability in the Quaternary. How far away from sun, angle amount of solar radiation (energy) Three important parameters: Eccentricity: this is when the earths cycle around the sun changes and becomes more or less elliptical. When the earths orbit is farthest from the sun its called aphelion, when it is cloes its perihelion. It takes 100,000 years to chage the orbit of the sun from one extreme to another. Obliquity: this is the tilt of the sun towards the sun it also changes, this take 40,000 years to shift.. Precession: This is the wobble of the earths orbit, this takes 20,000 years to shift. a. All three together maximally far away, cold angle glacial period, High degree of eccentricity (increases seasonality), minimum tilt/obliquity, Northern hemisphere summer at aphelion (cooler summers). b. All three together maximally close, warm angle interglacial c. But: Milancovitch cycles existed also in Tertiary, why no ice ages? Despite all this, the exact mechanism for major ice sheet growth is still unclear 2. Change of sea currents: this occurred because of the closure of the sea way between north and South America. The build up of the Island in SA closed the circulation of the panama (hot) current and moved it up into the Pacific Ocean. This had a large effect on the glaciations periods 3. Mountain build-up: this created a change in the albedo of the earth. The used to be a lowland and there were high amounts of the lowland vegetation. Only 10-45% of the sunlight was reflected back into our atmosphere. When the tertiary mountains were created the mountains created a feedback loop of high albedo where they reflected 90-95% of the solar radiation The last Quaternary glaciations were the Wisconsin glaciations in North America. This ice age created the great lakes. In the middle o f the glacier the ice was almost 4km deep, and 2-3 on the edges. Ice sheet thickness during the last Glacial Maximum (Wisconsin Glaciation) was as deep as 3,000 m and ice flowed from the interior to its margins. More 1000m thick ice covered Southern Ontario. The development of the great lakes was from the carving of the glaciers advancing and retreating. The glacier scoured the ground. There was also the encroachment of sea water. The retreat of the glacier created the isostatic uplift. This is when the depression of the earth because of the heavy glacier is rebounding. At Hudson Bay the earth rebounded by 280m. Toronto is still lifting about 3mm per year. Glacial Till: till is all the material thats being pushed by the flow of the glacier. Its permeable and loose as well as nutrient rich. Till is also known as moraines. Oak ridges moraine is the closest to Toronto. Ice sheet split, 15,000 ybp its an interlobate moraine Drumlins: These are glacier marks also, and it tells use, which way the glacier is moving. At one end, theyre pointy and high the other end is smooth and round. Periglacial landscapes: these are the landscapes in front of glaciers and it is inhabitable.. There tends to be a lot of silt known as Loess. This loess is gets blown away from the glacier by strong winds off the icecap and transports and deposited on land surface. Fine silt is <0.2mm Loess is very fertile and nutrient rich because it hasnt been seeped from its nutrients. The Effects of Wisconsin glaciations Almost all life was reset to 0! Rebound of: water systems? soils? life? th September 15 : the ecological history of Ontario 2 The consequences of Ice ages on CA and ON: Wisconsin glaciations: Almost all life was reset to 0 There was massive primary succession. The build up of soils is needed, and the glacial till is deficient in Nitrogen, organic matter, structure and water retention, and animals had a hard time colonizing the areas where the glacier once was, also the periglacial areas. How did the species return? The south of Florida was an area that wasnt touched by the glacier. There was a Refugio for the eastern species. The species diversity declines as we move out of the south of Florida. The tundra is where it is the lowest. Re-establishment of Ontarios forests SOntario, ice-free since 9000 years and there were migrations over several 1000 km. It is depenant on 4 major factors: 1. Forest dynamics (competition between tree species) Example: o shade tolerant species vs. shade intolerant. o Fast growing vs. slow growing. o Early vs. late successional species. o Germination requirements gaps vs. closed canopy). o Arrival at a given geographic location? 2. Factors external to forests (climate change, disease) o July Ts 3C cooler 12 000 y BP, 2C warmer 9000 6000 y BP, equal since 3000 y BP o Up until 4700 y BP, hemlock was much more dominate, and then crashed within +- 100 y insect-related disease? Recovery can be slow. o American chestnut vs. imported chestnut blight. American chestnut made up to (60- 70%) of all trees and now it is almost gone; only 100-150 reproducing trees remain. The imported chestnut is form Asia and we are also currently loosing Elm, Ash, Beech and Hemlock 3. Soil development The first colonizing wave was the conifers because of the acidification of the soil. This was because of the strong interaction with the un-weathered parental bedrock. Then deciduous trees colonized when the soil was less acidic and
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