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Lecture 44

GEOG 1280 Lecture 44: Lecture 44

3 Pages

Course Code
GEOG 1280
Bruce G.Erickson

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o82 The Uniformitarian Principle: the present is the key to the past The Principle of Limiting Factors: if rainfall is the most limiting factor, then the amount of wood produced by a tree in any single year will reflect mostly the amount of rainfall that fell within that year. You look for sensitive vs. complacent treering growth Sensitive tree growth have: o High degree of annual variation o Wide and narrow rings intermixed through time Limiting growth factor (e.g., rainfall or temperature) are highly variable year to year Especially true for harsh sites (steeprocky for moisture sensitivity, treeline for temperature) Matching patters of relatively wide and narrows rings across trees is easier when ample variation exists. Oldest trees are bristlecone pine trees: grow in dry and cold environments (small widths of rings) Pando: trembling aspen tree colony in Utah, clones itself via a root system (80,000 yrs old) Spruce tree in Sweden: 9500 yrs old, due to cloning. Crossdating Overlapping of living tree samples, dead wood samples and dendroarcheological samples to reach an older age. Why is dating so important? The Past Glacial Periods On land 4 glacial advances were recognized. Glacial and Interglacial (Warm) Periods Wisconsin Glacial Sangamon Interglacial Illinoian Glacian Yarmonth Interglacial Kansan Glacial Aftonian Interglacial Nebraskan Glacial Milankovitch: orbital changes of the earth around the sun affects the amount of radiation
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