GEOG 3110 Lecture Notes - Lecture 20: Intermediate Disturbance Hypothesis, Exponential Distribution, Understory
17 Feb 2016
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Document Summary
Humans are also a cause of disturbance logging. Evidence from tropical rainforest: not well adapted to disturbance shade long live species, germinate well in organic soils. Maximum diversity occurs when members of both groups occur. Cumulative time-since last fire is called a landscape survivorship distribution. Time since last fire distributions often fit by negative exponential curve: Negative exponential distribution is a straight line when plotted on semi-log paper. The slope of the line gives the disturbance cycle. x-axis: year, y-axis: cumulative proportional area. Changes in slope indicate changes in disturbance cycle. (no straight line or several straight lines). All landscapes are the product of 2 or more different disturbance cycles. Almost everywhere we look we see changes. Old-growth is any stand much older than typical for a region or older than the region"s average natural disturbance interval logging companies use the steepest slope so they can cut the most timber. Old growth features trees around 150 or 200 years.
