{ "cells": [ { "cell_type": "code", "execution_count": 1, "metadata": { "tags": [ "remove-cell" ] }, "outputs": [], "source": [ "import sys\n", "import os\n", "if not any(path.endswith('textbook') for path in sys.path):\n", " sys.path.append(os.path.abspath('../../..'))\n", "from textbook_utils import *" ] }, { "cell_type": "code", "execution_count": 2, "metadata": { "tags": [ "remove-cell" ] }, "outputs": [], "source": [ "import plotly.figure_factory as ff" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "# Example: Wind-Damaged Trees \n", "\n", "In 1999, a huge storm with winds over 90 mph damaged millions of trees in the [Boundary Waters Canoe Area Wilderness](https://www.fs.usda.gov/visit/destination/boundary-waters-canoe-area-wilderness) (BWCAW), which has the largest tract of virgin forest in the eastern US. In an effort to understand the susceptibility of trees to wind damage, a researcher named [Roy Lawrence Rich](https://www.proquest.com/docview/305463532?pq-origsite=gscholar&fromopenview=true) carried out a ground survey of the BWCAW. In the years following this study, other researchers have used this dataset to model _windthrow_, or the uprooting of trees in strong winds." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "The population under study are the trees in the BWCAW. The access frame are *transects*: straight lines that cut through the natural landscape. These particular transects begin close to a lake and travel orthogonal to the gradient of the land for 250–400 meters. Along these transects, surveyors stop every 25 meters and examine a 5-by-5-meter plot. At each plot, trees are counted, categorized as blown down or standing, measured in diameter at 6 ft from the ground, and their species recorded. " ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "Sampling protocols like this are common for studying natural resources. In the BWCAW, over 80% of the land in the region is within 500 meters of a lake, so the access frame nearly covers the population. The study took place over the summers of 2000 and 2001, and no other natural disasters happened between the 1999 storm and when the data were collected. " ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "Measurements were collected on over 3,600 trees, but in this example, we examine just the black spruce. There are over 650 of them. We read in these data:" ] }, { "cell_type": "code", "execution_count": 3, "metadata": {}, "outputs": [ { "data": { "text/html": [ "
\n", " | diameter | \n", "storm | \n", "status | \n", "
---|---|---|---|
0 | \n", "9.0 | \n", "0.02 | \n", "standing | \n", "
1 | \n", "11.0 | \n", "0.03 | \n", "standing | \n", "
2 | \n", "9.0 | \n", "0.03 | \n", "standing | \n", "
... | \n", "... | \n", "... | \n", "... | \n", "
656 | \n", "9.0 | \n", "0.94 | \n", "fallen | \n", "
657 | \n", "17.0 | \n", "0.94 | \n", "fallen | \n", "
658 | \n", "8.0 | \n", "0.98 | \n", "fallen | \n", "
659 rows × 3 columns
\n", "\n", " | diameter | \n", "storm | \n", "
---|---|---|
min | \n", "5.0 | \n", "0.02 | \n", "
25% | \n", "6.0 | \n", "0.21 | \n", "
50% | \n", "8.0 | \n", "0.36 | \n", "
75% | \n", "12.0 | \n", "0.55 | \n", "
max | \n", "32.0 | \n", "0.98 | \n", "