Biometry
Stat 412

Field Assignment #1: Basic Sampling Methods

Purpose: Collect data for basic statistical analysis and graphing

Equipment needed: (for 50 students)

5 – 100 ft transects
5 - writing slates w/pencil
25 - data sheets
5 - random number tables

Problem:

1. There are a number of tree stands on campus, with Douglas Fir (Pseudotsuga menziesii) being one of the largest and most dominant species in these stands. See below for identification.
2. The goal of this study is to compare the size of Douglas Fir trees, as measured by their circumference at breast height (1.4 m), between different stands on campus.
3. We will conduct the study by collecting data from two different tree stands on the WSU campus using a random sampling procedure.

Procedure: Surveyors will be divided into five groups of 10 people/group.

1. Transects will be deployed through the stand at randomly chosen intervals. Record the maximum length of the transect.

2. Each team should generate a set of random numbers using the random number sheet (n=10) that range within the maximum lengths of the transect. Record these numbers on the slate for each group.

3. Using the list of random numbers locate the coordinate on the list and locate the nearest tree to that coordinate (nearest neighbor).
   If no tree is within 10 m, or if you encounter a previously measured tree, skip to the next transect coordinate.
   Measure the circumference of the tree at the height of your chest and record the number on your data sheet.

4. Collect data on a total of n=30 trees per team, rotating the roles of the different team members in your group.

5. After we survey one area of campus we will then move to another area to take a second group of samples.

IMPORTANT: At the end of the survey glance over your data sheet and make sure all of your numbers are readable. Do not leave the study area until you have done this! Return data sheets to the instructor.

Identification of Douglas Firs Trees:

Needles are yellowish-green, 1-inch-long and arranged in a spiral around the branchlets, like a bottlebrush.

Bark on young trees is thin, smooth, and gray, with numerous resin blisters. On mature trees the bark is thick (4 to 12 inches) and corky.