Wisconsin TIGER 2.1 Manual

TIGER for Stratified SamplingTM 1.0:

the Quick Read User’s Manual for All States

CWM Software, L.L.C.

General Information

The computer program called TIGER for Stratified SamplingTMand all of its variants, this manual, and the TIGER for Stratified SamplingTM1.0: the User’s Manual for All Statesare copyrighted by CWM Software, L.L.C.TIGER for Stratified Sampling and thismanual have been adapted from TIGER for Woodlands and Compartments, developed by CWM Software, L.L.C.

The license agreement, which must be accepted for any variant of TIGER for Stratified Sampling to run on your computer, explains your rights and responsibilities as all TIGER for Stratified Samplingusers.

Limitation of Liability

Neither CWM Software nor anyone involved in the creation, production, or delivery to you, shall be liable to you for any damages, such as lost profits, lost savings, or other incidental or consequential damages arising out of your use or inability to use the program (all variants of TIGER for Stratified Sampling) or the breach of any warranty.Some states do not allow the limitation or exclusion of incidental or consequential damages, so the above limitation may not apply to you.

Suggestions

If you have suggestions or comments about TIGER for Stratified Sampling, please contact or CWM Software, c/o Jeremy Mize,2503 H Avenue, Williamsburg, IA52361.

TABLE OF CONTENTS

Page

GENERAL INFORMATION ii

TABLE OF CONTENTS iii

INTRODUCTION 1

HOW TO TAKE A STRATIFIED SAMPLE 3

HOW TIGER FOR STRATIFIED SAMPLING WORKS 7

OPERATION OF TIGERFORSTRATIFIED SAMPLING 7

Using TIGER SS menus 7

Woodland data – how to enter them 12

Stumpage rates – how to enter and change them 12

Volume and weight estimation systems – how to enter and use them 13

Analyzing woodland data for traditional inventories - how to do it 13

Analyzing woodland data for 100% inventories - how to do it 15

Economic analyses - how to do them 16

Setting options (defaults) 17

HOW TIGERFOR STRATIFIED SAMPLING

ESTIMATES PER ACRE CHARACTERISTICS 17

HOW TIGERFOR STRATIFIED SAMPLING

ESTIMATES GROWTH AND MORTALITY 20

HOW TIGER SIMULATES THINNING A WOODLAND 21

HOW TIGER FOR STRATIFIED SAMPLING ESTIMATES

WOODLAND CHARACTERISTICS 21

ECONOMIC ANALYSES DONE BY TIGER FOR STRATIFIED SAMPLING 22

LIMITATION TO TIGER FOR STRATIFIED SAMPLING 24

BIBLIOGRAPHY 25

APPENDIX IInstalling TIGER for Woodlands and

Compartmentson your computer 27

APPENDIX II Volume and weight estimation systems used by TIGER

for Stratified Sampling 27

INTRODUCTION

This manual is an abbreviated version of the TIGER for Stratified SamplingTM 1.0: the User’s Manual for All States.It is called the ‘quick read” version because you should be able to read it much more quickly than the other version.This manual will introduce you to the program and how it works.If there are particular parts of this manual that you want to understand better, go to the other version and look for the name of the section you are reading in this version.This version was developed by starting with the longer version and deleting lots of words and figures to leave the basics and adding some writing, so it flows smoothly.

Few woodlands are composed of just onearea covered by a homogeneous forestin which the species composition, age structure, number and size of trees per acre, and forest history are relatively uniform across the whole area.Instead, they are composed of two or more areas that are occupied by trees that differ from each other in species composition, age, number of trees per acre, and/or maybe other characteristics.

For a woodland that is not homogeneous and is composed of two or more distinct forest types, taking a simple random or systematic sample of the woodland will NOT produce the required information needed to decide if management activities are needed for any of the forest types in the woodland.

Stratified sampling is a sampling method that involves dividing a population, in this case a woodland, into relatively uniform, non-overlapping areas, often called compartments or stands or strata in statistical jargon.To do a stratified sample, you first need to divide the woodland into compartments and then take a simple random or systematic sample of each compartment.Because a sample is taken from eachcompartment, you can estimate the characteristics of interest for eachcompartment by analyzing the measurements for the compartment and use that information to decide what management activities are neededfor the compartment.

TIGER for Woodlands and Compartments (TIGER WC) is a computer program that will analyze inventory data from a random or systematic sample and produce results that you can use to decide what management activities are needed if the inventory data are collected on individual compartments.The program allows you to capture data collected in a traditional inventory using fixed area plots or variable radius plot sampling (prism) or data collected in a 100% inventory data in which all trees that meet some criteria are measured.TIGER WC cannot combine data for compartments to estimate overall characteristics of a woodland.

TIGERSS[1] (short for TIGER for Stratified Sampling) is a computer program that willcombine data collected in a stratified sample of a woodland and estimate characteristics for the entire woodland or at least the portion of the woodland sampled, which will be referred to as the woodland, even if only a portion of the woodland is sampled.TIGER SS allows you to simulate the impact of managing up to 15 compartments in which each compartment can have a unique management activity, including no management.

TIGER SS is a program that could be useful for a consultant who wants to estimate the overall condition of a woodland to develop a complete management plan for a client.It will process both traditional and 100% inventories on a woodland, although it will not process them together.

TIGER SS willcombinetraditional inventory data that were collected using simple random or systematic sampling on up to 15 compartments andi) estimate the initial, at the time of measurement, volume or weight and value of timber on the combined compartments, ii) simulate a variety of types of thins, such as diameter limit and species elimination, on any or all compartments that you wish to simulate thinning and estimate the volume or weight and value of the material that would be removed from and would remain in the woodland, iii) simulate the growth of each compartment (as inventoried or after a simulated thinning) 5, 10, 15, and 20 years after the inventory was done, iv) estimate the future volume or weight and value of the woodland, and v) compute appropriate economic returns.The values for each compartment are combined to develop estimates for the entire woodland using traditional formulas for stratified sampling (Avery and Burkhardt 2002, Shiver and Borders 1996).

TIGER SS will also combine 100% inventories for up to 15 compartments and estimate the total number of trees, the total volumeor weight and value, and the basal area per acre by species and for all species based on measured trees in each compartment.As mentioned above, the analysis of 100% inventory data is limited as growth cannot be estimated, so no values over time can be estimated.

This manual covers all states for which a variant of TIGER SS has been developed: CT, DE, IA, IL, IN, MA, MD, ME, MI, MN, MO, NH, NJ, NY, OH, PA, RI, WV, VT, WI.

The next section gives a brief introduction to doing stratified sampling of woodlands.The following section gives an overview ashow the program works.Following those sections are others that describe how the volume or weight and value per acre for compartments are estimated, the modelsused to estimate growth and mortality of the trees in each compartment, how thinning of compartments is done, how woodland characteristics are estimated from compartment estimates, the two types of economic analyses that can be done, limitations of the program, acknowledgements, and the bibliography.After that is Appendix I, which describes how to install TIGER SS on your computer, then Appendix II, which lists the names of the volume and weight estimation systems used by TIGER SS.

HOW TO TAKE A STRATIFIED SAMPLE

I am going to present a quick overview of how to take a stratified sampling of a woodland.This will be an introduction if you know nothing about stratified sampling or a review of some key points if you have studied the method.I recommend you learn more about stratified sampling to help you use it efficiently (Avery and Burkhardt 2002; Shriver and Borders 1996; and various internet sources).

To get started, I will present a brief review of how to do a forest inventory (stratified or not) (Avery and Burkhardt 2002).The 8 points below are an abbreviated version of Appendix VII in TIGER for Woodlands and Compartments 2.0: the User’s Manual for All States.The 8 points explain the basic organization of any forest inventory and are a good basis for discussing stratified sampling.

i) Purpose:Why do you need to do an inventory?What will you do with the information you get?

ii)Background information:Are there any past inventories of the area, which can be very helpful for identifying how much work will need to be done?Are there aerial photos?

iii)A clear identification of the area to be inventoried:Is it the whole woodland or just a portion (a compartment or some compartments)?How many acres are there and how accessible are they?

iv)Information required from the inventory:Decide what specific information needs to be estimated and in what form.

v)Design of the inventory:TIGER WC and TIGER SS work with small scale inventories, maybe 1 to 100 acres per compartment.Two distinctively different types of inventory - traditional (plot based) and 100% (all of a certain type of tree are measured) - can be done.

vi)Measurement procedures:For a traditional inventory with either fixed area or prism plots, the plots need to be located so trees can be measured.

vii) Compilation and calculation procedures:Before entering data into TIGER WC, someone should review each data sheet and make sure all necessary data have been collected.

iix) Reporting of results and storage of data:At a minimum, you will want to print and/or save the ‘Initial condition’ results.

If this abbreviated version does not seem elementary to you, I recommend you look at Appendix VII in full manual.

Now, l will get specific about stratified sampling.Points ii, iii, and v(above) deal with maps and identifying compartments.Given a map of a woodland, you need to divide it into non-overlapping areas (compartments)that will be inventoried and into areas that will not be inventoried, such as around a house, an agricultural field, or a pond.Aerial photos, obtainable from County Conservation offices in some states, are an excellent aid.

Part of point vdeals withcompartmentalizing your woodland: dividing the woodland into relatively homogeneous areas (compartments) based on species composition, stand age structure, stand density, and maybe stand history.Note: compartments are seldom VERY homogeneous, so there will be variation within compartments; that cannot be avoided.Some compartments are obvious, such as a 2 acre pine plantation in a mostly hardwood woodland.Compartments should not be very small, maybe 3 to 5 acres minimum, unless the woodland is quite small.

After developing a map that shows the boundaries for the compartments, you need to estimate the number of acres in each compartment.Given the acreage of each compartment, you need to decide how many plots to take and locate the plots on your map.The number of plots is always an important question that is not easily answered.Ashley (1978) wrote a classic article on sample size estimation, and I am going to use parts of it here to introduce you to the concept of deciding how many plots are needed for an inventory (Table 1).

A general management plan requires the least precise estimate because what might be called a ‘ball park figure’, which is not very precise (possibly 30 to 40% different from the exact value), is precise enough to develop a management plan. But if you are selling high-value timber, a low precision estimate, which would mean that the exact value is maybe 40% or 50% different from the average from a sample, could result in your losing a lot of money with a lump sum sale. To emphasize that point, Ashley (1978) suggests a 100% inventory for the veneer quality logs.

Table 1.Desired levels of precision for various inventory objectives(adapted from Ashley, 1978).

ObjectivePrecision

(2 standard errors)

General management plan.Basis for± 30%-40%

establishing future policies andplanning

procedures.

To establish cutting policy on sales.± 20%

Payment to be made byactual sale.

Lump sum sales -- pulpwood or other±10%

low-value products.

Lump sum sales -- fine hardwoods orother ±1%-5%

high-value products.Consider100%

inventory for veneer qualitytrees.

Real estate appraisals involving±5%

high-value timber

Court litigations±5%

The number of plots that you need to measure in an inventory depends upon the variability of the woodland and the precision desired.Ashley (1978) producedan array of measures of variability (the coefficient of variation) to estimate the number of plots to be measured to achieve various levels of precision (Table 2).As you can see, with low variation (30% for the coefficient of variation) and a wide desired level of precision (± 30%) a small sample is required.Note:the coefficient of variation (CV) is equal the standard deviation (referred to as S by statisticians) divided by the average (referred to as the mean by statisticians) then multiplied by 100 to convert it to a percentage.Ashley (1978) said that Midwest hardwoods stands have a CV near 60% and pine plantations are near 30%, and that should cover most of the range of CVs.

Aside from using Table 2, there are various rules of thumb for estimating sample size. A rule of thumb from a consultant in the Midwest is 1 plot per 2.5 - 3 acres for developing general management plans. For estimating basis, 1 plot per 4 - 5 acres is used and the stand is not compartmentalized. A recommendation from the Northeast is a minimum of 20 plots in an unstratified area.

Table 2.Sample size needed to achieve a desired level of precision as a function of coefficient of variation (Ashley, 1978).Note: Ashley recommends a minimum of 10 plots for all situations.

CoefficientDesired level of precision

of variation

(%)±5%±10%± 15%±20%±25%± 30%

30 144 36 16 9 6 4

40 256 64 29 16 11 8

50 400 100 45 25 16 12

60 576 144 64 36 23 16

70 784 196 88 49 32 22

I have used the terms random and systematic in relation to sampling and want to discuss them now.Stratified sampling can be done with randomly located plots and with systematically located plots.Random sampling has some theoretical benefits but is generally more difficult to do, although there are GIS systems that can locate plots randomly, which makes it easier.But, as a general rule, foresters use systematic sampling to locate inventory plots in a forest.

Note:Foresters often take systematic samples, which are usually analyzed as a simple random sample.In systematic samples, plots are systematically located across the area to be sampled, while plots for a simple random sample are randomly located.Analyzing systematic samples as if they were random is probably acceptable, particularly if the sampling lines run perpendicular to the terrain (Freese, 1983).

To systematically locate plots in a woodland or compartment, you create a series of parallel lines that are equally spaced across the woodland or compartment and establish a plot every certain distance along the lines.

Another approach is to sample from individual compartments.Run lines perpendicular to slope.If the shape is such that it is difficult to get enough plots by the time a line reaches the edge of a compartment, start another line at a bearing that will keep you in the compartment for a reasonable distance and continue on that line.

The simplest way to take systematic samples across multiple compartments is to select one distance between plots and apply it to all compartments.Sometimes you want to take more plots per acre for some compartments than others.To do this, you need to change the distance between plots from one compartment to another.This is certainly doable, but you need to be careful while doing it.

This is a very brief explanation of stratified sampling, and you need to get more information before doing it.At least it will give you an introduction to how it is done and some things to think carefully about before going to the woodland to actually establish and measure plots.

HOW TIGER FOR STRATIFIED SAMPLING WORKS

TIGER SS allows you to simulate the management of multiple compartments and combines the results of the analyses of each compartment to produce estimates of the condition of the whole woodland when you have done a traditional inventory of each compartment.It will also combine the results of 100% inventories done in multiple compartments to estimate total volumes or weights and values for the compartments inventoried.

TIGER SS was developed from TIGER WC. TIGER SS reads inventory data files that you must createby using TIGER WC, and it uses those files to produce a woodland data file.Having used TIGER WC to create data files for all of the compartments in a woodland, you can start TIGER SS and indicate you want to start a new woodland.As will be described later, you will need to enter four pieces of information about the woodland and then open the data files for all of the compartments in the woodland.Having entered the information and opened all of the compartment data files, you can save the woodland data file, which will contain the four pieces of information about the woodland and the data for all the compartments.

OPERATION OF TIGER FOR STRATIFIED SAMPLING

Using TIGER SS menus

After starting TIGER SS (see Appendix I for information on installing the program), you will see what is referred to as the startup screen.The Start Up window allows you to start a new woodland inventory, open a file for a woodland inventory, start a new stumpage rates file, or open a stumpage rates file.It also allows you to start an analysis which will only happen if you have startedentering woodland inventory data or opened a woodland inventory data file.

Before proceeding, you need to understand a few things about TIGER SS.As has been mentioned and will be explained in more detail later, TIGER SS does not allow direct entry of inventory data. You need to do an inventory for each compartment in a woodland, and the data have to be entered, one compartment at a time, into TIGER WC, which will create a data file for each compartment.Those files can then be used by TIGER SS.