Lecture 7Forestry 3218

Forest Mensuration II

Lecture 7

Forest Inventories

Avery and Burkhart

Chapter 9

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• Determine the value (volume, quantity) of resources in an area as accurately as available time and money will permit

• Requires:– Reliable estimate of the forest area (maps, air

photos, GIS databases)– Measurements of an unbiased sample of the

resources

Purpose of inventories

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General rules of thumb

• Intensity of sampling increases as the value of the resource increases

• Intensity of sampling increases as area covered decreases

• Intensity of sampling increases as risk of making a bad management decision increases

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Types of inventories

• Land acquisition– Surveys designed to evaluate the net volume and

value of merchantable trees– Timber quality information desired– Soil / site quality information may be desired– Distance to mills or other property you own or

manage would be of interest

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Types of inventories

• Timber sales:– Surveys designed to evaluate the net volume and

value of merchantable trees– Timber quality information desired

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Types of inventories

• Management planning– Surveys designed to evaluate the growth, yield,

and potential harvest of wood– Surveys designed to evaluate the condition and

change of multiple resources, such as wildlife habitat

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Types of inventories

• Special purposes– Insect and disease infestations– Regeneration surveys– Moose surveys– Bird surveys

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Inventory planning

1. Purpose of the inventory– Why the inventory is required– How the results will be used

2. Background information– Past surveys, reports, maps, photos– Personnel, budget, or time constraints

3. Description of area to be inventoried– Location, size, terrain, accessibility,

transportation factors

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Inventory planning

4. Information required from inventory– Tables and graphs– Maps– Outline of report

5. Inventory design– Identification of the sampling unit– Construction of the sampling frame– Selection of the sampling technique– Determination of the sample size

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Inventory planning

6. Measurement procedures– Location of sampling units– Establishment of sampling units– Measurements within sampling units– Recording field data– Supervision and quality control

7. Compilation and calculation procedures– Data editing– Conversion factors– Statistical calculations

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Inventory planning

8. Reporting the results, maintenance and storage of records– Number and distribution of copies– Storage and retrieval of data– Plans for updating inventory

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Example: Ontario Forest Resource Inventory (FRI)

• Originally designed in 1946 to locate merchantable timber species for supplying mills

• A large-scale survey that would allow general characterization of the forest in terms of species, forest conditions and regeneration

• Based on aerial photo interpretation, as well as some field surveys

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FRI Production

First Year• Acquire aerial

photography, taken at scales of 1:20,000 for northern Ontario and 1:10,000 for southern Ontario during summer conditions when trees are in full bloom

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FRI Production

• Second Year– Photo interpreters determine sample plots

and coordinate the collection of field data– Field data serve to calibrate the

interpretation of forest conditions depicted on the aerial photographs

– Attributes interpreted includes species composition, stand age, stand height, stocking and Forest Ecosystem Classification (FEC) site types

– Site class, an indicator of stand growth and productivity, is derived from the relationship between age and height

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• Third Year– Transfer of boundaries and attribute data from

the aerial photographs onto FRI maps– Automation, semi-automation involved

FRI Production

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• For management purposes, Ontario’s Crown forests are divided into 50 management units (as of April 2002). Forest Resource Inventories are required on each management unit about every 20 years. They must be updated at the start of each new forest management plan (every five years) to reflect all changes to the forest

• Changes includes: – depletions due to harvest or natural reductions,

such as those caused by wildfire, insects, disease, and blowdowns

– Accruals can also take place as a result of forest renewal and tending activities for both assisted and naturally regenerated areas

FRI Planning Schedules

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Forest Inventories - Recording Field Data

• Make them neat, concise, and accurate.

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Timber Inventory as a Sampling Process

• The conduct of inventory is a sampling process, except for those circumstance in which a complete tree tally is justified

• Involves in developing an efficient sampling scheme: – sample size– plot size & shape– sampling design (systematic, simple

random, stratified random, etc.

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Timber Inventory as a Sampling Process

• Regardless of inventory objectives, the method of selecting samples for measurement is based on sampling probability – Probability proportional to frequency– Probability proportional to size or point sampling– Probability proportional to prediction (3P)