Principle – Yield and Quality of Forest Goods are Sustainable

Criterion- Forest management provides for sustainability of goods and services.

Indicator – Mean annual increment for forest type and age class.

Box B: Definition:

Mean Annual Increment (MAI) is the average growth of the stand up to the age in question. It is calculated by dividing yield at that age by the age itself.

Growth in a regulated forest can be measured by the product of the forest average times the mean annual increment of an average stand over its life (MAI+A). Since harvest is equal to MAI forest acreage here, harvest equals growth in a regulated forest

According to CCFM source, the MAI is the average net annual increase in the yield (expressed in terms of volume per unit area) of living trees to a given age, and is calculated by dividing the yield of a stand of trees by its mean age.

Box D: Applicability to Different Landowners. Explain any differences:

It is applicable to all land ownership for the land that is being used for commercial wood production.

Box E: Overlap:

CIFOR 3.2.3

CCFM 5.1.1

Notes: NA; Structure, function and composition are ecological parameters

Box I: Underlying Concepts:

According to CCFM source, the MAI is dependent on a number of factors, including climate and elevation, soil conditions and forest management practices. MAI is a measure of the net biomass production of the forest and can be used to indicate its productivity. However, production loss due to mortality, insects and disease is not included; therefore, total growth before losses generally is considerably larger than net growth.

A measure of frequency of biota occurrence within selected indicator species, in combination with a measure of MAI by forest type and age class, provides a reliable measure of forest ecosystem condition.

Box J: Relevance to Sustainable/Unsustainable Management:

The indicator is only relevant to areas included in wood production.

A forested ecosystem that is healthy, vital and self-perpetuating is considered to be functioning normally. The sustainable development of an ecosystem implies normal functioning over the long term.

Box K: Measurement Methods:

The ideal source of information for this indicator would be tree measurements taken every 5-10 years on permanent sample plots located in a variety of forest conditions (CCFM Source).

Davis and Johnson, 1987, described the standard method for measuring MAI.

Box L: Data Required:

This is an indicator that has generally available data for forested lands in the World. The ideal source of information for this indicator would be tree measurements taken every 5-10 years on permanent sample plots located in a variety of forest conditions (CCFM Source). The main parameters that have being measured are DBH, Tree Height and Stem Height. These measures will reveal changes over time in forest ecosystem productivity, health and vitality.

Box M: Data Used for the North American Test:

Lyn Morelan provided annual net growth by age class and area by forest type and age class a list of BNF tree species, from the Boise National Forest. Data came from USDA-FS-BOISE NF. 1985. Inventory, Forest as a whole (no constraint).

We divided the annual net growth by the area within each forest type and age class so that we got the main annual increment for each age class and type of forest. A summary of these data is presented in a table from the USFS-BNF in Box N. The average for all total classes and all total types of forests is 98.5 board feet per acre per year, which is lower than those averages in forests managed by Idaho Department of Lands.

We also used data for the annual net volume change per acre in Southwestern Idaho and Payette Lakes Supervisory Areas, from Idaho Department of Lands, whose average from 1974 to 1996 for all timber types is 145 and 153 board feet per acre per year, respectively.

Source: USDA-FS-BOISE NF. 1985. Inventory. Forest as a whole (no constraint). pp. 4.

Box O: Assessing the Practicality:

This indicator can be tracked over time and does not require special arrangements since it is being done by all agencies.

Box P: Assessing the Information Value:

Many management decisions are or can be influenced by the MAI, specially decisions relative to wood production, which will affect sustainability.

Box Q: Overall assessment:

Accepted with the following weaknesses:

• It only tells us about one resource value, which is timber.
• It considers contributions from suitable timber production acres at stand level.

Box R: Did you rewrite or revise to a new indicator. If so what?

No

• CIFOR Source. Forest management issues sent from Indonesia to North American Team by e-mail on June, 23^rd 1998. 58p.
• Canadian Council of Forest Ministers. 1997. Criteria and indicators of sustainable forest management in Canada. Ottawa ON. Technical Report. Cat. Fo75-3/6-1997E. ISBN 0-662-25623-9. pp39-41. 138p.
• Davis, L.S. and K.N. Johnson 1987. Forest management. 3e. McGraw-Hill. 790 p. (pp 540-543 and 51).
• Koski, W. 1998. Idaho Department of Lands, Continuous Forest Inventory Report, Payette Lakes Supervisory Area, 1996 Remeasurement. Idaho Department of lands, Boise, Idaho
• Koski, W. 1998. Idaho Department of Lands, Continuous Forest Inventory Report, Southwestern Supervisory Area, 1996 Remeasurement. Idaho Department of Lands, Boise, Idaho
• USDA-FS-BOISE NF. 1983. Boise National Forest Inventory. Unpublished document with more than 500 pages.
• USFS-Intermountain Region-BNF. Land and resource management plan for the Boise National Forest. pp II-34 to II-35.