Mean Annual Increment

The days have ended when the forest may be viewed only as trees and trees viewed only as timber. The soil and the water, the grasses and the shrubs, the fish and the wildlife, and the beauty of the forest must become integral parts of the resource manager’s thinking and actions.
– Hubert Humphrey 1976 cited in This Doc

Mean Annual Increment (MAI)
Forest Investment Associates

The average annual increase in volume of individual trees or stands up to the specified point in time. The MAI changes with different growth phases in a tree’s life, being highest in the middle years and then slowly decreasing with age. The point at which the MAI peaks is commonly used to identify the biological maturity of the stand and its readiness for harvesting.

Mean annual increment
Wikipedia “The mean annual increment (MAI) or mean annual growth refers to the average growth per year a tree or stand of trees has exhibited/experienced up to a specified age. For example, a 20-year-old tree that has a stem volume of 0.2 m3 has an MAI of 0.01 m3/year…”

Stand measurements
In Tree and Forest Measurement published by Farm Forest Line (Australia)

Canada’s Timber Supply: Current Status and Future Prospects under a Changing Climate
Dan McKenney et al., 2016. NRC. “Our objectives here are to: 1) provide a brief overview of Canada’s forest resources and summarize recent trends in the timber supply situation, and 2) present preliminary findings from a modelling exercise on the effect of climate change in the coming century on timber supply. Section 2 provides an overview of the components affecting timber supply in Canada, including forest industry, inventory, products, and international competition; it concludes with a brief review of studies that have examined the projected effects of climate change on the forestry sector in Canada/North America. Section 3 provides early results of new computer-based modelling which integrates data on current forest condition and mill attributes with projected forest yields and fire regimes to estimate timber supply through the end of the current century. The results must be viewed with caution because of their preliminary nature, but we hope they also provide motivation for more efforts on the subject.”

DNR Wisconsin

Land Capability and Site Index Curves for Nova Scotia Hardwoods
Tim McGrath, NSDNR 2011 “Site Index (SI) curves and Land Capability (LC) ratings are important tools used to estimate productivity of forest stands in Nova Scotia. Land Capability ratings are used to define sustainable levels of harvest and appropriate management prescriptions (among other uses). In 1987 (NSDLF), SI curves
were produced for Nova Scotia hardwoods based on stem analysis data. Preliminary combined SI and LC curves were then produced for the Forestry Field Handbook (NSDNR, 1993). The LC portion of these curves was based on an earlier version of the Hardwood Growth and Yield Model (HWGNY) whose methods are described in NSDLF (1990). An updated version of the HWGNY was published in 2006 (O’Keefe and McGrath). This model was used to create updated combined SI and LC curves for this report. Separate curves were produced for Intolerant Hardwoods, Tolerant Hardwoods and Aspens.”

Ten Year Periodic Annual Increment For Nova Scotia Permanent Forest Inventory Plots 1980-85 to 1990-95
NSDNR 2000

Revised Normal Yield Tables for Nova Scotia Softwoods
NS lands and Forests, 1990

Forestry Field Handbook
L&F This handbook includes site specific softwood and hardwood silviculture keys together with graphs and tables needed to estimate present and future stand characteristics. Each page of the book can be viewed (~ 80 k) — see Table of Contents or download the following compressed file for later viewing.
The growth projections and keys were developed by the Department of Natural Resources from research data and private and government experience. They are applicable to a wide variety of forest conditions, since decisions regarding the choice of silviculture treatments are based on specific site and stand characteristics. Explanatory notes providing further information about each of the silvicultural treatments can be obtained by request.
Forestry Field Handbook Table of Contents, e.g.:
Factors for Calculating Softwood Merchantable Volume. Pg 30
Factors for Calculating Hardwood Merchantable Volume. Pg 31
Factors for Calculating Softwood Sawlog Volume. Pg 32
Factors for Calculating Hardwood Sawlog Volume. Pg 33

2009 Medway District Annual Report Public Summary
Indicators relating to the ten principles of the FSC Maritimes Standard have been monitored and reported. The purpose of this report is to provide a summary of the benchmark indicators completed in 2009. There are several new initiatives that have been undertaken as a result of implementing the FSC Maritimes Standard in Medway District.

Healthy Forest Coalition
“In a letter to Atlantic Forestry Review Ed Bailey, former Director of Silviculture at DNR defends even-age management and in doing so sheds light on DNR assumptions regarding allowable cut and yield per acre. He advocates pre-commercial thinning (PCT) of young stands that are regenerated from clearcuts when they are ‘roughly 10 feet high. This treatment creates windfirm stands, greatly increases the proportion of desirable species and stems, and shortens the rotation by 20 years, contributing to the allowable cut effect (ACE). It also reduces losses to windthrow by allowing harvesting at a younger age and lower height. For example, at age 45 (i.e. 30 years after spacing), average PCT stands will have reached peak mean annual increment (maximum volume production), average eight inches in diameter and 40 cords per acre, with almost trees harvestable as studwood and sawlogs.’ In an editorial note David Lindsey questions Bailey’s focus on yields as opposed to outcomes that protect biodiversity, wildlife habitat, soils and water resources. (AFR January 2014, pp. 9-11)]

Calculation of Mean Annual increment by Forest Type and Reconciling With Expected Management Plan Yields Mean Annual Increment
Steven Spears 2000 . Fundy Model Forest

Optimal rotation age
Wikipedia “In forestry, the optimal rotation age is the growth period required to derive maximum value from a stand of timber. The calculation of this period is specific to each stand and to the economic and sustainability goals of the harvester.”

Periodic annual increment

Assessing Potential Sustainable Wood Yield
ROBERT F. POWERS In: Thi! Forests Handbook.. 2001. Julian Evans (Ed.) Vol 2. Applying Form Science for Sustainable Management Blackwell Sdena, Ud. Oxford, U.K.

Forest site productivity: a review of spatial and temporal variability in natural site conditions
ens Peter Skovsgaard* and Jerome K. Vanclay Forestry 2013 v 86: 305–315

Traditional Sustained Yield Management: Problems and alternatives
John L. Walker. 1990. In The Forestry Chronicle “Sustained yield has been a tenet of faith among foresters since forestry emerged as a profession. In some circles
it has been elevated to the level of other unassailable institutions such as motherhood, democracy and religious freedom. My purpose on this panel is to review some serious problems with the concept and offer an alternative.

Policy Background Paper Produced by the Royal Commission on Forest Resources Victoria, British Columbia August 1975

Erdle’s dream: Accord could increase protected areas by increasing intensive management
Editorial in AFR, Sep 2019

Allowable Cut in Forest Management
Jerome K Vanclay In: Tropical Forestry Handbook (Eds L Pancel & M Köhl), 2nd Edition, Springer (2014) “Allowable cut is a guide used to regulate timber harvests in both plantation and natural forests. The concept is long-established, but it remains loosely defined as “the volume, number of stems, or area cut over, either annually or periodically” (Ford Robertson 1971). Over the years, various formulae and algorithms have been proposed to assist with the calculation of the allowable cut, but until recently the underlying tenet has not been seriously challenged. However, in recent time, the concept has been criticised on both economic and ecologic grounds, and alternatives have been offered. The term ‘allowable cut’ is sometimes been used to denote the total quota allocated to log purchasers (e.g., Vanclay 1996a), but the present context is that of an evidence-based estimate of the harvest that can be sustained long-term, and not of a politically-convenient agreed harvest.

Forest Economics
G Cornelis van Kooten, lecture slides. Mathematics of Volume versus time, Timber yield versus time, Current Annual Increment, Mean Annual Increment; tMSY = Foresters’ Rule is to harvest at age that maximizes the mean annual increment, MAI; MSY rotation age occurs at the time when culmination of MAI takes place – where CAI intersects MAI

FAO: Guidelines for forest management planning


A Critique of Silviculture. Managing for Complexity –
Klaus J. Puettmann, K. David Coates, Christian Messier. Island Press, 2009