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 to a specified age. For example, a 20-year old tree that has a diameter at breast height (dbh) of 10.0 inches has an MAI of 0.5 inches/year. MAI is calculated as where Y(t) = yield at time t. Because the typical growth patterns of most trees is sigmoidal, the MAI starts out small, increases to a maximum value as the tree matures, then declines slowly over the remainder of the tree's life. Throughout this, the MAI always remains positive. MAI differs from periodic annual increment (PAI) because the PAI is simply the growth for one specific year or any other specified length of time.
The point where the MAI and PAI meet is typically referred to as the biological rotation age. This is the age at which the tree or stand would be harvested if the management objective is to maximize long-term yield. The proof of this definition is shown by differentiating MAI(t) with respect to t, and is shown by Husch, Miller, and Beers
Famous quotes containing the word annual:
“No annual training or muster of soldiery, no celebration with its scarfs and banners, could import into the town a hundredth part of the annual splendor of our October. We have only to set the trees, or let them stand, and Nature will find the colored drapery,—flags of all her nations, some of whose private signals hardly the botanist can read,—while we walk under the triumphal arches of the elms.”
—Henry David Thoreau (1817–1862)