Data from the last two inventories of timberland in the Lake States, U
SA were used to determine the area, ownership, distance from roads, an
d changes in average stand age of existing and potential old forests i
n the region. Inventory dates, by state, were 1980 and 1993 for Michig
an, 1977 and 1990 for Minnesota, and 1968 and 1983 for Wisconsin. In t
his paper, timberland is considered forest land that is capable of gro
wing at least 1.4 cu m per ha per year of wood under natural condition
s and that is not reserved from harvesting. (Old forests are more than
120 years old, and potential old forests are between 80 and 120 years
old.) During the most recent inventory, 2% of the total area of timbe
rland was old forest and 14% was potential old forest. The maple-beech
-yellow birch (Acer-Fagus-Betula alleghaniensis) forest type accounted
for about 40% of both old forest and potential old forest. Private la
ndowners owned more than 70% of all old forest timberland in the previ
ous inventory and 64% in the most recent inventory. On average, old fo
rests and potential old forests were found significantly farther from
maintained roads than other timberland. As a result of increased stand
age, more than 200 thousand ha of potential old forest in the previou
s inventory were reclassified as old forest in the most recent invento
ry. Natural disturbances resulted in a decrease of almost 14 thousand
ha of old forest between inventory periods. Human-induced disturbances
accounted for most of the area of old forest lost between inventories
. Plant succession, natural stand aging, improved stocking levels, or
reclassification to timberland resulted in more than 1.2 million ha be
ing reclassified as potential old forest.