How old (or young) are Indiana’s trees?

There are very few, if any, isolated areas of Indiana forestland where trees have never been cut. Most of these areas are recognized as small treasures and preserved in state parks, nature preserves, and the Pioneer Mothers Memorial Forest within Hoosier National Forest. Most trees we see today have been growing since 1900. There were as few as 1.5 million acres of forest in Indiana at that time, compared with 4.5 million acres in 1998.

Figure 12 - Indiana Timberland age by Forest Type, 1998.Like all living organisms trees begin life, grow and die. Some tree species are relatively short-lived. For example, aspen and cottonwood have an average life span of 60 to 90 years. Most hardwood trees found in Indiana grow for 100 to 150 years. Some trees, such as white oak, can grow and flourish well beyond 150 years.

The state’s timberland age is displayed three different ways: by forest type (trees that are normally associated with one another), by timberland owner, and by survey unit. Trees selected to determine age are those that can freely grow without competition for sunlight or soil.

In general, the oldest trees in Indiana are oaks and hickories. Figure 12 shows that most of the state’s trees in the oak-hickory forest type are more than 60 years old. Indiana’s oldest measured trees (156, 151 and 140 years old) are black oaks and chestnut oaks. In contrast, all measured trees in the aspen-birch forest type are less than 60 years old. It is interesting to note that pines are mostly between 30 and 60 years old.

These trees were planted from the 1930s to the 1960s in an effort to stabilize soil depleted by poor farming practices. Indiana’s soil is in better condition now than it has been in decades and supports native tree species such as oak, ash, and black cherry. In areas originally planted with pines, hardwood trees are again beginning to take root and grow. This is a true success story!

Picture of forested valley.

Figure 13-Timberland age by percent of survey unit.In general, each of the four survey units has about the same proportion of age groups (Figure 13). The Northern Unit contains a variety of ages that closely resembles the entire state. The Knobs Unit tends to have slightly older trees, probably due to the larger amount of public timberland compared with other units. Each unit has some trees older than 100 years; however, across all units, the largest proprtion of trees is between 31 and 60 years old. The next largest proportion of trees is 61 to 80 years old, except in the Upland Flats Unit. Figure 14 illustrates the area in acres that each age group occupies within the survey units.

Private individuals and corporations own more of Indiana’s timberland than other entities do. When comparing the ages of privately owned timberland (Figure 15) to those statewide (Figure 13), the two are very close in distribution. Most privately owned trees are also between 31 and 60 years old; however, there is a wide variety of tree ages on private land.

Figure 14 - Timberland Age by Acres in Survey Unit, 1998.Public timberland, owned either by the state, counties, or the federal government (national forest and other federal land) is generally comprised of land no one wanted. Many of these lands were burdened with high taxes and eroded soil that was no longer suitable for farming.

Much of the land that became the Hoosier National Forest was already reverting to forestland when the federal government began purchasing it in the mid-1930s. The government continues to acquire additional land for the Hoosier National Forest, to a limited degree, to provide recreational access, and to protect and enhance special natural resource features. Very few national forest trees are over 100 years old. Most timber is now between 31 and 80 years old— a testament to the forgiving nature of Hoosier land. The area has recovered from over-used, eroded soils, and now produces fine forest communities.

Figure 15 - Indiana Timnberland Age by Owner, 1998.Other federal timberland in Indiana consists of federal wildlife refuges and military properties. On wildlife refuge property, trees are actively managed to achieve desired wildlife habitat conditions. Where possible on military lands, trees are managed for multiple resource benefits. Over 50 percent of other federal timberland is less than 60 years old (Figure 15). Overall, federal timberlands have a good distribution of tree ages despite this relatively young age.

There are more old trees on state-owned timberland than on timberland owned by other groups (Figure 15). State-owned land also provides the most evenly distributed or balanced age groups of trees. Other than a slight amount of county and municipal timberland included in this owner group, state-owned timberland areas are primarily managed as state forests and state wildlife management areas.

Picture of forest undergrowth.Does age matter? Yes. A range of tree ages is good for the health of Indiana’s forests. Insects and disease, sometimes both, often attack either a certain age or type of trees. By maintaining a variety of ages and types, timberland is unlikely to be completely devastated by any one organism. This speaks well for the future of our forests.

In addition, different ages of trees provide various habitats for animals. Young forests teem with insects and many species of birds due to the variety of vegetation in the area (such as wild berries and sumac). Older, mature forests provide a different mix of habitat required by other animals.

Picture of forester by old growth tree.Picture of forest trail.

Different ages and sizes of trees provide a variety of forest products, from firewood and pallets (young and small trees) to fine hardwood veneer and lumber for furniture and cabinets (large and old trees). It is also important to maintain a good distribution of tree ages to provide products and habitat now and in the future.

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