Spring 2006

INDIANA'S CHANGING FORESTS

Many of Indiana’s forests are maturing. This is a wonderfully mixed blessing. Galleries of large trees help kindle a sense of wilderness as we hike though our cathedral-like forests and parks. We are transported back to a historic time, when forests were untouched by saws; when deer, bear, cougar and wolves roamed the landscape; and when people lived off the bounty of the forest. Within the hushed forest quiet and deep shade, we can find our peace and spirituality with the outside world, where the balance of nature prevails.

Yet as our forests mature, they enter a time of transition, changing in ways that could diminish their value as habitat and home to many species. It is a slow change--almost imperceptible--that will ripple though our wildlife communities. But these ripples won't dissipate; instead they accumulate to the point that we cannot help but notice.

The very composition of our forest is changing in dramatic ways. The next time you hike though a state park or forest, or even a nature preserve, look at the trees above you. Chances are you'll see lots of white and red oaks, various types of hickory trees, maple, beech, and tulip poplar. Then take a look at the forest floor and try and find those same species as seedlings. It should be easy to find them all. But now look at the saplings and smaller "pole-sized" trees. The vast majority will be maple and beech. Oaks and hickory will be virtually missing. Once the mature trees are gone, either though natural death or through harvest, they will be replaced by a simplified forest of mainly beech and maple. Not that there is anything wrong with these species. It's just that oak, hickory and other slow-growing mast producing species have so much more to offer relative to conserving biodiversity.

The factors that are driving this shift are complex and intertwined. Oak-hickory forest is clearly transitional, but was originally sustained on our landscape by disturbances such as fire and blowdowns that removed or weakened canopy trees so that young oaks and hickories received the abundant sunlight they needed to thrive. Oak seedlings and saplings need lots of sunlight to outpace their competitors. In today's closed forests, these species are quickly overgrown by maple and beech seedlings which are more tolerant of dense shade. Typical forest harvesting practices today don't create the canopy openings required for oaks either. Often just the four or five best trees per acre are taken, creating light gaps that are too small for oaks to regenerate. Usually the maple saplings that were under the harvested tree fill the opening within a year or two, cutting off the sunlight for any oaks that may have been lingering.

Smokey the Bear hasn't helped us much on this issue either. Ground fire was originally a common occurrence in our forests. These fires, which oaks typically survive, usually kill the thinner barked fast growing species. This obviously gave oaks and other fire-resistant species an edge. But in today's forests, wildfire is a rarity that is quickly suppressed. And forest managers tend to dislike fire, because it can damage the base of high-value trees, diminishing their market value.

Many of Indiana’s forests have too many deer, and those deer love to eat oak seedlings and saplings. They don't seem to damage maple, tulip or beech nearly as much. In many forests, especially in areas where there is little or no deer hunting, few trees that deer like to eat are spared. At the herd densities we typically see across the state, deer selectively prune back seedlings that they find palatable.

Oaks are the base of the food chain for a complex web of animals including birds, mammals and insects. Acorns are the most important wildlife food in the deciduous forests of North America providing an essential and energy rich food available during the winter period. In addition, numerous birds and mammals depend on cavities for nesting and winter survival. Twenty-eight bird species are known to be cavity nesters in the region. Oaks include some of the more common tree species that produce cavities. Seventeen species of oak are found within Indiana with various species found across all forested habitats and regions of the state.

Oak forests support higher diversities of both plants and animals than do other forest types according to ornithologist Amanda Rodewald and forest ecologist Marc Abrams in their 2002 study, Floristics and avian community structure: Implications for regional changes in eastern forest composition. In a separate review of scientific studies by Amanda Rodewald in 2003 entitled, Decline of Oak Forests and implications for Forest Wildlife Conservation, she noted that 90 kinds of vertebrate animals are known to use acorns. Comparatively fewer animals heavily consume maple seeds.

There are many goals associated with forest management, but above them all should be the health of the system you are managing. Because some pre-settlement conditions such as wildfire are nearly gone from the landscape active forest management on public and private land is integral to maintaining diverse forest systems. Majestic old growth forests are awe inspiring and they represent a significant and important portion of the natural forest community. But if the entire forest were managed for those attributes, many of Indiana's most interesting species would greatly diminish. Oak-hickory forest itself is transitional, and will eventually give way to beech-maple forest as the decades pass. This process, accelerated by disproportionate harvest of oak trees, is well underway across much of Indiana. Successfully conserving all forest species will require some type of disturbance which re-sets forest succession and conserves oak-hickory or mixed oak forests.

Reversing this trend will take time, but the great news is that we have more than enough. We know how to re-introduce fire into the forest. We understand how to create light gaps. We know how to reduce the deer herd. On some lands in Indiana, forest managers are actively addressing these issues to lay the groundwork for creating the next generation of oak forest. As a society we would be remiss if we allowed the oak forests to slip though our fingers, simply because it happened so slowly that few people noticed.

In short, we need to recognize that there are tradeoffs to forest management as well as forest preservation. Some species will benefit from one and not the other, therefore it is important to plan ahead to get a good balance of habitats. Unless forests are well managed, a large proportion of species that we take for granted today will decline over the coming decades.

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