Summer 2010

Volume 19 No. 2

The Hardwood Ecosystem Experiment - Part 1

by Brian MacGowan

Forests appear to us to be static and unchanging over time; a visit to your woods today may not look much different than 10 or 20 years from now. In truth, though our forests undergo constant change. Orderly, unidirectional change in the composition and structure of an ecological community is called ecological succession. In most cases, succession is gradual and goes unnoticed in our fast-paced lifestyles. But succession is interrupted occasionally by disturbance.

Many disturbances including fires, tornados, insect outbreaks, and timber harvesting can be immediate and dramatic. Within our forests, these disturbances result in changes in plant species composition and structure that are important to Indiana’s forests and the wildlife that live in them. While much attention has been given to forest wildlife, the scope of disturbance can also affect what tree species will inhabit a site in the future. For example, oak species make up a large part (up to 80%) of the overstory in forests within Indiana and the Central Hardwoods Region. However, succession without disturbance has led to the understory has become increasingly dominated by shade-tolerant beech and sugar maple trees. This disparity has been attributed to fire suppression and the reduction/ absence of even-aged timber harvesting in recent history.

We harvest timber to make furniture, build houses, and much more. But it can also serve to mimic natural disturbance and create early successional communities upon which many species of wildlife depend. Given the trend in forest ownership patterns (60% of Indiana forest landowners own <9 acres), scientists do not believe that creating a balance of early successional habitat stages will be feasible on small private land ownerships. Research in other states tells us that early successional habitats are most beneficial to wildlife species when they occur in large blocks of forest cover (>1,000 acres) adjacent to older stands of hardwoods.

Thus, large tracts of public forests may offer the best opportunity to maintain early successional habitats. Disturbance will impact plants and animals in different ways. Some species will benefit while others will not. The challenge we face is that disturbance of some type is necessary to continually create early successional habitats, but late-successional habitats must also be provided. How do we achieve a balance of successional habitats in Indiana forests? The Hardwood Ecosystem Experiment is a long-term, scientifically rigorous study designed to provide land managers the answer to that and more.

What is the HEE?

The Hardwood Ecosystem Experiment (HEE), initiated May 2006, is a collaborative project among the Indiana Division of Forestry; scientists from Purdue University, Indiana State University, Ball State University, and Drake University (Iowa); and partners including the Indiana Division of Fish and Wildlife, The Nature Conservancy in Indiana, and the USDA Forest Service. The main goal of the HEE is to understand the ecological and social impacts of forest management on public and private lands.

Research efforts have focused on sites at Morgan-Monroe and Yellowwood State Forests where scientists are studying how even aged (10-acre clearcut and shelterwood) and uneven-aged (single tree and group selection) harvesting impacts plants and animals compared to control sites. Nine study areas ranging 900-1000 acres in size were randomly drawn from 11 possible areas. Each of the nine units was randomly assigned to a treatment, with 3 control units, 3 uneven-aged management units, and 3 even-aged management units.

From 2006 to 2008, researchers collected data prior to any harvesting activity. A variety of different species/communities were included in the study with special emphasis on threatened and endangered species. Researchers are studying forest dynamics, oak mast, bird communities, Cerulean warblers, wood boring and longhorn beetles, moths, small mammals, bats, salamanders, eastern box turtles, timber rattlesnakes, deer browsing, and perceptions and attitudes of people. During the fall of 2008 through winter of 2009, timber harvests were conducted on the six treatment units but not on the three control units.

Since 2009 and beyond, researchers will continue data collection on all of the units. The design and scale of the HEE is unique. By comparing data collected among control, even-aged, and uneven-aged units both before and after harvesting, researchers will begin to understand how harvesting impacts a wide suite of plants and animals. Part 2 of this story will feature some of the preliminary findings of the HEE and what that means for forest management. Visit   HEEForestStudy.org for more information. 

Brian MacGowan is an Extension Wildlife Specialist with Purdue University’s Department of Forestry and Natural Resources and studies box turtles and timber rattlesnakes on the Hardwood Ecosystem Experiment.