The 2002-03 Chicago Wilderness Woods Audit:
Over two summers, 140 of us collected detailed vegetation data in 242 randomly-located plots in the wooded lands of eight Chicago Wilderness counties.
We identified wildflowers and grasses, counted shrub and sapling stems, and measured all of the trees within a circle 25 meters across. The result is a comprehensive assessment of the current condition of our upland forests, woodlands, and savannas.
What is the quality of our woods? One way to answer this is to look at the Floristic Quality Index (FQI) within the ¼ m2 quadrats we used to quantify the herbaceous plants and seedlings. The FQI combines a measure of the fidelity of each species to high quality habitat (its coefficient of conservatism, or its C-value) and the number of species in the quadrat. When we graded each of the 242 plots according to its FQI, we found that most of our woods are in poor or fair shape, with few good or excellent quality plots.
When we include other factors in our quality measure, such as prevalence of invasives and degree of oak reproduction, the numbers change a bit, but the overall story is the same: most of our woods need help.
Our study found that the bur oak (Quercus macrocarpa) woods are in the worst shape, followed by white oak (Q. alba) woods. Red oak (Q. rubra) woods are doing slightly better, and black oak (Q. velutina) woods are doing the best of these native oak woodlands.
We also found that trees such as black cherry (Prunus serotina) and sugar maple (Acer saccharum) are acting as invasives in our oak woods. We found many more young cherries and maples in the woods than we found young oaks, suggesting that the oaks are not reproducing sufficiently to sustain the native oak ecosystems.
One of our worst invaders is buckthorn (Rhamnus cathartica), which shades out native wildflowers and oak seedlings. Our study found a total of 18,763,866 sapling-size stems of buckthorn in the woods represented by this study. This means 558 stems per acre, not including all of the sprigs under one meter tall.
For more detail, see the Summer 2004 Chicago Wilderness Journal article that describes the study and its results. Some of the numbers in the article differ slightly from those given here, due to updated data and analysis since its publication. The conclusions remain unchanged.
What can we do? Our woods need our help. There are thousands of people in the region who are helping to remove invasive species like buckthorn, as well as planting native wildflowers and conducting other ecological management. With more and more of this good work, we will return our precious oak woods to their thriving, healthy selves. To help, check out the volunteer stewardship group nearest you.
Chicago Wilderness is using the results of the Woods Audit to garner increased funding for woodland restoration, so we can buy more loppers, more native seed, and more staff time for intensive restoration work. If you tell your public officials that you care about restoring our oak woods, they will be more likely to allocate increased funds toward this great work.