Fall is the time of harvest here in the Midwest. Golden stacks of hay bales, farmer’s markets teeming with end-of-season produce, and above all, apples. But step away from the orchard and into an oak woodland and you’ll find a different kind of autumn apple: an oak apple gall. What looks like a small, lime-green, spotted apple dangling from an oak leaf is not a fruit at all, but rather a secret abode for a tiny wasp.
There are more than 50 species of oak apple gall wasps in North America. Each one creates a unique fruit-like structure that protects and feeds its eggs and larvae as they develop. Lately, I’ve been finding many dried, spent brown husks created by the larger empty oak apple wasp (Amphibolips quercusinanis) around the Lake County Forest Preserves in northern Illinois.
Fall is my favorite season. I know it’s here on the first day I walk outside into the sort of air so crisp it makes your nose run instantly, somehow in a good way. Sunset shifts sooner. You opt for a sweater instead of a t-shirt and everything pumpkin-flavored becomes tastier than you remember. Best of all, the crowns of oaks, hickories, maples, and more across the Lake County Forest Preserves in Illinois change into their vibrant fall fashions.
My family went on a bike ride last weekend at Ray Lake Forest Preserve. All afternoon, rain sputtered on and off as the clouds played tag with the sun. After climbing up a steep hill, the sky darkened again and we sought refuge under a canopy of large oak trees. One of my sons yelped,”Ouch! That raindrop hurt!” We quickly realized it wasn’t a raindrop, but a storm of acorns jiggled loose by the wind, plopping down on us. The trail became littered with acorns, and the kids began grabbing them. Upon inspection, the boys noticed tiny round holes in many of the acorns—evidence that these nuts were homes to acorn weevils (Curculio spp).
The wooded habitats along the Des Plaines River in southern Lake County, Illinois are changing. Last winter, the Lake County Forest Preserves completed 194 acres of canopy and understory thinning in woodland communities at MacArthur Woods and Grainger Woods Forest Preserves. This winter, woodland habitat restoration has begun at Captain Daniel Wright Woods and Ryerson Conservation Area, in addition to continuing at MacArthur Woods.
The restoration and species monitoring that will continue within these natural areas for the next 20 years will help ensure the sustainability of oak woodlands and the wildlife they support for many generations to come.
Winter visitors to these preserves, or vehicular passersby, will notice the use of heavy equipment, burning piles of brush, and an already visible difference in the openness of the woodland landscape. A number of canopy trees are being removed to increase the amount of sunlight reaching the ground. Visit these areas again when the leaves return, and early results of the Woodland Habitat Restoration Project will be obvious. Continue reading →
Even though Illinois recently received a break from this summer’s heat and drought, the precipitation deficit that remains statewide has kicked off autumn with atypical natural events. Thus far, the year 2012 has been the fourth driest on Illinois record. However, it has been raining acorns and fall colors have been peeking through the greenery since late August—three weeks earlier than usual. This fast-forward to fall is a tree’s way of protecting itself when water is in short supply. The vibrant color displays of autumn, which seem so lively, are actually a sign that a tree is entering dormancy.
These flashes of fall colors are a result of changes in pigments. The dominant green pigment in leaves is chlorophyll. The leaves in a tree are like little factories, mixing together a recipe of specific ingredients (sunlight, carbon dioxide and water) to make food for the tree’s growth. Chlorophyll acts as the “chef” in this process, called photosynthesis; its presence is necessary in bringing everything together.
Typically, autumn’s cool nights and shortening days trigger photosynthesis to slow down. The scarcity of one key ingredient, water, is triggering this earlier-than-average dormancy. As the work of the leaves comes to an end for the year, chlorophyll breaks down and reveals yellow and orange pigments that have hidden behind its green cloak all summer. Leaves that contain the pigments xanthophyll and carotene—as do hickories, cottonwoods, elms and some maples—will change to vivid shades of yellow and orange as the green fades. Continue reading →