Incredible Gambel Oak

Gambel Oak woodlands protect our watershed by stabilizing the soil and support a plethora of life not readily apparent to most passersby. It begins beneath our feet; a world of soil, roots, microbes, invertebrates, and fungi that we can never fully experience. I know almost nothing about subterranean ecosystems but they are intriguing support systems for the landscapes we see around us. Just above the soil, the decaying leaf litter shelters a wide variety of creatures including spiders, slugs, woodlice (pillbugs), ticks, and millipedes. Ecological surveys of Gambel Oak woodlands beginning in the 1940s demonstrated that many more invertebrates live in oak leaf litter than in surrounding grassland habitats. They are excellent foraging areas for insectivorous birds and other creatures that like dining on arthropods, seeds, and/or acorns. 

As we move off the ground and up the oak trees, we find lichens, beetle larvae, and other small creatures hidden within the gnarled bark. The branch network is dense and provides protection for singing birds or rock squirrel sentinels looking out for danger. It is easy for a junco to hide amongst the branches but not so easy for a Cooper’s hawk to dive in after them. Some birds nest on the ground or tucked into the thicket. 

Smaller branches, twigs, acorns, and shoots provide good forage for various mammals, although Gambel Oak contains tannic acid which is toxic in large quantities. Oak stems are also home to a fungus that causes stem galls - puffy, blister-like growths. Leaves are eaten by various insects like leafrollers and cankerworms, which in turn are delectable to birds. Many different gall wasps lay their eggs in leaves, causing small bumps or round balls to form. These are leaf galls and are generally harmless to the plant while providing shelter for the tiny larvae. Other parasitoid wasps lay their own eggs on the gall wasp larvae, if they can find them, for their own larvae to devour. Most gall wasp species are partly parthenogenic, meaning that some generations are entirely female and reproduce asexually.

This article is only a short preview of the incredible life found in Gambel Oak woodlands. I hope it makes you curious about the organisms we can step outside to observe and discover.

By Maria Goller