The Nature of Oaks by Douglas W. Tallamy

Abstract

As a restoration ecologist and environmental historian with a long-time interest in the use of acorns and management of oaks, I approach new books on oaks with a somewhat skeptical eye. Douglas Tallamy’s latest book “The Nature of Oaks” was a delightful surprise. This is a book anyone involved in restoration or management of a property with oaks will find of interest. Even if you don’t work with oaks, the complex ecosystems in oak leaf litter, on branches and leaves, and in cracks in bark will offer new insights into the complex interrelationships with which you might be dealing and should consider. The book follows the oak year, month by month, with insight into the often unseen insects, worms, nematodes, and fungi found in and under oak trees. These can be found in surprising numbers, up to 100,000 springtails (collembolas) per square meter. Tallamy also reveals how important the understory is, something I did not even imagine. Most of the caterpillars found on oaks fall to the ground to pupate or spin a cocoon in the litter. If the ground is mowed, bare or compacted, the insects will not survive. This will mean fewer caterpillars for the many birds that rely on them to feed their fledglings. Nesting birds may require tens of thousands of caterpillars for a successful nesting season (Tallamy 2019). Excellent color photographs bring the oak insect world to life. The complex oak litter ecosystem helps reduce the spread of invasive Microstegium vimineum (Japanese stiltgrass) and several invasive worms that are killing off the native worms. Collembolas, for example, graze on and reduce the impact of pathogenic Fusarium fungi (Klironomos and Bainbridge, 1995). Tallamy discusses the many environmental benefits oaks offer, including carbon sequestration (in tree roots as well as trunks and branches). These lovely trees can lock up carbon for hundreds or thousands of years. The mycorrhizal fungi growing on oak roots also sequester carbon as glomalin (Hossain 2021). Oaks aid in water retention and reduce flooding. They feed myriad species of birds, animals, and smaller creatures down to the size of soil mites. He offers a short guide to many of the 91 oak species in North America and bemoans their loss. Almost a third are considered at risk. His research group has exposed the problems caused by using non-native species in landscaping and the invasion of unwanted species. Working with his students, he matched four invaded to four native hedgerows. The invaded hedgerow still had some native species, but caterpillar biomass had dropped 96%. Tallamy gives advice on selecting the best oak species for your area and discusses the challenges and options for planting and caring for oaks. Tallamy is a professor in the Department of Entomology and Wildlife Ecology at the University of Delaware. His information is most detailed on the eastern oaks he knows best, but he does discuss some of the western oaks. The only thing missing is the story of the management and importance of oaks and acorns for hundreds of tribes and hundreds of thousands of people prior to the European invasion (Bainbridge 1987, 2001).