Predictive Open-grown Crown Width Equations for Three Oak Species Planted in a Southern Urban Locale

Models that predict ecosystem services in urban areas are useful tools to urban forest managers. Predictive open-grown crown width equations were developed for three oak species common in urban forests in the southern United States. Tree crown form is an important component of these equations; however, there are few predictive equations available for urban, open-grown trees. The species used were Quercus lyrata Walt. (overcup oak), Quercus nuttallii Palmer (Nuttall oak), and Quercus phellos L. (willow oak). The study authors believe that these are the first predictive open-grown crown width equations developed for these species in the southern U.S. Diameter at breast height (DBH) (independent variable), DBH2 (independent variable), and average crown width (dependent variable) data were used to create the predictive crown width equations and yielded R2 values of 0.96, 0.94, and 0.91 for overcup, Nuttall, and willow oaks, respectively. These equations can aid urban landscape and utility planners by providing a means to predict crown dimensions at varying trunk diameters. Field time could also be minimized by reducing the need to measure crown width and with time, these equations could be used to validate species specific equations (e.g., leaf biomass) for these and other southern urban-planted tree species.

Barking up the wrong tree: climbing performance of rat snakes and its implications for depredation of avian nests

Nest depredation is the leading cause of nest failure in Neotropical–Nearctic migratory birds, which are of interest because of their declining populations. In a recent study in a bottomland hardwood forest, Acadian Flycatchers (Empidonax virescens) experienced higher nest success in Nuttall oak (Quercus nuttallii), a tree species with relatively smooth bark at maturity. To determine if variation in bark-surface irregularities may influence the ability of a predator species to access the contents of avian nests, we examined the climbing abilities of rat snakes (Elaphe obsoleta) on trees having three different bark types. None of the subjects was able to ascend large Nuttall oaks in the absence of vines; with vines present, subjects still required more time to climb Nuttall oaks than to climb other species. A few of the subjects successfully climbed smaller Nuttall oaks lacking vines, but ascent time was longer and climbing behavior was modified from that observed in the other trials. Our results indicate that the likelihood of nest predation by rat snakes decreases in this forest when birds nest in trees with smooth bark and without vines. Investigators need to consider differences among nest substrates that are important to both the prey and the predator.

Survival and Growth of Nuttall Oak Seedlings Following Selection Cutting—28-Year Remeasurement

A Nuttall oak (Quercus nuttallii Palmer) seedling stand that averaged 138,000 trees/ac 1 year after establishment from the 1957 seed crop was reduced to 708 trees/ac after 28 years where seedling release consisted of a one-time selection cut. None of the dominant/codominant trees atage 28 were oak, and only 20% of the plots had oaks of intermediate crown class. The regenerated stand will apparently become ash-sugarberry to replace the original stand that was two-thirds oak. South. J. Appl. For. 13(1):43-46.

Development of Nuttall Oak Following Release in a Sapling-Sized Stand

Release treatments applied to 11-year-old direct-seeded Nuttall oaks (Quercus nuttallii Palmer) did not significantly increase the number of free-to-grow oaks at age 17 compared to oaks that did not receive release treatments. Treatments consisted of cutting or deadening other species that were as tall as, or 1-1/3 or 1-2/3 times taller than, the average 15-ft-tall, free-to-grow oaks. South. J. Appl. For. 12(1):46-49.

Oak Seeding—It Can Work

Nearly 20,000 acorns of Nuttall oak (Quercus nuttallii Palmer) were direct-seeded in Sharkey clay soil in the Mississippi Delta. Acorns sown 1 inch deep in January gave significantly better germination, 55 percent of total sown, than did eight other combinations of three storage treatments with three sowing depths. Rodents destroyed most acorns sown in the understory and in forest openings <1/10-acre but hardly bothered acorns sown in 350-foot square forest openings cleared to ground level. After 10 years in the larger areas, 75 percent of the seedspots, spaced at 5- x 10-feet and sown with four acorns each, were stocked with one or more living trees. About one-third of the oaks were in a free-to-grow position. Average height and d.b.h. of the largest oaks, one from each of 162 treatment rows, were 17.8 feet and 1.8 inches. Five-foot wide strips were mowed between the 10-foot spacing. After 10 years, there were 14,142 total trees per unmowed acre.