Oak Methods

A columnar oak tree covered in branches from underneath

Live Oaks

The Birds & Blooms team surveyed living oaks, as well as dead trees of any species, within the woodland of Dorris Ranch. Measuring the response to restoration efforts through tree characteristics helps to evaluate the condition of threatened oak habitats.

We identified Oregon White Oaks by their bark, growth pattern, and leaves. All oaks over 14 inches at diameter breast height (DBH) were geolocated for mapping, assigned a unique code, then measured. Each live oak was measured for crown characteristics of width, density, live crown ratio, percent crown contact, and crown shape. The number of boles (tree trunks) were measured by how many were  present at breast height. Epicormic sprouts (new growths) signaled a positive response to thinning, and were counted below the first split in the trunk.

The shape of the Oregon white oak can also indicate the health of the tree. Oregon white oaks were shade intolerant and oaks naturally grow, when not hindered by competition, in a large mushroom shape. Oaks that were more vertical and columnar suggested stress from nearby competition, such as Douglas-firs, that can shadow the crown of oaks, and thus inhibit the formation of a mushroom shape.

A team measuring the DBH of a white oak

Dead Oaks (Snags)

Many of our target native species were cavity-nesting birds. Recorded information about snags (dead trees) and cavities helped us determine the health of the avian habitat at Dorris Ranch. Snags were identified by species, decay class and DBH. Canopy characteristics were not measured as snags do not produce a live canopy. Our team used bark and branching characteristics to identify snag species. Only snags measured over 11 inches DBH were counted.

Decay class was recorded in five classes, with 1 being the least decayed (recently dead trees with the top and bark intact and with possible foliage present) and 5 being the most (heavily decayed with no branches or bark and all foliage is gone).