Frequency, severity, and detectability of internal trunk decay of street tree Quercus spp. in Tampa, Florida, U.S.

Abstract

Wood decay is a factor considered in all commonly accepted tree risk assessment methods; however, few studies have attempted to assess its presence in the urban forest or its predictability given visual cues and site factors. A random sampling of trees situated on hurricane evacuation routes was inventoried and assessed for risk in the city of Tampa, Florida, U.S. In addition to a basic visual assessment, a sampling of larger diameter (>30.5 cm) live oak (Quercus virginiana) and all large diameter laurel oak (Quercus laurifolia) trees were tested with a resistance-recording drill to determine the amount of decay present (looking specifically at the sound-wood-to-stem-diameter ratio). Overall, 56.9% of the trees tested had some level of decay, though the incidence of decay was higher in laurel oak (67.4%) than in the live oak (29.4%). Additionally, tree species (P < 0.01), diameter (P < 0.01), and the presence or absence of visual decay indicators (P = 0.03) were all significant predictors of decay presence.