Historic urban trees: assessment of the internal integrity of the stem

Abstract

In addition to the benefits that all trees provide, in general, the cultural and affective value that historic urban trees provide contributes to the quality of life in cities. As they age, care for their maintenance must be careful and constant, aiming to reduce the associated risks. Thus, the objective of the present study was to identify and estimate the extent of internal areas injured in the trunk of historic urban trees. Forty-five Eucalyptus robusta trees located in a popular square in the city of Nova Friburgo-RJ/Brazil were evaluated. A visual analysis of the crown, trunk, and root system was performed, followed by complementary evaluations of acoustic tomography and resistography, when necessary. Mathematical models were adjusted in order to infer the relationship and influence of dendrometric characteristics (total height, height to the first branch, diameter at 1.30 m above the ground, and crown diameter) and the mean resistographic amplitude on the mean wave propagation velocity acoustic. Most trees presented some type of external lesion on the trunk and, in general, trees with severe lesions also presented alterations in the propagation velocity of acoustic waves and in the perforation resistance profile. Thus, the combination of different assessment techniques helps in the identification of internal lesions in the trunk of urban trees, including mature and historical ones.