Tree architecture models, canopy maintenance, and associated root problems of angsana (Pterocarpus indicus Willd.) in the urban trees of Yogyakarta

Abstract

Troll's architecture model of angsana (Pterocarpus indicus Willd.) serves as a shading tree in most of the main roads in Yogyakarta. However, its lateral roots potentially damage sidewalks and cause accidents to people. This research was aimed to understand the damage types associated with the root problem, the relationship between stem diameter and root development, and angsana maintenance. Data were collected during January-July 2015 by inventory, tree identification, and interview. We categorized the types of damage into three scales, respectively: scale 1. Cracks in pots if the trees grow in pots, slight cracks on the road surface; scale 2. Roots start to slightly appear on the road surface and cause cracks in the road or damage the pots; scale 3. Roots appear on the road surface and cause a bend that harms road users or pots raised by roots. There is a relation between the size of stem diameter and its damage. Angsana starts to cause damage with a diameter of 20-29 cm on the divider and 30-39 cm on the sidewalk. We suggest that i) angsana should be planted in areas where the roots could grow freely, ii) applying alternate planting between the young and the old angsana, iii) root cutting.