ASSESSING THE RELATIONSHIP BETWEEN TREE DIMENSIONS IN AN URBAN ENVIRONMENT

Abstract. Urban forests can provide vital environmental and social functions if appropriately planned and managed. Tree inventory and tree dimensions are an important part of evaluating and monitoring the growth, size and health condition of urban trees. Accordingly, crown diameter (cd), height (h) and diameter at breast height (dbh) are significant biometric descriptors of tree size and bulk.

When making decisions regarding urban environments it is important to be able to properly estimate these descriptors which are also needed to evaluate for example the so-called zones of upheaval (i.e., areas of interaction between roots and hard surfaces) and soil volume needs for planting trees in urban areas as well as for estimating their growth, control of diseases and preservation requirements.

In line with the above, the scope of this contribution is that of assessing the relationship (via direct field measurements and regression analysis) that exists between the dbh of a given tree species relative to its h and cd. This information can be of assistance when substantiating tree measurements determined via existing mobile mapping technology systems.

One hundred and three mature Norfolk Island pine trees (Araucaria heterophilla) located along a tourist shoreline of the Gold Coast (Queensland, Australia) were selected for this work. Their h, cd and dbh were individually measured, processed, and mapped in terms of their coordinate locations (i.e., latitude and longitude). Tree data was captured via field surveys using a diameter tape for dbh, and a laser range finder for measuring tree h and cd. A GNSS enabled digital camera was used to collect pictorial information and location description.

For the case study investigated here, the regression models of h=F(dbh) and cd=F(dbh) reasonably validated (R²=0.928 and R²=0.899 respectively) the Australian standard estimates of h and cd of ornamental trees based on their dbh, thus making these estimates easier to determine via simplified mathematical functions. This is because the dbh is easier to be measured accurately in the field as compared to h and cd, and it can also provide information regarding the biomass, volume and carbon storage of trees.