A novel way of measuring tree vitality in mature urban trees

2010 | Dr. Denise Johnstone, University of Melbourne

The benefits of trees in urban environments include generating oxygen, removing pollution and absorbing carbon dioxide, among many others. However, predicting the health or vitality of trees quickly and in an objective manner, and thus maximizing the benefits of urban trees, can be problematic.  One of the methods used to assess tree vitality is the measurement of the ratio of leaf variable chlorophyll fluorescence to maximum fluorescence (FvFm). However leaf fluorescence should be measured on fully exposed sun leaves, which are difficult to access in mature trees. The objective of this study is to test a novel method of measuring the bark FvFm ratio of selected smooth barked trees. In order to test the method bark FvFm will be compared with leaf FvFm and a visual vitality index.

Study Results

Looking at whether there is a relationship between visual crown condition and leaf chlorophyll fluorescence – we found evidence of this with regard to all three tree species; Ficus macrophylla, Platanus xacerifolia and Ulmus parvifolia. We found good evidence for a relationship between bark chlorophyll fluorescence and visual crown condition in Ulmus parivifolia, but not in Ficus macrophylla or Platanus xacerifolia. We found little evidence that there is a relationship between leaf water potential and leaf chlorophyll fluorescence. Somewhat surprisingly we did find evidence to support our hypothesis that there is a relationship between leaf water potential and bark chlorophyll fluorescence in Ficus macrophylla and Platanus xacerifolia, but not in Ulmus parivifolia.

It appears that bark chlorophyll fluorescence measurements may offer a useful tool for tree vitality and/or assessment of the water status of individual urban tree species but further work is required to confirm the usefulness of bark chlorophyll fluorescence in this context.

For more information on this project, contact the researcher via TREE Fund at treefund@treefund.org.