Early Detection of Decline in Tree Health. Could the Pace of Stem Water Be an Effective Indicator

The health and vitality assessment of each single tree is one of the most important actions for an optimal urban forest management program. The development of new technology able to continuously monitor the tree vitality and underlying trends, could help reduce the frequency of the monitoring assessment and help overcome problems related to the rapid decline in tree health. Our aim was to test the suitability of point dendrometers in evaluating the tree vitality trend through high resolution stem cycle analyses. To achieve this objective, we installed point dendrometers on twelve Pinus radiata each currently in one of three defined vitality classes (alive, compromised, and dead) growing in an urban area. The stem cycle analysis approach was used to synchronize dendrometer signals with the stem water status and temperature. Our results showed that both, the trend of stem growth (GRO) and the time lag between the occurrence of the minimum temperature and the onset of the stem shrinkage, are all promising indicators of tree vitality in Pinus radiata. These parameters could be integrated in network systems able to send “early alerts” to experts. It could allow them to keep multiple trees under continuous monitor and control simultaneously, and reduce costs due to the reduced monitoring visits.