Investigations on health condition of street trees after discontinued use of de-icing salts on streets in Berlin [Germany]

The health condition of street trees in Berlin was valuated basing on their outward appearance and analytically investigated at locations where such investigations had been conducted already some time ago. It was very obvious from the results that the discontinued use of de-icing salt on streets since the winter period 1981/82 has led to a significant improvement of the constitution of street trees. Only very occasionally there are still some relics of the former damages caused by salt stress. The conspicuous improvement of health condition agrees with the reduced contents of chloride and natrium in the leaves of street trees. Analyses of samples from several consecutive years have revealed that the reduction of chloride was retarded distinctly in relation to that of natrium. Although they appear to be healthy at the present time, formerly heavier damaged trees still contain higher concentrations of chloride - compared to those in an unstressed environment - in their leaves, whereas the concentration on natrium corresponds to the 'normal' rates by now. Only exceptionally we found increased concentrations of natrium in leaves of trees which are partially still now damaged by former influence of salt. In formerly heavier damaged trees the reduction of the concentrations of salt components has been reduced in speed in relation to those formerly damaged in a lesser degree. The reduction of salt stress could also be demonstrated by soil analyses. The contents of chloride had already been minimized after the first winter period without de-icing salt. In contrast has the reduction of natrium been much slower, and there are significant relations to soil conditions. The results of the investigations show once more that a renunciation of de-icing salt means a revitalization of formerly even seriously damaged street trees. They strongly support the requirement for general renunciation of the use of de-icing salts and for the introduction of an 'alternative' way of clearing streets from snow and ice as an essential for soil conservation and environmental precautions, esp. for the rescue of street vegetation inside towns