Pruning revisited – effect of pruning season on wood discoloration and occlusion in four temperate broadleaved tree species

Abstract

Abstract Pruning is a necessary part of tree management both in silvicultural systems and in urban forestry. For the wood industry’s production of high-quality timber, as well as for the urban forest’s risk reduction and ecosystem services enhancements, it is essential that the pruning is accurately implemented. This study aimed to determine the effect of pruning season on discoloration amount and occlusion rate in four broadleaved tree species. In 2014, 84 trees were pruned in January, May and September. Six years later, the 252 samples from the three pruning points per tree were collected and analysed. ‘Common oak (Quercus robur L.)’ and ‘small-leaved lime (Tilia cordata Mill.)’ showed least discoloration when pruned in January, ‘wild cherry (Prunus avium L.)’ showed least discoloration when pruned in September and ‘Norway maple (Acer platanoides L.)’ did not show any significant differences. All species occluded fastest when pruned in January, but at different rates. Common oak occluded 84 per cent of the samples, Norway maple 42 per cent, small-leaved lime 32 per cent and wild cherry 13 per cent. In summary, the pruning month affected discoloration amounts and occlusion rates of the tested tree species in varied ways. Our research suggests an important knowledge gap regarding optimal species-specific pruning times and underlying reasons for different reactions to pruning.