Management of urban trees is key to sustaining and increasing essential ecosystem services, and most management decisions are made based on urban tree inventories. Vitality is one of the key parameters when conducting tree inventories. However, consensus on how vitality should be assessed is lacking, and there is limited understanding of how visual vitality assessments are affected by aspects of different professional background, growing sites and tree age. In a Delphi study with 19 participants completing the whole study, we asked urban foresters and ecologists to assess the vitality of 21 trees in urban and rural settings and to rate how important 40 different parameters were for their assessment of each tree’s vitality. The data obtained were analysed using Cronbach’s alpha, unconstrained ordination, hierarchal clustering and indicator values. In testing for differences, mixed general linear models and constrained ordination were used. Professionals participating in the study showed good overall agreement in ranking trees as more or less vital, but with large differences in what was considered a fully vital tree. When performing vitality assessments, the parameters used differed between old and young trees, and between urban and rural sites. There was also a systematic difference between urban foresters and ecologists in performing tree vitality assessments, with ecologists consistently rating tree vitality higher and using fewer parameters. Parameters used for assessing vitality comprised aspects relating to sign of decay, external damage, loss/death of biomass, growth performance and site conditions. Vitality should thus be regarded as a complex parameter that needs calibration-based assessment approaches and the person performing the assessment should always be included as an additional variable. Overall, this study clearly showed the need to establish consensus on how tree vitality should be assessed and rated.

城市树木的管理是维持和增加基本生态系统服务的关键，大多数管理决策都是基于城市树木清单进行的。生命力是进行树木调查时的关键参数之一。但是，关于应如何评估活力的共识尚未达成，并且关于视觉活力评估如何受到不同专业背景，生长地点和树木年龄的影响的了解也很有限。在由19名参与者完成的整个研究的德尔菲研究中，我们要求城市林业和生态学家评估21种树木在城市和乡村环境中的生命力，并评估40种不同参数对于评估每棵树木生命力的重要性。使用Cronbach's alpha，无约束排序，层次聚类和指标值对获得的数据进行了分析。在测试差异时，使用了混合的一般线性模型和约束排序。参与研究的专业人员在将树木列为或多或少至关重要的方面显示出良好的总体共识，但是在被认为是完全重要的树上却存在很大差异。在进行活力评估时，使用的参数在老树和幼树之间以及城乡之间是不同的。在进行树木生命力评估时，城市林务员和生态学家之间存在系统性差异，生态学家始终对树木生命力进行更高的评估，并使用更少的参数。用于评估活力的参数包括与腐烂迹象，外部破坏，生物量损失/死亡，生长性能和场所条件有关的方面。因此，活力应被视为需要基于校准的评估方法的复杂参数，并且执行评估的人员应始终被包括为附加变量。总体而言，这项研究明确表明有必要就如何评估和评估树木活力建立共识。