The implementation of biodiversity conservation measures in forests managed for timber production usually implies trade-offs between ecological and economic objectives. In continuous cover forestry these trade-offs emerge at the scale of selecting individual trees for timber harvesting or habitat retention. Tree selection determines both the economic viability of timber management and the prevalence of treerelated microhabitats, considered a multi-taxon indicator of forest biodiversity. Recent studies find that tree selection is influenced by several factors, such as individual management preferences and goals, professional education and institutional context. To gain a deeper understanding of tree-selection practices in the context of retention forestry, we analyse four tree-selection exercises on silvicultural training sites (Marteloscopes) performed by groups with different professional backgrounds: conservationists, foresters, and students of each. Based on qualitative data from participant observations and group discussions, we explore their decision-making strategies, reasoning, and practices. Our analysis provides novel insights into decision-making processes when implementing conservation measures, especially with regard to dealing with trade-offs and uncertainties. Our findings indicate that tree-selection decisions are not merely the result of cognitive and rational weighing processes. They can be understood as practices requiring experience, professional routine, and intuition. These practices differ across professional cultures. Despite these differences, the participants of the analysed Marteloscope exercises developed an understanding of the other stakeholders' motivations and restrictions. The setting stimulated a change of perspective that built awareness in many of the participants of their own routines and biases. This may facilitate professional cooperation, crossdisciplinary learning, and the implementation of biodiversity conservation.