Large and old trees play an important ecological role in the landscape. They are homes to a large number of species of lichens, mosses, fungi, birds, bats and invertebrates. When planted in avenues along roads the trees can also for example hold cultural and aesthetic values and function as dispersal corridors for animals and plants. However, large and old trees are becoming less common in the landscape today. Knowledge about existing avenues, their condition and values is essential for planning, management measures and to maintain biodiversity and increase road safety. In Sweden, the Swedish Transport Administration (STA) has collected data about existing avenues along roads since the early 2000s. STA:s data collection is restricted to trees along the state road network and have its focus on traffic safety, biological, cultural and aesthetical values. Policies, planning and strategic questions about avenues and tree management have been managed internally within the STA and in collaboration with other authorities. Since 2007, biologists have surveyed avenues and solitary, large trees in southwest Sweden. All state roads in the region are now mapped, and each object is regularly revisited. The data is used as support in the annual maintenance of the trees. We present data from these surveys, and discuss strengths and weaknesses with the method used.We briefly present the Swedish national collaboration initiative for avenues and tree management, including its policy statement. We further discuss general challenges and opportunities with monitoring and maintaining tree avenues and solitary trees.
Tree avenues, solitary trees, roads, monitoring, maintenance, biodiversity