Nucleation in temperate woodland regeneration: dual mycorrhizal Salix facilitate ectomycorrhizal tree establishment.

There is an urgent need for woodland expansion to help enhance and restore vital forest ecosystem services. However, the process of natural regeneration of woodlands is often slow, requiring active reforestation approaches. Factors limiting regeneration are complex, but there is increasing evidence that natural woodland expansion onto sites that have been treeless for a long period of time may be limited by the loss of microbial woodland‐soil properties. This study explored a potential role for mycorrhizal associations in facilitating obligate ectomycorrhizal (ECM) tree establishment, with potential implications for active reforestation practices. We determined the spatial distribution patterns of ECM tree seedlings – <italic>Pinus sylvestris</italic> and <italic>Betula</italic> spp. – outwith a woodland, in relation to existing dual‐mycorrhizal <italic>Salix</italic> plants. There was very strong evidence that ECM tree seedlings were more likely to be found growing within groups around <italic>Salix</italic> than as isolated individuals, supporting the view that <italic>Salix</italic> drives the current spatial distribution patterns of ECM tree establishment. We suggest that the ability of <italic>Salix</italic> to form dual AM and ECM associations allows it to become established across the open AM dominated vegetation. Over time these plants become colonised by ECM fungi via aerial spores and then can act as a source of inoculum for obligate ECM tree seedlings, which arrive as seeds in the vicinity of <italic>Salix</italic>. This study highlights the potential role of dual‐mycorrhizal <italic>Salix</italic> as a nurse plant in supporting secondary forest succession of obligate ECM boreal/temperate woodland species onto adjacent open areas through nucleation. Overall, we concluded that there is potential for existing ECM networks to aid tree establishment and propose a nature‐based approach to maximize reforestation efforts by targeting existing symbiotic fungal networks as nucleation points for tree planting. Our findings contribute to understanding the ecological dynamics involved in woodland expansion and restoration. [ABSTRACT FROM AUTHOR]