Sampling network
The present study is part of an ongoing citizen science project that
involved so far a total of 93 participants, including 41 scientists and
52 partner schools from 17 European countries (Castagneyrol et al.,
2019; Valdés-Correcher et al., 2021) covering most of the native
geographical range of the pedunculate oak (Figure 1A ). We
geolocalized and surveyed a total of 298 mature oak trees in forest and
urban areas during 2018 (n = 132), 2019 (n = 56), and 2020 (n = 113)
(Figure 1 ).