ACADEMIA Letters Most important structural changes in a shrub community of deciduous oak forest in Hungary Tamás Misik, Eszterházy Károly Catholic University Introduction Shrubs of forest communities change dynamically and respond sensitively to the environmen- tal changes (Chipman & Johnson 2002; Rees & Juday 2002). They are strongly related to the structure and composition of the canopy layer (De Grandpré et al. 1993; Klinka et al. 1996). Shrub layer play a major role in the cycles of some essential nutrients, including the dynam- ics of N, K and carbon (Gilliam 2007). The shrub communities are directly contributes to forest biodiversity (Kerns & Ohmann 2004; Aubin et al. 2009), including compositional and structural diversity, enhancing the aesthetics of forest ecosystems and helping to protect wa- tersheds from erosion (Alaback & Herman 1988; Halpern & Spies 1995; Muir et al. 2002). There are only a few reports published on long-term monitoring of the shrub layer in oak forests (Alaback & Herman 1988; Chapman et al. 2006; Gracia et al. 2007; Gazol & Ibáñez 2009; Chapman & McEwan 2016). Serious oak decline began in 1979–80, heavily afecting Quercus petraea Matt. L. individuals, and resulting remarkable structural changes of shrub community in the forest. Material and methods The 27 ha nature reserve research site, the Síkfőkút forest is located in the Bükk Mountains (47°55฀N, 20°46฀E) in Hungary. Monitoring activities started in 1972 and it was repeated in 4-5 years period. The shrub layer was divided into a low (lower than 1.0m) and a high layer Academia Letters, December 2021 Corresponding Author: Tamás Misik, misiktom@gmail.com Citation: Misik, T. (2021). Most important structural changes in a shrub community of deciduous oak forest in Hungary. Academia Letters, Article 4459. https://doi.org/10.20935/AL4459. 1 ©2021 by the author — Open Access — Distributed under CC BY 4.0