11institutetext: Knowledge-based Systems and Document Processing Research Group Faculty of Computer Science Otto-von-Guericke-University Magdeburg 11email: katrin.krieger@ovgu.de
We established two permanent plots in the nature reserve to survey the population of Q. chungii in 2013. One plot is 40 m × 40 m located near Tangxia village, and the other is 20 m × 30 m located at Fengshiling. We measured every tree with a DBH (diameter at breast height) ≥ 2.5 cm within the plots in 2013.
To assess the temporal changes in population structures, we re-surveyed the population in the two permanent plots in 2023. To obtain a more complete structure of population, we measured all individuals, including seedlings with a DBH \(<\ \)2.5 cm, within the permanent plots. We established four additional 20 m × 20 m plots near Tangxia village in the nature reserve to measure all individuals ofQ. chungii. Thus, in 2023, we surveyed the population structure of Q. chungii in a total area of 3800 \(m^{2}\) with dense distribution of the focal species.
2.3. Population age structure
We used the size structure of Q. chungii to represent its age structure, as it is difficult to directly measure age from such a rare and endangered tree species and size structures are commonly used to infer population age structures of tree species (Harcombe 1987, Wei et al. 2020, Ta et al. 2021, Wu et al. 2021, Zhang et al. 2023). We separated the population into seven age classes based on the estimated relationship between tree age and size from logged Q. chungii in this nature reserve (Yang 2005) and previous studies on the growth (Liu 2005) and population structures