1. INTRODUCTION
Population structure and its dynamics are fundamental to understand and
predict population development and critical for the conservation of rare
and endangered species (Harcombe 1987, Ezard et al. 2010, Salguero-Gomez
and Gamelon 2021). Quercus chungii is a tree species of Fagaceae,
endemic to China, and rare and endangered in Fujian Province (Wang et
al. 2011, Jiang et al. 2019, Sun et al. 2021). The distribution area and
population size of Q. chungii drastically reduced in the last
century due to extensive logging for its high-quality timber (Wang et
al. 2011). Previous work has focused on the community structures ofQ. chungii forest communities, and spatial genetic pattern and
distribution, seed production and germination of Q. chungii population (Chen 2004, Huang et al. 2010, Li et al. 2010, Wang et al.
2011, Huang et al. 2017, Jiang et al. 2019, Sun et al. 2021). However,
large knowledge gaps remain about its age or size structures and
temporal change, and its key demographic rates across age classes.
Understanding the population structure and its temporal dynamics ofQ. chungii is crucial for conserving and restoring Q.
chungii population and its associated communities and ecosystems.
Age structure and life table are important tools to study population
demographics (Harcombe 1987, Ezard et al. 2010, Jones 2021). We can
infer reproductive strategy and predict population development from age
structure by presenting the number of individuals in different
developmental stages of a population. The information of age structure
can be further used to construct a life table by calculating the key
population parameters, such as age-specific survival and mortality
probabilities. Thus, life table is a fundamental tool to explore
the heterogeneity of demographic processes across population
developmental stages and predict population dynamics and structures (Harcombe 1987, Jones 2021). Static or period life table is
often used for long-lived species as it is difficult to track
individuals from birth to death for such species (Jones 2021).
It focuses on the fate of a population with mixed age classes during a
particular time period. We can derive survivorship and mortality
curves (Harcombe 1987) from life tables to assess mortality risks across
age classes. There are usually three types of survivorship curves. Type
I is a convex curve, indicating an increasing risk of death with age.
Type II is a declining line, indicating a constant risk of death over
all ages. Type III is a concave curve, indicating a decreasing risk of
death with age. Survivorship curves of long-lived, slowing-growing tree
populations may not exactly fall into the three above types, but show a
mix of them (Harcombe 1987).
Seeds are essential for population survival and development, as they
determine seed plant reproduction and represent the start of any seed
plants ( Willson al. 2014). Although seed data are crucial for
population analyses of plant species (Adams et al. 2005, Salguero-Gomez
and Gamelon 2021), they are rarely incorporated into life table analyses
of tree populations. Since seed data are usually difficult to obtain,
most previous studies on tree population life tables set seedlings or
sapling as the starting stage (Farahat 2020, Wei et al. 2020, Ta et al.
2021, Wu et al. 2021, Zhang et al. 2023). Ignoring seed stage may result
in inaccurate assessment and prediction of population demographics.
This study focuses on the population structure and its temporal change
of Q. chungii in the Fujian Minqing Huangchulin National Nature
Reserve, which was established in 1985 to better conserve Q.
chungii and its associated communities and ecosystems (Li et al. 2010).
We aim to study the following questions: (1) What is the current
population structure of Q. chungii ? (2) How do the population
structures change from 2013 to 2023? (3) How does the mortality risk
change across size classes? We surveyed population of Q. chungii in both 2013 and 2023, and compared their temporal changes in population
structures. We estimated the number of germinated seeds from a previous
study on seed rain of Q. chungii . We assessed the mortality risks
across size classes by deriving survivorship and mortality curves from
the static life table. This study would improve the understanding of
current status and the prediction of the future development of Q.
chungii population, thus providing important guidance for the
conservation of Q. chungii .