Predicting the age of ancient trees and the factors influencing their growth of Lychee trees (Litchi chinensis)

Heritage trees possess significant ecological, historical, and landscape value within urban built environments. Predicting the tree age by tree size can enhance heritage tree registration and the development of public policy for heritage tree conservation. However, the relationship between the size and age of ancient trees is still unknown. This study aims to explore the best-fitted models that predict the relationships between tree age and breast and base girth of ancient lychee tree (Litchi chinensis) in China, and factors influencing the growth. The results indicate that there are 5629 ancient lychee trees. This study proposes recognizing lychee tree with a breast height girth of 1.31 m and a base height girth of 1.74 m or more as ancient. The random forest model identified socioeconomic factors as determining factors for ancient lychee tree growth. This study has significant implications for the heritage conservation of ancient lychee trees.