Diversity and abundance of large old trees in Hainan Island: Spatial analysis and environmental correlations

Abstract

Large old trees (LOTs) are invaluable natural treasures and cultural legacies, holding ecological, historical, social, and economic significance. However, climate change and human impacts threaten their existence. Understanding their species composition, age structure, biomass, and distribution patterns in relation to environmental factors is essential for effective conservation. In Hainan Island, South China, we analyzed 1081 LOTs from 74 species across 35 families, using a combination of field surveys and government data. The dominant families were Moraceae, Sapindaceae, and Fagaceae, with key species including Ficus altissima, Litchi chinensis, and Tamarindus indica. The age distribution followed a reverse J-shape, indicating a prevalence of trees aged 300–399 years. In contrast, diameter at breast height (DBH) and height distributions were unimodal, favoring medium to large-sized trees. Spatial analysis revealed uneven distribution patterns: the western zone exhibited the highest species diversity, the central zone moderate diversity, and the eastern zone low diversity, reflecting uneven urban and agricultural impacts. Most LOTs were concentrated at elevations of 0–50 m. Factors such as GDP, urbanization, and forest cover positively correlated with LOT abundance and diversity, with forest cover and average annual temperature particularly favoring these trees. The findings emphasize the intricate relationship between environmental factors and LOT distribution. They advocate for tailored conservation strategies that address the complex interplay of ecological, socioeconomic, and cultural influences on their preservation. Abstract in Chinese is available with online material.