Environmental drivers and conservation implications of endangered ancient Zelkova schneideriana trees in Hunan, China

There are many ancient Zelkova schneideriana trees that are over one hundred years old in Hunan Province, China, which have cultural and ecological values. However, the distribution, growth status and determinants of these Z. schneideriana remain to be explored. We collected data on the location and growth status of Z. schneideriana from the Information Management System of Ancient and Precious Trees in Hunan Province. Then, Average Nearest Neighbor and kernel density analysis were applied to investigate the distribution patterns and characteristics of Z. schneideriana. The potential distribution area and habitat suitability of Z. schneideriana were studied using the MaxEnt model. Finally, the factors affecting the distribution and growth status of Z. schneideriana were analyzed. The results showed that there were 501 Z. schneideriana in Hunan Province, distributed in 34 counties of 10 prefecture-level cities. The spatial distribution of these Z. schneideriana was clustered, with Chengbu Miao Autonomous County and Xinhuang Dong Autonomous County being high-density distribution areas. More than 60% of Z. schneideriana occurs at altitudes between 400 and 800 m. The most important factor influencing its population distribution is solar radiation in May (Srad5), followed by precipitation in the driest month (Bio14), with the total contribution of 82.63%. Specifically, when Srad5 > 15,544 (KJ/ (m² × day)) and Bio14 < 24 mm, the area is not suitable (LOV < 0.2) for the growth of Z. schneideriana. In various habitats, Z. schneideriana exhibits differences in growth conditions and tree characteristics. The highest number of Z. schneideriana (68.66%) are found along rural roadsides, but they grow in poorer conditions, are negatively impacted by road construction, and have lower tree height and crown width than that in other habitats. The size of Z. schneideriana is influenced by intraspecific competition, with scattered Z. schneideriana being taller and larger. These results can provide guidance for the conservation, management and tourism development of Z. schneideriana.