Community characteristics and population structure of Heptacodium miconioides Rehder within and around Nanhe National Nature Reserve, Hubei

Heptacodium miconioides Rehder (seven-son flower) is listed as a vulnerable species on the IUCN Red List of Threatened Species and is also included in the List of National Key Protected Wild Plants in China. This shrub or small tree was first recorded in 1907 by Ernest Wilson in western Hubei, central China, and was later found in Zhejiang and Anhui. However, for the next 115 years, it was not observed in Hubei and was presumed to be locally extinct. In August 2022, the species was rediscovered in the Hubei Nanhe National Nature Reserve, approximately 100 km from its type locality. The discovery site is characterized by typical deciduous broad-leaved forest, dominated by Carpinus stipulata H.J.P. Winkl., Platycarya strobilacea Siebold & Zucc., H. miconioides, and Quercus variabilis Blume. Our surveys identified 151 individuals across three localities at elevations of 1 000–1 300 m. The size class structure (main stem) of the rediscovered populations is spindle-shaped, suggesting a decline due to insufficient seedling recruitment. Of the 151 newly discovered individuals, 137 (91%) produced a total of 936 suckers, averaging 6.83 suckers per plant. This prolific sprouting may compensate for the lack of seedlings, helping to maintain populations and enabling species persistence in the niche. As these populations are located in remote mountain ridges and cliffs with minimal human disturbance, the population decline may be driven primarily by internal factors. We recommend additional field surveys to identify potential undiscovered populations, alongside a comprehensive conservation plan, including in situ conservation, artificial cultivation of seedlings, ex situ conservation, and reintroduction efforts.