The Jiang Nan subtropical evergreen forests ecoregion (WWF ID: IM0118) covers the mountainous divide between the lower Yangtze River and the coastal plain of South China.

The rugged limestone karst hills have been relatively protected from conversion to agriculture, and support specialized plant and animal communities.

The mountains separate the lower Yangtze River watershed to the north from the coastal plain to the south.

Parts of the mountains sit on granite, but much of the region is limestone, with distinctive pinnacles and karst terrain.

[2] Elevations over 1,000 meters feature semi-deciduous forests dominated by ring-cupped oak (Quercus glauca), Cinnamomum, Chinese elm (Ulmus parvifolia), and Bridelia.