It was found that the laurel, nettles and ferns that live in Tiankeng thrive on the abundant nutrients such as nitrogen, phosphorus, potassium, calcium and magnesium. These nutrients are scarce in other environments and limit plant growth. However, because these nutrients are abundant in Tiankeng, plant Chinese Journal of Plant Ecology
“Plants can adapt to harsh environments by adjusting their nutrients,” the researchers wrote in their paper, translated from Chinese using Google Translate.
Very little light reaches the bottom of Tiankeng, which means “heavenly hole” in Chinese, a 100-metre-deep hole in the karst landscape of southwest China. Research has revealed that the deep hole is home to plants that love moisture and shade, including species that are endemic to the region.
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“Tiankeng’s towering cliffs and rugged terrain have left it less affected by human activities,” the researchers wrote.Choerospondias axillaris ) and Chinese rain bells (Strobilanthes cucia ), they wrote.
For the study, the researchers collected samples from 64 plant species in and around Tiankeng in Leye County, Guangxi Zhuang Autonomous Region, China, which is home to the geological marvel, the Dashiwei Tiankeng Complex. Contains 30 sinkholes
Plants grown inside the tiankeng had a lower carbon content than plants grown outside, but had higher concentrations of all other elements the researchers measured, including calcium and potassium, and also had higher growth rates.
Chinese rain bells (Strobilanthes cucia Assam indigo (Assam indigo) is a modern karst plant found at the bottom of a sinkhole in China. (Image credit: dnixdony via Getty Images)
Carbon is essential for plants, making up much of their “skeleton” and structure that helps them retain water, according to the study. But the humid environment inside the mine means that plants don’t need to retain as much water, and can therefore function with lower levels of carbon in their tissues. Plants growing on the surface contain more carbon, likely because “the forest outside the mine has stronger light, faster evaporation, poorer soil, more human disturbance, and more susceptible soil loss,” the researchers write.
Plants growing inside the Tiankeng had higher nitrogen and phosphorus contents than plants on the surface, both of which plants absorb from the soil. The soil at the bottom of the Tiankeng contained more of these elements than the soil on the surface, indicating that plants are absorbing these elements more readily. Karst soils are rich in calcium and magnesium, and the Tiankeng plants showed much higher levels of these elements than the surface plants. The Tiankeng plants also had higher levels of potassium, despite the fact that karst soils are relatively low in potassium.
Research has shown that sinkhole plants are better able to absorb nutrients than “conservative” surface plants because nutrients are more abundant in the deep, shady areas of sinkholes, forcing plants to grow higher.
“The soil within Tiankeng Forest is in good nutrient condition,” the researchers wrote, and plants have evolved to make the most of the available resources, growing faster and collecting more light.
