Rock outcrops (ROCs) in epikarst usually have large bulk, often stretching from the ground surface to the bedrock, and possess characteristics that differ from a non-limestone area. They play a unique, hydrological role in the infiltration and redistribution of precipitation. However, the effect of rock outcrops on water infiltration has not yet been well explored.
Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) applied dye tracers at the uphill sides, downhill sides, and lateral sides of the ROCs on a plot of sloping farmland. They aimed to explore water pathways of outcrop runoff and their ecological functions in epikarst.
The study was performed in Mengzi County, Yunnan Province, southwestern China
Their results showed that outcrop runoff penetrates deep along the soil–rock interface and expands laterally along the rock surface and into the surrounding soils in various proportions on the three sides of the ROCs (i.e., the uphill sides, the downhill sides, and the lateral sides).
At the uphill sides of the ROCs, deep but narrow vertical flow was the most common infiltration pattern of outcrop runoff. On the contrary, long but shallow lateral flow along the rock surface dominated the outcrop runoff movement on the lateral sides, and most of the applied water was distributed to the topsoil. However, on the downhill sides of the ROCs, the vertical flow at the soil–rock interface was quantitatively equal to the lateral flow into the soil (i.e., the ratio of WV/WL was close to unity).
The difference in outcrop runoff infiltration at the three sides of ROCs may help to reveal the mechanisms of soil erosion as well as rock dissolution and biodiversity in a karst environment.
The study entitled “Infiltration Patterns and Ecological Function of Outcrop Runoff in Epikarst Areas of Southern China” has been published in Vadose Zone Journal.
Prof. SHEN Youxin Ph.D
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China