The emergence of rock outcrops is very common in terrestrial ecosystems, especially in karst ecosystems. These outcrops are thought to redistribute most of the precipitation water to nearby soil patches and to exert certain impacts on soil water content. However, few quantitative studies have been conducted on rock outcrops, which made it difficult to evaluate their effect on water distribution to nearby soil patches.
Prof. SHEN Youxin and his student collected precipitation water and runoff water on the surface of carbonate outcrops in Shilin in southwestern China for 1 year. They aimed to determine the amount of water received by rock outcrops and subsequently the amount exported to nearby soil patches in different seasons and in different karst ecosystems (a rock desertification ecosystem, an anthropogenic forest ecosystem, a secondary forest ecosystem). They then wanted to assess the ecological significance of the water output.They used a rock emergence ratio of 30 and 70 % ground surface to evaluate the significance of runoff water, since 30 % is the lowest criterion for rock desertification.
The study showed that a large amount of input water was received by rock outcrops and 41-49% of it was transferred to nearby soil patches. The result indicated more than half of the water received by rock outcrops was channeled to other places, where it played various roles. The ratio of water export to water input varied slightly among the three systems. The researchers also found that a large rock outcrop emergence ration, such as 70%, would result in a sharply increased funnel effect toward nearby soil patches.
Runoff water along with the nutrients it contained was exported to nearby soil patches and consequently influenced the soil and plants that grew on it. When the emergence ratio of rock increased in karst ecosystem, water redistribution by means of rock runoff not only supplemented the soil with water and water-borne nutrients but also created water heterogeneity and nutrient heterogeneity in patchy soil, which may serve to explain the reason for karst biodiversity. 
The study entitled “Rock outcrops redistribute water to nearby soil patches in karst landscapes” has been published online in Environmental Science and Pollution Research.

Contact
Prof. SHEN Youxin  Ph.D
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
Tel: 86-871-65160910
E-mail: yxshen@xtbg.ac.cn

Runoff water collection systems (Image by WANG Dianjie)