Karst is one of the most changeable landscapes on Earth. Karst is the word used to describe the landscape that forms when soluble rocks such as limestone and dolomite dissolve. The term comes from the German word for the Karst region on the border of Slovenia and Italy, although the word has a much longer history. The Karst Plateau was the first area where research on karst topography was conducted. Publishing in German in 1893, Serbian geographer Jovan Cvijić introduced the term into the modern age along with terms such as karren and doline.
Karst terrain is characterised by unique geomorphological features associated with the dominance of chemical weathering in the form of dissolution. These include sinkholes, limestone forest and pavement, pinnacles, towers, disappearing rivers and, of course, caves. The largest karst area in the world is the Nullabor Plain in Australia. Other important karst areas lie in Slovenia, Mexico and China.
Southern China is dominated by karst and subject to intensive agriculture. In 2015 my colleague Professor Tim Quine approached me about being involved in a grant application to study the fragile “critical zone” of the Chinese karst. The critical zone is the interface between rock and water, life, air and living organisms on the surface of the Earth, characterised, but not limited to the soil and interactions around it. My role would be to look at the rate of natural process associated with the production and transport of soil. The Chinese karst has been subjected to rocky desertification, which in this case refers to the removal of soil and consequently vegetation through erosion. I proposed to use cosmogenic nuclides to study the rate of bedrock erosion (and hence the rate of soil production) and the length of time that has elapsed to build up the soil cover.
The project was funded through the Natural Environment Research Council of the UK and the Newton fund. The latter promotes economic development and social welfare of developing countries. The project name was SPECTRA (Soil Processes and Ecological Services in the Karst Critical Zone of Southwest China). We conducted field work in 2016 and visited the farmed karst in Guizhou. The model above shows a typical area of the slope where the farmers have shifted soil to increase adjacent built-up beds to a more productive thickness. This exposes areas of limestone that have eroded under soil cover. I collected soil samples from undisturbed areas under forest and samples of rock from eroding outcrop from various locations around a single catchment. As these samples are analysed they will give us the first insight into how long it takes to generate this landscape and how long it would take to regenerate lost soil cover on this important agricultural area.