Red Soil CZ: From natural to anthropogenic evolution of Red Soil and its impact on ecosystem function in the Critical Zone

Red soils cover 20% of each of China and India, the most populated countries on earth, as well as large areas of developing countries in southeast Asia, Africa and South America. They form in sub-tropical climates where excessive leaching from rainwater has produced an infertile, unstable soil that is very vulnerable to mismanagement, climate change and pollution such as acid rain. In China, red soils support about 40% of the population, made possible through the intensive use of fertilisers to boost crop yields. This farming system is unsustainable; fertilisers reaching groundwater, freshwater and the atmosphere pose a significant environmental threat, and soil degradation through intensive cultivation can result in tens of tonnes of soil being eroded each year from a hectare of land into water courses during the intensive monsoonal, spring rains. Red soil management for agriculture affects local farmers who depend on them for their livelihood, the surrounding population who need them for food, China because of dependence for national food production and globally because of the area red soils covers, their importance for food production and the large environmental footprint.

Although extensive research has studied red soils, particularly related to management for agricultural sustainability, the integrated effects of various affected aspects of the critical zone, as well as the wider environmental impacts are poorly understood. In this proposal we adopt a critical zone approach, to reach beyond soil processes to encompass the atmosphere above, geology and groundwater below, surrounding freshwater and vegetation. By definition, the critical zone is the constantly evolving boundary layer at the surface of the earth where rock, soil, water, air and living organisms interact. Two essential components are essential for delivery. First, we have the major advantage of the Sunjia Critical Zone Observatory (CZO), the only international CZO in China where soil and water data have been collected since 2002. Second, we have assembled a team of Chinese and UK scientists who integrate a range of specialisations in soil science, with atmospheric, geological, hydrological and agronomical sciences. A skill gap identified amongst the Chinese partners in terrestrial environmental modelling is filled by the UK team, with training and joint positions proposed that will develop this capability in China.

We build on existing Sunjia CZO monitoring by incorporating subsurface and atmospheric processes not included in the past. Further experiments in the lab and the field will allow us to explore impacts of environmental threats such as climate change, water scarcity and acid rain. We span from processes involved in weathering minerals, how these minerals interact with life to form soils, and how we can optimise these processes in soil evolution for the benefit of the environment and food security. These processes then enhance our understanding of hydrological and erosion impacts in red soils induced by different management practices. Detailed monitoring of these processes in the Sunjia CZO and other red soil areas provides data that inform our modelling of ecosystem processes. This process benefits immensely from a critical zone monitoring data-set for red soils that will span almost 20 years by the end of the project.

The new science generated in this project, particularly the modelling outputs, provides valuable data for policy decisions in China about the management of red soils. We provide training to project partners in interdisciplinary science that is essential to CZO research and will benefit the research capabilities of the Chinese team. Moreover, we bring new skills to the Chinese team in terrestrial modelling. Coupled with our intended outcome of more sustainable food production from red soils, our training and government agency engagement ensures delivery of OECD Official Development Assistance from this project.

China is very aware of the importance of red soils and threats posed by their mismanagement. They established IRS, RSEES and provincial institutes to investigate red soils so that rural livelihoods and the environment can be improved through better land management. We contribute to the impact of this research by bringing together research areas that are somewhat fragmented in China by adopting a critical zone approach. Outcomes include an improved mechanistic understanding of red soil evolution and functioning, which informs upscaling and modelling.

Through this research we improve impact with government agencies, since outputs in terms of mapping and predictions will be produced that assist with regional scale decision making. Government agencies will be better able to assess threats posed by the current management of red soils, climate change and atmospheric deposition. Through interacting with UK scientists with experience working with UK, Europe and international agencies, Chinese government agencies and scientists will be exposed to different approaches to use science for evidence-based policy decisions. Likewise, experience gained by the UK scientists will benefit their government agency networks.

Such government policy decisions will then improve the rural livelihoods of people dependent on red soils and make their management more sustainable. We improve impact and the speed of uptake by working with established networks in China that provide agricultural advice, via IRS and RSEES in particular. Our new results will improve understanding of the wider impacts of different soil management approaches. These include very easy, low risk 'wins' that we can demonstrate for red soils, such as better fertiliser use and organic matter management. Inappropriate fertiliser use will be easy to rectify through government policies in China, so the evidence we provide, backed by UK researchers who have provided similar guidance for UK policy development, will help sway current policies of cheap, poorly controlled nitrogen application.
To farmers we also provide evidence of the benefits of different farming practices to inputs and yields. Our work builds on long-standing field trials that provide demonstration sites for agricultural advisors who can learn and then teach the effectiveness of managing organic matter and fertilisers more effectively, as well as the impacts of different crops on the environment.

We use the common approach ethos of the U.S. NSF CZO Program in our research in terms of: (1) resolving the evolution and formation of the CZ; (2) measuring the properties and structure of CZ; and (3) constructing the energy, water, solutes and sediment fluxes and balances from event to long-time scales (http://criticalzone.org/national/infrastructure/). Many common measurements to US and SoilTrec CZOs will be collected, contributing to the global data-sets and allowing for inter-site comparisons. Historical Sunjia CZO data-sets will be supplemented with greater monitoring of element and energy exchanges to the subsurface, atmosphere and vegetation. Red soils are important to countries with vulnerable food production outside China, particularly in Asia, Africa and South America, so we address a highly weathered, infertile soil that could be managed more effectively.
For the public we have impact through knowledge exchange via lectures, the media, a website and social media, as described in the Pathways to Impact. We will also benefit from the outreach activities already in place as part of other CZO networks, where we will seek an active role by providing material that is accessible by the public.

A large impact from our project will be scientist training in China. Through this project and workshops, they will learn about interdisciplinary approaches essential for CZO research, improve writing skills and be exposed to terrestrial modelling that we identified as a skill gap at the Chinese institutions involved.