Seize the Memory of Soil

a Citizen Science project on mapping soil moisture memory 

Soil Memory and Soil Moisture Memory

Plants, animals, and people live on the soil, but do you know that many organisms also live in the soil? Click on the figure below and print out the booklet (created by the Natural Resources Conservation Service - NRCS) to explore the underground world of life.

Soil is a living thing - it is very slowly moving, changing, and growing all the time. Soil breathes like humans and needs air and water to stay alive. Healthy, living soil provides us with our everyday needs, including not only food, grass, plants, and trees, but also medicines, paint, paper, ink, chalk, and shampoo just to name a few.

Soil has its memory and scientists can use selected features of the soil to tell its past environment. If you want to know what happened to the soils on a geological time scale (from tens of thousands of years to billions of years ago), you can measure the carbonate and carbon isotopes in the soil (a method used by archaeologists for carbon dating).

If you want to study soil memory on a much shorter time scale (from days to months ago), you can record the changes in soil moisture over time and calculate Soil Moisture Memory.

Soil Profile: Layers of different colors tell us about the soil's past environment

Why is Soil Moisture Memory important to our planet and society? 

Soil moisture controls plant growth, the temperature of the land surface, the duration of rainfall or flooding, and risks of drought and wildfire. A long soil moisture memory means that soil dries out slowly after rainfall, so the soil can memorize its past wet condition for a long time; a short soil moisture memory means that soil dries out quickly so the soil can only memorize its past wet condition for a short time.

 Knowing soil moisture conditions and soil moisture memory is very important for people to manage agricultural activities (e.g., irrigation) and improve forecasting of extreme weather events (drought, flooding, and wildfire). This is becoming extremely important as we will experience more frequent extreme weather events in the near few decades due to climate change.

Drought in California (Getty Images)

Flooding on Iowa farms (Iowa DOT)

What does soil moisture memory look like in different regions of the world?

 A recent study by scientists from MIT and NASA tracks soil moisture memory using satellite data. The figure below shows that soil moisture memory is different across the globe (pink color means longer memory). On average, about one-seventh of the amount of rain that falls is still present in the topmost layer of soil three days later and soil moisture memory is greatest in Earth’s driest regions (e.g., the western US, Sahara)

How can we increase/decrease soil moisture memory?

Scientific studies (1, 2, 3) have found that soil moisture memory is determined by many factors such as climate and plant. However, it is not well understood how soil controls soil moisture memory. As the impacts of climate change grow, we face decisions about how to respond. It is largely unknown how climate policies and sustainable soil management such as deforestation/reforestation and soil management (e.g., mulching, reduced tillage) could change soil moisture memory.

How could we measure soil moisture memory?

In this project, we will use a simple approach to directly measure soil moisture memory from the ground. We need support from Citizen Scientists like you to collect soil moisture data across the country and work through a number of science exploration tasks. Are you ready for the challenges and getting involved to seize the memory of soil?