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Three Forms of Soil Moisture Memory
Three Forms of Soil Moisture Memory
The overall soil moisture memory reflects how today's soil moisture is related to soil moisture from the past few days (e.g., yesterday or last week). The more similar today's soil moisture condition is to its past, the longer the overall soil moisture memory will be, and the longer the soil can hold its water over time. Calculation of overall soil moisture memory is very simple as it only requires us to measure soil moisture at a site on a regular basis for a period of time (e.g., daily measurements for two weeks). However, the overall soil moisture memory does not tell us the characteristics of the soil moisture memory, namely, what the weather condition is when the soil dries out in the field.
The overall soil moisture memory reflects how today's soil moisture is related to soil moisture from the past few days (e.g., yesterday or last week). The more similar today's soil moisture condition is to its past, the longer the overall soil moisture memory will be, and the longer the soil can hold its water over time. Calculation of overall soil moisture memory is very simple as it only requires us to measure soil moisture at a site on a regular basis for a period of time (e.g., daily measurements for two weeks). However, the overall soil moisture memory does not tell us the characteristics of the soil moisture memory, namely, what the weather condition is when the soil dries out in the field.
Short-term soil moisture memory reflects soil drying via drainage and fast evaporation. Longer short-term memory can lead to soil flooding after heavy rainfalls.
Long-term soil moisture memory reflects soil drying via slow evaporation. Longer long-term memory makes the plant better survive drought and heat waves.
The short-term and long-term soil moisture memories are somewhat similar to the overall soil moisture memory but they can tell us more information about the condition of the soil that loses its water over time. Short-term soil moisture memory is designed to quantify how fast soil dries out immediately after the rainfall stops (about 1-3 days). At this stage, you can find standing water on the ground surface, and water rapidly leaves the soil either downward (known as "drainage" and the soil is like a leaky bucket) or upward via evaporation from the soil and transpiration from the plant (known as evapotranspiration, or see Water Cycle diagram). The longer the short-term soil moisture memory, the longer the soil can hold its water after rainfall events, and the more likely the soil will become waterlogged or flooded, like the one that happened recently in Illinois, which delayed farmers' planting due to the difficulty of driving in the wet soils.
The short-term and long-term soil moisture memories are somewhat similar to the overall soil moisture memory but they can tell us more information about the condition of the soil that loses its water over time. Short-term soil moisture memory is designed to quantify how fast soil dries out immediately after the rainfall stops (about 1-3 days). At this stage, you can find standing water on the ground surface, and water rapidly leaves the soil either downward (known as "drainage" and the soil is like a leaky bucket) or upward via evaporation from the soil and transpiration from the plant (known as evapotranspiration, or see Water Cycle diagram). The longer the short-term soil moisture memory, the longer the soil can hold its water after rainfall events, and the more likely the soil will become waterlogged or flooded, like the one that happened recently in Illinois, which delayed farmers' planting due to the difficulty of driving in the wet soils.
Unlike short-term soil moisture memory, long-term soil moisture memory is designed to quantify how fast soil dries out several days later after the rainfall stops. During this period, you will find that the soil surface is dry and water moves slowly out of the soil via evapotranspiration. The longer this long-term soil moisture memory, the longer the soil can hold this water for an extended period of time, and the more likely plants can survive during a drought or heat wave event.
Unlike short-term soil moisture memory, long-term soil moisture memory is designed to quantify how fast soil dries out several days later after the rainfall stops. During this period, you will find that the soil surface is dry and water moves slowly out of the soil via evapotranspiration. The longer this long-term soil moisture memory, the longer the soil can hold this water for an extended period of time, and the more likely plants can survive during a drought or heat wave event.
Five Drivers of Soil Moisture Memory
Five Drivers of Soil Moisture Memory
Some researchers have investigated the various causes/drivers of soil moisture memory and discovered that soil moisture memory is controlled by five factors: soil characteristics, weather characteristics, the effects of weather conditions (e.g., rainfall, solar radiation) on soil moisture dynamics, the effects of soil moisture on water runoff (water flow over the ground surface, see Water Cycle diagram), and the effect of soil moisture on evapotranspiration. The two-way relationship between weather conditions and soil moisture is complex and an active research area, often known as "land-atmosphere interactions".
Some researchers have investigated the various causes/drivers of soil moisture memory and discovered that soil moisture memory is controlled by five factors: soil characteristics, weather characteristics, the effects of weather conditions (e.g., rainfall, solar radiation) on soil moisture dynamics, the effects of soil moisture on water runoff (water flow over the ground surface, see Water Cycle diagram), and the effect of soil moisture on evapotranspiration. The two-way relationship between weather conditions and soil moisture is complex and an active research area, often known as "land-atmosphere interactions".
A global Köppen–Geiger climate map (after Beck et al., 2018)
A global land cover/vegetation type map (by MODIS satellite)
How to Manage Soil Moisture Memory under a Changing Climate
How to Manage Soil Moisture Memory under a Changing Climate
Compared to natural factors that control soil moisture memory (e.g., weather and vegetation), human activities have become increasingly important in changing the water cycle and greenhouse gas emissions. By changing land cover and land use types such as reforestation and adopting sustainable soil management practices (e.g., crop rotation, cover cropping, reduced tillage, mulching, soil carbon sequestration), ecosystems can store more water and carbon in the soils, deliver better ecosystem services, and become more resilient under climate extremes such as drought and heat waves.
Compared to natural factors that control soil moisture memory (e.g., weather and vegetation), human activities have become increasingly important in changing the water cycle and greenhouse gas emissions. By changing land cover and land use types such as reforestation and adopting sustainable soil management practices (e.g., crop rotation, cover cropping, reduced tillage, mulching, soil carbon sequestration), ecosystems can store more water and carbon in the soils, deliver better ecosystem services, and become more resilient under climate extremes such as drought and heat waves.
As the impacts of climate change grow, we face decisions about how to respond. Explore the recent International Carbon "4 per 1000" Initiative and the U.S. Global Change Research Program (USGCRP) and see what can be done by our communities to make our planet more sustainable under climate change.
As the impacts of climate change grow, we face decisions about how to respond. Explore the recent International Carbon "4 per 1000" Initiative and the U.S. Global Change Research Program (USGCRP) and see what can be done by our communities to make our planet more sustainable under climate change.
Nationwide high-resolution soil moisture visualizing tool from the Crop Condition and Soil Moisture Analytics (Crop-CASMA)
How will these sustainable soil management practices and climate policies affect Soil Moisture Memory? The soil moisture datasets collected from this project by Citizen Scientists like you may help us better answer these questions. If you are also interested in these topics, visit the Tasks and get involved in the project.
How will these sustainable soil management practices and climate policies affect Soil Moisture Memory? The soil moisture datasets collected from this project by Citizen Scientists like you may help us better answer these questions. If you are also interested in these topics, visit the Tasks and get involved in the project.
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