Advancing Forest Soil Moisture Monitoring in the Daniel Boone National Forest

Soil moisture is a key ingredient for atmospheric, biological and hydrological processes. Evapotranspiration from the surface provides a significant moisture source to the atmosphere; soil water holding capacity and infiltration are fundamental components driving regional hydrology; and soil moisture within the root zone is essential for vegetation growth and health. The importance of this critical variable is now widely recognized, and the routine measurement of soil moisture is now common across many state weather observing networks.

Forests comprise approximately 34% of U.S. land area. Nevertheless, despite its importance, soil moisture is rarely, if ever, routinely measured within the forest environment. This is due to several factors unique to the forest environment: the difficulty of collecting weather data within the forest canopy; challenges obtaining power and accessing communications; and the complications of installing soil sensors within the root-heavy forest floor. In addition, complex terrain often accompanying forest regions further complicate installation and access to environmental monitoring stations.

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Beginning in 2020, Western Kentucky University’s Kentucky Climate Center, in collaboration with the U.S. Forest Service and U.S. Department of Agriculture, embarked on a 3-year project to develop best-practices on how to collect routine measurement of soil moisture within a forest environment. Specifically, this research project aimed to address the lack of data in mountainous, forested landscapes; better understand and document the nuances of sensor deployment and data collection within such areas; and develop a forest soil moisture climatology.

Now nearly complete, the Daniel Boone National Forest Soil Moisture Network is comprised of two research study areas. The Cumberland Ranger District Micronet, located in central Kentucky in Menifee County (Fig. 1), is anchored by a new Kentucky Mesonet station located 6 miles south-southwest of Frenchburg. The station measures air temperature, relative humidity, wind speed and direction, barometric pressure, precipitation, solar radiation, and soil temperature and moisture at 5 depths (2, 4, 8, 20 and 40 inches) (Fig. 2). In addition, a soil micronet of over 30 additional soil sensors (e.g., Fig. 3) are deployed in two nearby locations along northeast and southwest facing slopes.

The Redbird Ranger District Micronet, located in southern Kentucky in Clay County, near the town of Peabody, will soon be anchored by its own Kentucky Mesonet station. In addition, a soil micronet of over 30 additional soil sensors are deployed across five sample areas in the vicinity that represent a range of landscape positions and aspects. All data are collected, quality controlled, and archived in real-time.

Data from these networks are providing a basis for study and a foundation from which to learn, explore, and refine. Long-term, data from soil moisture networks such as these are improving hydrological monitoring, predictions, and ultimately, faster, more accurate warnings, and thereby saving lives, reducing property loss, and optimizing mitigation efforts.