Exploring Phosphorus Cycle Dynamics Along River Bottomlands

The impact of bottomland forest type on long-term nutrient cycling and loss in Clarks River National Wildlife Refuge in Kentucky.

Micromorphology of Clarks River soil elucidating dynamics of iron-manganese (Fe-Mn) and nutrient cycling. Plane-polarized light image (top) of soil thin section showing fine-grained soil matrix with quartz (Qtz) and fungal hyphae associated with edge of Fe-Mn concretion. Cross-polarized light image (bottom) from the subsoil Btg horizon showing Fe-Mn concretion with high-birefringent (b-fabric) clay oriented along the rim of the concretion (i.e., stress cutan). This feature may limit phosphorus adsorption or prevent phosphorus release from the concretion.

[Top image courtesy G. E. Stinchcomb. Bottom image re‌printed with permission from Stinchcomb, G. E., et al. "The Role of Oak Species in Long-Term Soil P Loss in a Humid River Bottomland." Catena 227 107125 (2023). DOI:10.1016/j.catena.2023.107125.]

The Science

Different forest types affect soil nutrient amounts in a humid area in Kentucky. Researchers examined two types of oak trees (post oak and cherry bark oak) and measured physical, chemical, and mineral properties of the soil in 12 different locations to see how much phosphorus was being lost from the soil and how different oak trees affected this loss. The oak tree with greater phosphorus demand had more loss of phosphorus from the soil because the tree’s roots took up more water, which caused the soil to expand and shrink and made it harder for the soil to hold onto phosphorus. There was more phosphorus loss in soil under post oak trees than cherry bark oak trees. Results showed that the type of clay in the soil was most likely not the main reason for this difference in phosphorus loss. Overall, this study shows that forest type can affect how much water and nutrients trees take up, which can impact the soil and ecosystem over time.

The Impact

This study could impact new frontiers in science related to understanding and managing ecosystems, especially those in humid areas with similar forest types. The findings suggest that forest type can affect nutrient cycling and loss, which can have significant impacts on the long-term balance of water and nutrient uptake in the ecosystem. This knowledge can be applied to better manage and protect forest ecosystems and to promote sustainable land use practices. Additionally, the study’s use of advanced sampling and measurement techniques could inform future research on soil health and nutrient cycling in other ecosystems, providing valuable insights for future environmental management efforts.


This study aimed to determine whether different forest types affect long-term cycling of soil phosphorus in subtropical river bottomlands. Researchers selected two forest ecosystems, post oak and cherry bark oak, as they are thought to differ in drought tolerance. Study sites had similar landscape positions, parent material, soil age, and climate. Results suggest a greater loss of phosphorus in soils underlying post oak compared to cherry bark oak. Analysis of tree samples showed similar leaf phosphorus content in both types of oak but significantly more phosphorus in the woody biomass of post oak than in cherry bark oak. The study suggests that post oak prioritizes storing phosphorus in woody biomass for efficient water use during dry periods and that phosphorus may be a limiting nutrient for post oak. This research highlights the importance of considering long-term effects of different tree types on nutrient and water balance in soil.

Principal Investigator

Bassil El Masri
Murray State University
[email protected]

Co-Principal Investigator

Gary Stinchcomb
Murray State University
[email protected]

Program Manager

Brian Benscoter
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
[email protected]


This research was supported by the U.S. Department of Energy (DOE) DE-SC0022228, U.S. Geological Survey 104b grants, and the U.S. Fish and Wildlife and Clarks River National Wildlife Refuge.


Stinchcomb, G. E., et al. "The Role of Oak Species in Long-Term Soil P Loss in a Humid River Bottomland." Catena 227 107125  (2023). https://doi.org/10.1016/j.catena.2023.107125.