SREL Reprint #3879

Exploring forest structural controls on soil and litter evaporation via experimental simulations

Tyler E. McIntosh1,2, C. Rhett Jackson2, Caren C. Mendonca1, Seth E. Younger2, and Doug P. Aubrey1,2

1Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, USA
2Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, USA

Abstract: Evaporation from soil and litter (Esl) is a key but poorly understood component of forest evapotranspiration (ET), with its magnitude influenced by atmospheric conditions, forest structure, and forest management. We simulated the relative influence of canopy shade and leaf litter accumulation on Esl using full factorial manipulations (shade = 0, 40, 71, 91%; litter = 0, 200, 400, 800 g m-2) over lysimeters in a well-drained sandy soil. To isolate forest structural effects, Esl was measured under primarily energy-limited conditions, and to control for changing atmospheric conditions, Esl was relativized (ERel) using bare soil Esl (ERef), which was positively related to potential ET (ET0), vapor pressure deficit, and solar radiation (r2 = 0.93, 0.96, and 0.83). Averaged across litter levels, canopy shade reduced ERel by 17 to 32% relative to no shade, and averaged across shade levels, litter accumulation reduced ERel by 21 to 52% relative to no litter. Empirical relationships between Esl and ET0 generated coefficients (Ke) that declined as shade and litter increased, supporting a muted but persistent coupling of Esl with atmospheric drivers. Both canopy shade and litter accumulation independently influenced Esl; however, evidence suggests litter exerts stronger mechanistic control than shading. Specifically, the highest level of litter reduced ERel more than the highest level of shade, and the decrease in Ke was generally larger as litter increased than as shade increased. These findings reveal that litter accumulation plays a dominant mechanistic role in  moderating Esl and suggest that maintaining accumulated litter may be an effective management strategy for minimizing soil water loss.

Keywords: Canopy shade; Forest evapotranspiration partitioning; Hydrologic components; Litter accumulation; Lysimeter; Forest floor evaporation; Water budget

SREL Reprint #3879

McIntosh, T. E., C. R. Jackson, C. C. Mendonca, S. E. Younger, and D. P. Aubrey. 2026. Exploring forest structural controls on soil and litter evaporation via experimental simulations. Agricultural and Forest Meteorology 385(111222).

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).