Physiologically-Linked Indices of Rainfall Variation Predict Water Stress For Central U.S. Tree Species

Multiyear measurements enable researchers to predict impacts of precipitation regimes on central U.S. deciduous forest trees.

The Science

Long-term measurements at an AmeriFlux site in Missouri have enabled researchers to understand and predict how precipitation regimes affect water stress levels for key plant species in a central U.S. deciduous forest.

The Impact

How precipitation regimes affect water stress levels for plant species with contrasting water use strategies is not well understood. This study establishes a simple approach to quantifying plant physiological drought and the ecological impacts of precipitation regimes. This approach will be useful in predictions of forest response to climate change.


Variations in precipitation regimes can shift ecosystem structure and function by altering frequency, severity, and timing of plant water stress. Being able to predictively understand impacts of precipitation regimes on plant water stress is crucial in a changing climate. The research team, led by Oak Ridge National Laboratory (ORNL), formulated complementary, physiologically-linked indices of precipitation variability (PV) and related them to continuous measurements of predawn leaf water potential—a fundamental indicator of plant water status—in six tree species with different water use strategies in a central U.S. forest. These indices explained nearly all interannual variations in water stress levels for all species. These species differed in sensitivities to variations in precipitation regimes with the differences more pronounced in response to PV than to amount. Further, they exhibited stress tradeoffs between low and high PV, suggesting that how different plant species respond to PV is part of species-specific water use strategies in a plant community facing the uncertainty of fluctuating precipitation regimes. The new indices provide simple ways to quantify physiological drought and the ecological impacts of precipitation regimes in a changing climate.

Principal Investigator(s)

Lianhong Gu
Oak Ridge National Laboratory


This work was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Biological and Environmental Research, Climate and Environmental Sciences Division. ORNL is managed by the University of Tennessee (UT)-Battelle, LLC, for DOE under contract DE-AC05-00OR22725.


Gu, L., S. G. Pallardy, K. P. Hosman, and Y. Sun. 2016. “Impacts of Precipitation Variability on Plant Species and Community Water Stress in a Temperate Deciduous Forest in the Central US,” Agricultural and Forest Meteorology 217, 120–36. DOI: 10.1016/j.agrformet.2015.11.014.