Impact of eastern redcedar proliferation on water resources in the Great Plains USA – current state of knowledge

Authors: ZOU, CHRIS - Oklahoma State University; TWIDWELL, DIRAC - University Of Nebraska; BIELSKI, CHRISTINE - University Of Nebraska; FOGARTY, DILLON - University Of Nebraska; MITTELSTET, AARON - University Of Nebraska; Starks, Patrick; WILL, RODNEY - Oklahoma State University; ZHONG, YU - Oklahoma State University; ACHARYA, BHARAT SHARMA - Louisiana State University

Submitted to: Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2018
Publication Date: 12/1/2018
Citation: Zou, C.B., Twidwell, D., Bielski, C.H., Fogarty, D.T., Mittelstet, A.R., Starks, P.J., Will, R., Zhong, Y., Acharya, B. 2018. Impact of eastern redcedar proliferation on water resources in the Great Plains USA – current state of knowledge. Water. 10(12). https://doi:10.3390/w10121768.
DOI: https://doi.org/10.3390/w10121768

Interpretive Summary: In the U.S. Great Plains, water resources are derived primarily from surface runoff and local recharge from rangelands. These rangelands are under rapid transformation to woodland cover, principally by the encroachment of eastern redcedar (redcedar; Juniperus virginiana) trees. In this manuscript, the current understanding and impact of redcedar encroachment on the water budget and water resources available to support human activity are reviewed. Existing studies concluded that the conversion from herbaceous-dominated rangeland to redcedar woodland increases precipitation loss to canopy interception and vegetation transpiration. Additionally, the decrease of soil moisture is widely documented. The depletion of soil moisture is directly related to the observed decrease in surface runoff, and decreases recharge of underlying aquifers. Model simulations suggest that complete conversion of the rangelands to redcedar woodland at the watershed and basin scale in the south-central Great Plains would lead to reduced streamflow throughout the year, with the reductions of streamflow between 20 to 40%, depending on the aridity of the climate of the watershed. Recommended topics for future studies include: i) Assessing the spatial dynamics of redcedar proliferation and its impact on water budget across a regional hydrologic network. ii) Assessing the temporal dynamics of precipitation interception by the herbaceous canopy. iii) Determining the impact of redcedar infilling into deciduous forests, such as the Cross Timbers area, on water budget and water availability. iv) Evaluation of cross-scale hydrological modeling and forecasting taking into account land surface and climate interactions. v) Determining the impact of redcedar encroachment on sediment production and water quality. vi) Assessment and efficacy of interventions that prevent loss in hydrological functions compared to traditional eastern redcedar controls.

Technical Abstract: In the Great Plains of the central United States, water resources for human and aquatic life rely primarily on surface runoff and local recharge from rangelands that are under rapid transformation to woodland by the encroachment of eastern redcedar (redcedar; Juniperus virginiana) trees. In this synthesis, the current understanding and impact of redcedar encroachment on the water budget and water resources available for non-ecosystem use are reviewed. Existing studies concluded that the conversion from herbaceous-dominated rangeland to redcedar woodland increases precipitation loss to canopy interception and vegetation transpiration. The decrease of soil moisture, particularly for the subsurface soil layer, is widely documented. The depletion of soil moisture is directly related to the observed decrease in surface runoff, and the potential of deep recharge for redcedar encroached watersheds. Model simulations suggest that complete conversion of the rangelands to redcedar woodland at the watershed and basin scale in the south-central Great Plains would lead to reduced streamflow throughout the year, with the reductions of streamflow between 20 to 40% depending on the aridity of the climate of the watershed. Recommended topics for future studies include: i) Assessing the spatial dynamics of redcedar proliferation and its impact on water budget across a regional hydrologic network. ii) Assessing the temporal dynamics of precipitation interception by the herbaceous canopy. iii) Determining the impact of redcedar infilling into deciduous forests, such as the Cross Timbers area, on water budget and water availability. iv) Evaluation of cross-scale hydrological modeling and forecasting taking into account land surface and climate interactions. v) Determining the impact of redcedar encroachment on sediment production and water quality. vi) Assessment and efficacy of interventions that prevent loss in hydrological functions compared to traditional eastern redcedar controls.