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) The spatial dynamics of redcedar proliferation and its impact on water budget across a regional hydrologic network; (ii) the temporal dynamics of precipitation interception by the herbaceous canopy; (iii) the impact of redcedar infilling into deciduous forests such as the Cross Timbers and its impact on water budget and water availability for non-ecosystem use; (iv) land surface and climate interaction and cross-scale hydrological modeling and forecasting; (v) impact of redcedar encroachment on sediment production and water quality; and (vi) assessment and efficacy of different redcedar control measures in restoring hydrological functions of watershed.

No abstract

No abstract

The meteorological droughts in the climate transition zone of the Great Plains of the USA are projected to intensify, potentially leading to major shifts in water provisioning services in rangelands. To understand how meteorological drought interacts with vegetation to regulate runoff response, we collected precipitation, root zone soil moisture, and runoff data from experimental grassland and juniper (Juniperus virginiana L., redcedar) woodland watersheds for five years encompassing a drought year to pluvial year cycle. We contrasted the frequency distribution of precipitation intensities and applied wavelet analysis to reveal the coherence between precipitation and root zone soil moisture patterns. Compared with grassland, the root zone soil moisture in woodland had a narrower range, with the peak frequency skewed to a lower soil moisture content. The conversion of herbaceous vegetation to evergreen juniper woodland results in a delayed response of runoff to precipitation due to reduced antecedent soil moisture. The reduction of streamflow from the woodland watershed was greater in the normal and pluvial years than in the drought year. Thus, conversion from grassland to evergreen woody vegetation prolongs the impact of meteorological drought on soil moisture and streamflow. Restoring prairie that is heavily encroached by woody species may serve as an adaptive measure to mitigate the climate change impact on water resources and other ecosystem services provided by rangeland.