Water use of Juniperus virginiana trees encroached into mesic prairies in Oklahoma, USA

Abstract

Juniperus virginiana (eastern redcedar) is encroaching into mesic prairies of the southern Great Plains, USA, and is altering the hydrologic cycle. We used the thermal dissipation technique to quantify daily water use of J. virginiana into a mesic prairie by measuring 19 trees of different sizes from different density stands located in north-central Oklahoma during 2011. We took the additional step to calibrate our measurements by comparing thermal dissipation technique estimates to volumetric water use for a subset of trees. Except for days with maximum air temperature below À3°C, J. virginiana trees used water year round, reached a peak in late May, and exhibited reduced water use in summer when soil water availability was low. Overall daily average water use was 24 l (±21.8 l s.d.) per tree. Trees in low density stands used more water than trees with similar diameters from denser stands. However, there was no difference in water use between trees in different density stands when expressed on a canopy area basis. Approximately 50% of variation in water use that remained after accounting for the factors site, tree, and day was explained using a physiologically-based model that included daily potential evapotranspiration, maximum vapour pressure deficit, maximum temperature, solar radiation, and soil water storage between 0 and 10 cm. Our model suggested that a J. virginiana woodland with a closed canopy is capable of transpiring almost all precipitation reaching the soil in years with normal precipitation, indicating the potential for encroachment to reduce water yield for streamflow and groundwater recharge.

Ecophysiological responses of native invasive woody Juniperus virginiana L. to resource availability and stand characteristics in the semiarid grasslands of the Nebraska Sandhills

“…J. virginiana in the dense stand maintained photosynthetic activity during the growing season and dealt with water stress by maintaining Ψw above a threshold (Willson et al 2008), due in part to the significantly smaller trees and canopy size in dense vs. open grassland despite the age difference between trees in the two sites, resulting from competition for resources, as well as self-pruning under low light conditions -height and crown volume in dense canopy were 30 and 77%, respectively, lower than in the open grassland. Awada et al (2013) and Caterina et al (2014) reported a positive functional relationship between sap wood area, tree diameter, canopy size, foliage and water use in J. virginiana. The higher water-use efficiency expressed by …”

“…J. virginiana is considered a drought tolerant species (Bihmidine et al 2010) and has the ability to maintain stomatal opening and photosynthetic activity at relatively low water potentials (Eggemeyer et al 2006, Willson et al 2008, reaching xylem cavitation and 50% loss of conductivity at Ψ w = -5.8 [MPa] in stems and Ψ w = -4.9 [MPa] in roots (Willson et al 2008), values that were not reached in this study. J. virginiana expands and survives in arid and semiarid environments because it has significant plasticity in water uptake (Eggemeyer et al 2009, Caterina et al 2014) and access to deeper soil layers (roots can reach 7 m deep) where water is available during the periods of low water availability (Walker and Noy-Meir 1982). That said, tree growth does not only depend on energy capture and photosynthetic rates, but also on the efficiency and effectiveness of carbohydrate integration, as well as the costs of maintaining and producing the photosynthetic system (Givnish 1988).…”

Calibration of SWAT model for woody plant encroachment using paired experimental watershed data

“…Recent studies reported excessive depletion of rooting zone soil moisture for eastern redcedar woodland in winter and early spring when the warmseason grass is still dormant (Zou et al, 2013;Caterina et al, 2014). Early work on plot-level Bowen ratio-energy balance method in the Edwards Plateau of Texas suggested that the actual evapotranspiration (ET a ) of Ashe juniper (Juniperus ashei) (similar to eastern redcedar) woodland was 35-85 mm higher than that of adjacent grassland on annual basis (Dugas et al, 1998).…”

Encroachment Dynamics of Juniperus virginiana L. and Mesic Hardwood Species into Cross Timbers Forests of North-Central Oklahoma, USA

“…The recent period ending in 2015 was the driest since 1975-1980, which may help explain the low numbers of J. virginiana in the current seedling size class. Juniperus virginiana transpires water all year in the Cross Timbers [13]. While extremely drought-tolerant, J. virginiana seedlings may be more susceptible to drought than larger J. virginiana trees because seedlings have smaller, shallower root systems.…”