Measurements of canopy interception and transpiration of openly-grown eastern redcedar in central Okalhoma

Abstract

Eastern redcedar (Juniperus virginiana L.) is rapidly encroaching and degrading native prairie and rangeland landscapes in the Great Plains of the U.S. Little is known concerning the impacts of increasing redcedar density and areal coverage on local and regional water budgets through transpiration (T r ) and canopy interception (C I ) of precipitation. Limited T r and C I studies have been conducted in dense stands of redcedar but results from these studies may not be applicable to redcedar growing in open environments. Four redcedar trees (two large, two small) were located in central Oklahoma to measure T r . Two limbs (one on the north face and one on the south face) on each of the large trees were instrumented with sapflux sensors to measure T r from August 2010 through mid-July 2012. Limb level T r was scaled to tree level T r using ratios of both leaf and bole areas. Whole tree T r was measured on two small redcedar trees from mid-May 2011 through mid-July 2012. Transpiration of the small redcedars was found to respond quickly to precipitation events, while the large redcedars did not. Redcedar T r was compared to that of native grasses. The large redcedars exhibited higher T r rates than native grasses while the small redcedars transpired at rates closely matching native grasses. Four different redcedars were instrumented to measure C I from October 2009 through mid-July of 2012. Redcedar canopies were found to intercept 100% of precipitation for events ≤ 2.4 mm. Redcedar canopies reduce annual precipitation received at the surface by about 33%, and as much as 39% in the western portion of the state. Significant canopy interception of precipitation, coupled with T r rates as large as or larger than native grasses and with year-round T r , suggests increases in redcedar density and areal coverage could affect local water resources (e.g. reducing infiltration, runoff, and ground water recharge rates).

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

“…However, recent studies emphasized differences in both ecophysiological characteristics and soil physical and hydrological properties associated with woody encroachment compared to forests. Although juniper trees are usually shorter than pine trees, the canopy interception of juniper can be 2-3 mm higher than any other species in the region including the oak trees (Owens et al, 2006;Starks et al, 2014). The stomatal conductance was set at 0.001-0.002 m/s based on field measurement by Will et al (unpublished data), which is lower than pine trees that are typically 0.002 m/s.…”

“…Starks et al (2014) showed that redcedar maximum canopy storage (CANMAX) was about 2.4 mm in an open environment. Our measurements showed a range of 2.14-3.44 depending on stage of canopy closure (manuscript in review).…”

“…The greater accumulation of biomass and litter aboveground in redcedar stands result in higher rainfall interception, with as high as 35-37% of total precipitation being intercepted by the juniper canopy and litter layer (Owens et al, 2006). Starks et al (2014) showed that redcedar canopies could intercept 100% of precipitation for events less than 2.4 mm.…”

Woody Plant Encroachment Impacts on Groundwater Recharge: A Review

“…Canopy and litter interception affect local recharge of groundwater by modifying the net precipitation and thus the net water input to the soil. Studies on interception loss to woody plants include [32,109,[118][119][120][121], among others. One such study found that woody plants have higher canopy storage capacity for rainfall compared to grassland [109].…”

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

“…This trend has accelerated in recent decades (Wilcox 2010, Twidwell et al 2013) modifying and in some cases threatening key ecosystem services (Norris et al 2001, Throop et al 2012, including biodiversity (Pierce and Reich 2010), species distribution and composition (Dobson et al 1997, Chapin et al 1998, Norris et al 2007, ecosystem NPP (Wilcox 2010), herbaceous (Ganguli et al 2008) and livestock production (Throop et al 2012), nutrient cycling (Archer 2010, Pierce andReich 2010), and system ecohydrology (Eggemeyer et al 2009, Awada et al 2013. There is much to be learned about the implications of shifts from open grasslands and savannas to closed-canopy woodlands on water and biogeochemical cycles (Wilcox 2010, Starks et al 2014, and the feedback of these cycle and resource availability changes on plant ecophysiological performance. Furthermore, investigating the seasonal and spatial physiological activity are necessary for modeling efforts including the estimation and forecasting of energy, water and carbon exchange, as well as NPP of a plant community and its projected dynamics in the face of climate variability and change (Hamada et al 2016).…”