Herbaceous production as influenced by juniper canopy cover in west Texas



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Texas Tech University


Juniper encroachment and subsequent density and canopy cover increases on rangeland reduce herbaceous production beneath and outside of the canopy area. Associated problems are decreased water yield, reduced carrying capacity, higher erosion, and difficult livestock handling. The objective of this study was to quantify and correlate aerial phytomass production with different levels of redberry juniper {Juniperus pinchotii Sudw.) canopy cover, density, and canopy volume in west Texas. The Texas Tech Experimental Ranch (Borden County, TX) study sites were on a deep hardland range site with Olton clay loam soils. The Pitchfork Ranch (Dickens County, TX) sites were on a mixedland range site with very fine sand soils. The Stone Ranch (Tom Green County, TX) sites were on a clay loam range site with Angelo clay loam soils. The Triangle Ranch (Foard and Hardeman Counties, TX) sites were on a deep hardland range site with Tilhnan clay loam soils. Juniper canopy cover was measured with both line transects and belt transects. Aerial phytomass yield and relative frequency of grass species were estimated by clipping 0.25-m quadrats. Dominant grass species differed among locations. Line intercept canopy cover of redberry juniper was more highly correlated with herbaceous yield than the canopy cover estimates obtained with belt transects. Yield was reduced an average of 1,000 kg/ha as juniper canopy cover increased from 0 to 35%. Regression analysis predicted a yield reduction 33.5% and 50% at 20% and 40% juniper canopy cover, respectively. Yield reductions at 20% juniper canopy cover were greater on the two deep hardland range sites compared to the clay loam and mixedland ranges sites, but at 40% canopy cover, yield reductions were about equal across range sites. The largest decreases m yield occurred as juniper canopy cover increased from 0 to 15%, contrary to prior beliefs.



Rangelands, West Texas, Plant canopies, Juniper -- Control, Range plants