Relationships Between Western Juniper (Juniperus occidentalis) and Understory Vegetation

Abstract

Western juniper has been actively invading sagebrush plant communities for about 130 yr. Western juniper canopy cover generally increases as western juniper invades sagebrush steppe communities and succession progresses toward a western juniper woodland. Our goal was to estimate the impact of juniper invasion and canopy increase on understory vegetation structure and productivity on 101 sites in northeastern California. The primary objectives of this study were to: (1) examine the influence of increasing western juniper canopy cover on the composition and productivity of understory vegetation; and (2) assess the effects of western juniper removal on understory vegetation. Sites in early, mid-, and late successional stages and sites on the same soils that had not been invaded were selected. Sites where western juniper had been removed by prescribed fire, mechanical, or chemical methods were compared to adjacent untreated sites. Western juniper canopy cover, understory cover and species composition, productivity, and bare ground were determined at each site during May through July 2005 and 2006. Regression analysis was used to evaluate the relationship between western juniper canopy cover and understory vegetation parameters. Logistic regression was used to detect understory differences between treated (juniper removed) and untreated (juniper not removed) sites. A significant relationship was found between western juniper canopy cover and understory species richness, shrub cover, forb cover, total grass cover, cheatgrass cover, herbaceous productivity, and bare ground. Removal of western juniper increased total grass cover, cheatgrass cover, and productivity, and reduced bare ground. The results of this study support findings by researchers in other states that western juniper influences plant community structure and productivity, and removal of western juniper might reverse these changes in structure, but also might increase opportunities for invasion of cheatgrass.

Greater sage‐grouse use of mechanical conifer reduction treatments in northwest utah

“…Our results also corroborate other studies reporting that conifer removal improves habitat quality for sage‐grouse or leads to an increase in sage‐grouse use (Commons et al , Coultrap et al , Frey et al , Roundy et al ). Coultrap et al () found that removing junipers from the landscape resulted in increased grass cover and herbaceous productivity and reduced bare ground.…”

“…Our results also corroborate other studies reporting that conifer removal improves habitat quality for sage‐grouse or leads to an increase in sage‐grouse use (Commons et al , Coultrap et al , Frey et al , Roundy et al ). Coultrap et al () found that removing junipers from the landscape resulted in increased grass cover and herbaceous productivity and reduced bare ground. Roundy et al () demonstrated that shrub and perennial grass cover can be maintained when PJ woodlands are removed before displacing desired understory species (Phases I and II), but that treatments implemented when PJ was the dominate vegetation (Phase III) resulted in herbaceous‐dominated plant communities (Miller ).…”

Effects of using ground redberry juniper and dried distillers grains with solubles in lamb feedlot diets: Growth, blood serum, fecal, and wool characteristics1

“…Condensed tannins and volatile oil in redberry juniper can affect the animal and rumen function (Kumar and Singh, 1984;McIntosh et al, 2003). If DDGS and redberry juniper can effectively be used in lamb feedlot diets, it would not only reduce sheep production costs but may ultimately result in greater rangeland forage production and ecosystem health due to greater removal of juniper trees (Coultrap et al, 2008).…”

The Use of Low-Altitude UAV Imagery to Assess Western Juniper Density and Canopy Cover in Treated and Untreated Stands

“…Intensive grazing, reduced fire occurrence, and favorable wetter climate conditions have all been cited as reasons for the vast juniper expansion observed in the late 19th and early 20th century [3,5].Juniper expansion is a concern in many rangeland areas as it may lead to reduced water availability for other types of vegetation. Increased juniper canopy cover has been associated with increased bare ground and decreased shrub, forb, and grass cover [6] and reductions in vegetation production and diversity [7]. Several studies [6,[8][9][10][11] have addressed the impacts of juniper expansion on ecological and hydrological processes.…”

“…Increased juniper canopy cover has been associated with increased bare ground and decreased shrub, forb, and grass cover [6] and reductions in vegetation production and diversity [7]. Several studies [6,[8][9][10][11] have addressed the impacts of juniper expansion on ecological and hydrological processes. These impacts include increased erosion and runoff [12][13][14] and decreased soil moisture [8] typically associated with shifts in vegetation cover [2,12,15], particularly with increased bare ground in intercanopy locations [16].The use of ground-based techniques to assess vegetation characteristics is limited to the resources available and normally includes an aggregate of data collected at point specific locations.…”