Ecohydrologic Connections in Semiarid Watershed Systems of Central Oregon USA

An improved understanding of ecohydrologic connections is critical for improving land management decisions in water-scarce regions of the western United States. For this study, conducted in a semiarid (358 mm) rangeland location in central Oregon, we evaluated precipitation-interception-soil moisture dynamics at the plot scale and characterized surface water and groundwater relations across the landscape including areas with and without western juniper (Juniperus occidentalis). Results from this study show that juniper woodlands intercepted up to 46% of total precipitation, altering soil moisture distribution under the canopy and in the interspace. Results indicate that precipitation reaching the ground can rapidly percolate through the soil profile and into the shallow aquifer, and that strong hydrologic connections between surface and groundwater components exist during winter precipitation and snowmelt runoff seasons. Greater streamflow and springflow rates were observed in the treated watershed when compared to the untreated. Streamflow rates up to 1020 L min(-1) and springflow rates peaking 190 L min(-1) were observed in the watershed where juniper was removed 13 years ago. In the untreated watershed, streamflow rates peaked at 687 L min(-1) and springflow rates peaked at 110 L min(-1). Results contribute to improved natural resource management through a better understanding of the biophysical connections occurring in rangeland ecosystems and the role that woody vegetation encroachment may have on altering the hydrology of the site

The effect of western juniper on the estrous cycle in beef cattle

Numerous evergreen trees and shrubs contain labdane acids, including isocupressic acid, which can cause late-term abortions in cattle. Recent research has shown that the bark from western juniper trees can also cause late-term abortions in cattle. Additionally, ranchers have observed that cattle in western juniper-infested rangelands tend to have decreased conception rates. The objective of this study was to determine if western juniper alters the estrous cycle of cattle. Fourteen heifers (10 treated and 4 control) were monitored for 74 days for signs of normal estrous behavior, with a 21 day feeding trial with western juniper bark from days 28-48, after which the cattle were bred naturally with a bull. The cattle were checked for pregnancy 30 days after all cattle had been bred. The data from this study indicate that exposure to western juniper bark does not affect normal estrus, estrous cycle or conception rates of cattle.Keywords: Cattle, Isocupressic acid, Estrus, Abortion, Western juniper, Estrous cycl

Overstory–Understory Vegetation Cover and Soil Water Content Observations in Western Juniper Woodlands: A Paired Watershed Study in Central Oregon, USA

The effects of western juniper (Juniperus occidentalis) control on understory vegetation and soil water content were studied at the watershed-scale. Seasonal differences in topsoil (12 cm) water content, as affected by vegetation structure and soil texture, were evaluated in a 96-ha untreated watershed and in a 116-ha watershed where 90% juniper was removed in 2005. A watershed-scale characterization of vegetation canopy cover and soil texture was completed to determine some of the potential driving factors influencing topsoil water content fluctuations throughout dry and wet seasons for approximately one year (2014⁻2015). We found greater perennial grass, annual grass, and shrub cover in the treated watershed. Forb cover was no different between watersheds, and as expected, tree canopy cover was greater in the untreated watershed. Results also show that on average, topsoil water content was 1% to 3% greater in the treated watershed. The exception was during one of the wettest months (March) evaluated, when soil water content in the untreated watershed exceeded that of the treated by <2%. It was noted that soil water content levels that accumulated in areas near valley bottoms and streams were greater in the treated watershed than in the untreated toward the end of the study in late spring. This is consistent with results obtained from a more recent study where we documented an increase in subsurface flow residence time in the treated watershed. Overall, even though average soil water content differences between watersheds were not starkly different, the fact that more herbaceous vegetation and shrub cover were found in the treated watershed led us to conclude that the long-term effects of juniper removal on soil water content redistribution throughout the landscape may be beneficial towards restoring important ecohydrologic connections in these semiarid ecosystems of central Oregon

Evaluation of the Seasonal and Annual Abortifacient Risk of Western Juniper Trees on Oregon Rangelands

On the Ground • Western juniper trees can cause late term abortions in cattle, similar to ponderosa pine trees. • Results from this study demonstrate that there is no difference in the labdane acid (the abortifacien tcompounds) content of western juniper trees throughout the year, or from year to year. • Consequently the abortifacient risk of western juniper trees should not vary throughout the year, or from year to year. • Producers who winter cattle in rangelands with western juniper trees should take similar precautions to prevent late term abortions as they would with ponderosa pine trees.The Rangelands archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform March 202