![]() ![]() The issue of juniper encroachment is complicated because plants are only one of the many interacting factors that influence how water moves underground. It is a very complicated problem to study," says Fred Pierson, a research hydrologist with the USDA Agricultural Research Service in Boise and a coauthor on on the 2005 paper. We do not know what effect the trees are really having on streamflow. "The whole streamflow question is still, in my mind, an open debate. However, in a 2005 review paper on juniper encroachment, Miller and his colleagues point out that this link hadnt been verified by scientific studies. If the trees were taking up such a large amount of water, certainly there would be less available groundwater for springs and streams. Ranchers tell of springs drying up or year-round channels losing their summer flow as junipers became abundant in a watershed.īarrett notes that enthusiasm for this theory gained momentum in the 1970's when studies by Miller showed that a mature juniper could draw 25-35 gallons of water a day. In a 2009 report for the Oregon Watershed Enhancement Board (OWEB), author Hugh Barrett describes a history of observations linking juniper encroachment to reduced spring and stream flow. In many cases, the trees outcompete understory plants for nutrients, water, and sunlight forming areas of bare soil between trees and exacerbating soil erosion. In Phase III, junipers dominate a site and form a dense stand with minimal understory plants. However, there can be less forage for cattle and less cover and food for sagebrush-dependent wildlife. ![]() In Phase II, junipers are mixed with woody and herbaceous vegetation, and wildlife diversity can remain high. In Phase I, shrub and grass species still dominate a site and wildlife diversity can remain high. Miller uses phases to describe the stages of juniper encroachment and their effects. ![]() Miller notes that other factors, such as climatic conditions and increasing levels of atmospheric carbon dioxide, have also aided the expansion of juniper woodlands. The fire suppression policies of the 20th century also allowed the spread of juniper to continue. Without fire, juniper woodlands began expanding into areas once dominated by sagebrush and aspen. "The biggest thing that livestock grazing did was reduce the fine fuel component in more productive sites where fire would reoccur," says Miller. Cattle cropped most of the grasses that normally becomes fuel for wildfires. In the 1880s, the introduction of cattle and consequent heavy grazing led to a decrease in the number of wildfires annually. He says about the junipers range: "If you are looking for old juniper trees, you go to sites that are on shallow soils that don't produce very much understory so there is not a lot of fuel to carry fire." Rick Miller, an Oregon State University rangeland ecologist, has spent his 33-year career studying juniper. Before European settlement, the junipers range consisted of isolated pockets where fire was uncommon. The vegetation community that dominates Eastern Oregon evolved to withstand periodic fire - even water-loving aspen that thrive in riparian areas are adapted to fire disturbance. Tim Deboodt, an Oregon State University extension agent in Crook County, describes this widespread problem: "If we want to restore streams and fish habitat.we need to have our backs to the creek and look at the problems upslope." The Problem - Land Use and Juniper Encroachment In Central and Eastern Oregon, the issue of juniper encroachment has become a main cause of many ecological imbalances, and restoration efforts must often must address the spread of junipers even when the project focuses on streams or rangelands. Managers are also concerned about the trees' impact on an area's water cycle, as the trees absorb much more water than native grasses or shrubs. This increase has land managers worried - juniper displaces native shrubs and grasses that provide forage for livestock and habitat for at-risk species like the sage grouse. In the last 130 years, however, there has been a tenfold increase in the acreage covered by juniper woodlands in Oregon. Western juniper, an iconic evergreen in the arid West, was once largely confined to rocky ridges and isolated patches on shallow soil. Knowing grass, I can appreciate persistence. Knowing trees, I understand the meaning of patience. ![]()
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