The Lost Forest Research Natural Area is a designated forest created by the Bureau of Land Management to protect an ancient stand of ponderosa pine in the remote high desert county of northern Lake County, in the south central area of the U.S. state of Oregon. Lost Forest is an isolated area of pine trees separated from the nearest contiguous forest land by forty miles of arid desert. There are no springs or surface water in Lost Forest, and much of the southwest portion of the natural area is covered by large shifting sand dunes that are slowly encroaching on the forest.
Geology
Lost Forest is located at the northeastern corner of the Christmas Lake Basin in south central Oregon. The bedrock beneath the area was created by basalt flows laid down during the Pliocene and Pleistocene epochs. After a period of intense faulting during the middle Pleistocene, a large basin area was created by erosion and sedimentation. This basin filled with water during the wet climatic periods of the Pleistocene and post-Pleistocene. Over the past 3,200 years, the surface water in the Christmas Lake Basin has completely dried up, leaving an arid high desert environment.
Today, the Lost Forest area is generally flat with gentle swales. The base elevation is above sea level. However, there are a number of basalt outcroppings that rise above the surrounding terrain. There are also large moving sand dunes in the southwest corner of the natural area. These dunes are made up of lacustrine sediments, Aeolian deposits, and alluvial materials with large amounts of volcanic pumice and ash mixed into fine sand. Most of the dunes occurred west and south of the Lost Forest; however, there has been some shifting of sand from the dry lakebed of Fossil Lake through portions of the pine and juniper stands in the southwest section of the natural area. Some trees have been killed and others partially covered and then uncovered later as the sand moved through the area. While the dunes kill some trees, they do not appear to threaten the forest in general.
Environment
Lost Forest covers approximately . It is a self-sustaining stand of ponderosa pines growing in the arid high desert, from the nearest contiguous pine forest. The Bureau of Land Management considers to be prime forest land with large old-growth trees dominating the stands. Lost Forest is a remnant of an ancient ponderosa pine forest that covered much of central Oregon thousands of years ago, when the climate was cooler and wetter. Today, the Lost Forest pines survive on half the annual precipitation normally required for their species. This is possible because of the unique soil and hydrologic properties of the Lost Forest area.
The natural area's deep sandy soil has helped the Lost Forest ponderosa pines survive in the arid high desert environment. The Lost Forest soil was formed from lake sediments and alluvial materials. Pumice sands from Mount Mazama and Newberry Crater appear in the surface soils throughout the Lost Forest area. The post-Pleistocene lake environment formed the ash sediments from Mount Mazama into porous ground soil. The soils are underlain by hard calcium carbonate caliche layer several inches thick. This subsurface layer is impervious to water drainage and is seldom penetrated by roots. As a result, ground water is held near the surface. The local ponderosa pines make use the moisture held in the porous soil above the caliche barrier. In addition, scientists have found that the pine seeds from the Lost Forest trees germinated more quickly than other ponderosa pine seeds, suggesting a local adaptation to the arid environment is now a common characteristic of the Lost Forest ponderosa pine community.
In addition to its ponderosa pines, the Lost Forest also supports a plant community that includes big sagebrush, antelope bitterbrush, and other shrubs as well as a number of desert grasses and flowering plants. Western juniper are also common in many parts of the natural area.
Ponderosa pines dominate the Lost Forest Research Natural Area, typically growing in open stands rooted in sandy soils. In some parts of the natural area, western junipers are sparse, covering less than one percent of the land. However, much of Lost Forest is characterized by co-dominance of ponderosa pine and western juniper. Some of the older junipers are very large. One specimen is the largest known western juniper in Oregon, reaching a height of . Bark beetle attacks and drought in the 1920s and the 1930s resulted in high juniper mortality from which the population has not fully recovered.