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Mixed-conifer forests of western red cedar, western white pine, mountain hemlock, fir and spruce are found throughout the mountainous west from eastern Washington through western Montana. Mild, dry summers and cold, snowy winters make for short growing seasons. In general, weakly developed soils are formed from a variety of materials, including granite, basalt, volcanic ash and sedimentary rocks. Cooperative LTSP work between the Forest Service's Rocky Mountain (formerly Intermountain) and Pacific Northwest Research Stations and the Intermountain, Rocky Mountain and Pacific Northwest Regions is underway in Idaho and eastern Oregon.
The upland oak-hickory forest is the single most extensive forest type in the nation south of Alaska. Covering over 114 million acres from central Texas, north to the Dakotas, and eastward to the Appalachian Mountains, this forest is found in all topographic positions with moist subhumid to dry subhumid climates. Soils often are gravelly and are formed from a variety of materials of glacial and sedimentary origin. LTSP collaboration between the Forest Service's North Central Research Station and the Eastern Region is just underway in Missouri, Indiana and Illinois.
More than 80 percent of the eastern aspen cover type grows on 13 million acres of commercial forest land in the Great Lakes region. Soils range from well-drained sands to poorly-drained clays. This forest type, characterized by gentle topography, humid, warm summers, and cold, continental winters, will be studied in Minnesota, Michigan and Wisconsin through the LTSP efforts of the Forest Service's North Central Research Station and the Eastern Region.
The Forest Service's Southern and Southeastern Research Stations and Southern Region are directing their work toward loblolly pine, the most commercially important forest tree in the southern United States. While this species grows on nearly 29 million acres in humid, warm temperate regions from eastern Texas to the Valley and Ridge Provinces of the Appalachian Highlands, forest on Coastal Plain sediments are the most important. Research is underway on sites that include excessively drained sands in Texas, medium-textured sites in Louisiana and Mississippi, and poorly-drained sites in North Carolina.
California's forests are extremely productive. Although accounting for only 3 percent of the nation's commercially forested land, this state has played a major role in meeting our nation's needs for forest products. In terms of productive capacity, only Oregon and Washington rank higher.
In California, LTSP research centers on the mixed-conifer forest. This forest type occupies 9.3 million acres (40 percent of our forested land). The first experimental site (the nation's second) was established in 1991 at the Challenge Experimental Forest, operated by the Forest Service's Pacific Southwest Research Station. Since then, other have been established. And by 1995, a dozen installations should be operating across the western slopes of the Sierra Nevada and Cascade Ranges.
Besides a standard set of measurements to be recorded at all installations, the California sites are providing valuable insights into rates of soil erosion, soil faunal activity and organic matter cycling in response to site disturbance. The effectiveness of both conventional and innovative recovery treatments also are being tested.
The National LTSP study will establish a landmark towards understanding how ecosystems respond to disturbance. Its findings will provide forest managers with the tools they need to sustain and improve forest productivity.