Andrews Forest LTER

Perennial research themes at the Andrews Forest LTER site include successional changes in forest ecosystems spanning 500 yrs; population dynamics of forest stands; forest-stream interactions; patterns and rates of decomposition; disturbance regimes in forest landscapes and watersheds; and hydrology at multiple scales.

The research program has been diverse throughout the history of the Andrews Forest, with many dominant themes persisting over the years, but also with attention to current issues in science and society. Emphasis in the 1950's centered on development of road systems and harvest of old-growth forests, and assessment of their effects on watersheds. Research in the 1960's focused on effects of logging on water, sediment, and nutrient losses from small watersheds. During the International Biological Program of the 1970's, basic studies centered on the structure and function of forest and stream ecosystems, particularly in old-growth forests. In the 1980's, these basic studies continued under LTER funding and were augmented with applied research in silviculture, wildlife, landscape ecology, and other topics.

The central question currently guiding the Andrews Forest LTER studies is: How do land use (mainly forestry and roads), natural disturbances (mainly fire and floods), and climate change affect three key ecosystem properties: carbon dynamics, biodiversity, and hydrology? These three ecosystem properties are of high scientific and social interest, and they represent three rather different types of ecological response to landscape patterns. The research is organized in Component Areas of traditional, disciplinary focus, such as carbon dynamics, hydrology, and disturbance, and Synthesis Areas, which integrate work over several Component Areas. The Andrews Forest program also includes a strong partnership of the research community with the land managers of the Willamette National Forest. We work together to develop and test new approaches to management of forests, watersheds, and landscapes, based on the most current science findings.

Located at 44.2 degrees north latitude and 122.2 degrees west longitude, the Andrews Forest is in the western Cascade Range of Oregon in the 15,800-acre (6400-ha) drainage basin of Lookout Creek, a tributary of Blue River and the McKenzie River. Elevation ranges from 1350 feet (410 m) to 5340 feet (1630 m).

The maritime climate has wet, mild winters and dry, cool summers. At the primary meteorological station near headquarters at 1400 feet (430 m) elevation, mean monthly temperature ranges from near 34 degrees F (1 degree C) in January to 64degrees F (18 degrees C) in July. Average annual precipitation varies with elevation from about 91 inches (230 cm) at the base to over 140 inches (355 cm) at upper elevations, falling mainly in November through March. Rain predominates at low elevations; snow is more common at higher elevations. Highest streamflow occurs generally in November through February during warm-rain-on-snow events.

When it was established in 1948, the Andrews was covered with virgin forest. Before timber cutting began in 1950, about 65% of the Andrews Forest was in old-growth forest (400-500 years old) and the remainder was largely in stands developed after wildfires in the mid-1800's to early 1900's. Clearcutting and shelterwood cuttings over about 30% of the Andrews Forest have created young plantation forests varying in composition , stocking level, and age. Old-growth forest stands with dominant trees over 400 years old still cover about 40 percent of the total area. Mature stands (100 to 140 years old) originating from wildfire cover about 20 percent. Wildfire was the primary disturbance in the natural forest; windthrow, landslides, sites of concentrated root rot infection, and lateral stream channel erosion were secondary disturbances. Lower elevation forest are dominated by Douglas-fir, western hemlock, and western redcedar. Upper elevation forests contain noble fir, Pacific silver fir, Douglas-fir, and western hemlock. Low- and mid-elevation forests in this area are among the tallest and most productive in the world. Average heights are in excess of 75 m and a typical stand stores in excess of 600 megagrams of carbon per ha.

These forests are also noteworthy for the large amounts of fine and coarse woody debris they contain. As elevation increases, Douglas- fir and western red cedar decline in importance and western hemlock is gradually replaced by Pacific silver fir. Non-forest habitats include wet and dry meadows, rock cliffs, and talus slopes. Rapidly flowing mountain streams are the primary type of aquatic ecosystem in the Andrews Forest. Streamflow follows the precipitation pattern with winter maximum flows three orders of magnitude larger than summer minimum. First and second-order streams under natural conditions are dominated by coarse woody debris and receive-a large annual input of litter which provides the energy base for the aquatic organisms. Larger order streams have a higher proportion of the energy base provided by in-stream photosynthesis, but litter inputs and coarse debris remain important components of all stream ecosystems.

In terms of biological diversity, the Andrews Forest supports a rich flora and fauna for a north temperate ecosystem. More than 500 vascular plant species are known to occur on the Andrews Forest, and the nearby RNA's include more than 100 additional species. Typical 0.5-ha plots in the upland sites include 35 to 40 species of vascular plants and riparian sites twice that number. Over 3,400 arthropod species have been reported, which probably represent slightly more than half the estimated total. About 20 species of reptiles and amphibians, seven species of fish, and 50 species of mammals are found on the Andrews. Over 70 species of birds are known to nest here. Plant and animal species associated with old-growth forests of the Pacific Northwest, including Vaux's swift and the northern spotted owl, are especially well represented. Other vertebrate species include pileated woodpecker, black bear, mountain lion, black-tailed deer, and Roosevelt elk.

Andrews LTER program has become a major center for analysis of forest and stream ecosystems in the Pacific Northwest. Today, several dozen university and Federal scientists use this LTER site as a common meeting ground, working together to gain basic understanding of ecosystems and to apply this new knowledge in management policy.

The Andrews LTER program has its roots in the establishment of the H. J. Andrews Experimental Forest by the US Forest Service in 1948. This began two decades of predominantly Forest Service research on the management of watersheds, soils, and vegetation. With the inception of the International Biological Programme-Coniferous Forest Biome (IBP-CFB) in 1969, university scientists began to play increasingly important roles in the Andrews program. The focus shifted from single disciplines to more integrated research on forest and stream ecosystems, especially old-growth forests. IBP-CFB ended in the late 1970s and LTER commenced in 1980. The first decade of LTER work developed a backbone of long-term field experiments as well as long-term measurement programs focused on climate, streamflow and water quality, and vegetation succession. Development of data and information management systems as part of the science program has been a major accomplishment. During LTER3 (1990-1996) we continued these long-term projects, but placed increasing emphasis on integration under the central theme: Develop concepts and tools needed to predict effects of natural disturbance, land use, and climate change on ecosystem structure, function, and species composition.