Andrews Forest LTER

The Andrews Forest LTER has long been a dynamic and integrated program of research, education, and outreach focused on understanding the functioning and societal role of mountain forest ecosystems in the Pacific Northwest. We collaborate with a broad and diverse community of university and federal scientists, students, and land managers to support ecosystem science, education, natural resource management, and the arts and humanities. Research at the HJA encompasses the five core areas of LTER. Long-term observational and experimental studies include climate, hydrology, vegetation, carbon and nutrients, seed production, fish and salamanders, meadow plants and pollinators, and forest birds. Short-term experimental studies and modeling studies are designed to explore mechanisms for patterns observed in long-term studies. Our understanding of the ecosystem has developed over eight LTER cycles. LTER1-2 focused on establishing long-term measurements and research on fundamental ecosystem structure and processes. LTER3-7 were guided by a central question: How do land use, natural disturbances, and climate change affect three key ecosystem properties: carbon and nutrient dynamics, biodiversity, and hydrology? LTER cycles have also adopted themes: LTER3, process-based understanding of landscape dynamics; LTER4, effects of early succession and species attributes on ecosystem dynamics; LTER5, synchronous temporal behaviors and drivers of biogeochemical cycling in small watersheds; and LTER6, complex topography and its influence on ecosystem components. LTER7 focused on the causes and consequences of connectivity in our landscape. LTER8 research efforts focus on interactions, specifically: biotic modulation (how vegetation structure moderates ecosystem responses), legacy interactions (how past disturbance influences ecosystem responses), and species interactions (how relationships among species affect populations and communities), and interactions between science and values. The Andrews Forest LTER Program includes diverse education and outreach activities with multiple objectives and funding sources, including K-12, undergraduate, and graduate education, as well as a long-term program in arts and humanities. The program maintains strong connections and partnerships with forest managers, particularly with the Willamette National Forest and the USFS Pacific Northwest Research Station. The Andrews Forest LTER has a strong information management (IM) team that ensures that data collected as part of the Andrews Forest LTER are archived and openly available. The IM Team provides high-quality and well-documented data collections and plays key roles in the Andrews Forest LTER, the LTER Network, and the broader community of data users.Read Less

The H. J. Andrews Experimental Forest is situated in the western Cascade Range of Oregon in the 15,800-acre (6400-ha) drainage basin of Lookout Creek, a tributary of the Blue River and the McKenzie River. Elevation ranges from 1350 feet (410 m) to 5340 feet (1630 m). The HJA contains excellent examples of the region's conifer forests dominated by old-growth and second-growth Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla) at lower elevations, and Pacific silver fir (Abies amabilis), noble fir (Abies procera) and mountain hemlock (Tsuga mertensiana) at higher elevations. Mountain meadows are common in elevations above 4500 feet (1370 m). Rapidly flowing mountain streams carve out the landscape and create watersheds. The site is situated in the Pacific Northwest-North Pacific Ocean Bioclimatic region, which is dominated by cool, wet conditions derived partly from adjacency to the North Pacific Ocean. The wet-dry seasonal climate favors the development of massive, long-lived conifer trees. Most of the precipitation falls between November and April as rainfall (75%), but episodic snow accumulation can occur in winter at higher elevation sites. Peak stream flows can be flashy following winter rainstorms with seasonal low flow between July and September. When it was established in 1948, the HJA had not experienced any logging or road building activity. Before timber cutting began in 1950, about 65% of the HJA was old-growth forest (~500 years old) and the remaining forest area was mostly mature stands developed after wildfires in the mid-1800s to early 1900s. Clearcutting and shelterwood cuttings concentrated in the 1950s–70s, and green tree retention harvests in the 1980s and 1990s cover collectively about 30% of the HJA. These management treatments and post-harvest planting and thinning have created second-growth forests varying in composition, structure, biomass, and age. In 2020, the Holiday Farm wildfire burned 3% of the site, including three experimental watersheds: Watershed 1 (second-growth forest) and Watersheds 2 and 9 (old and mature forest). In 2023, the Lookout Fire burned roughly 70% of the site, in a mosaic of mixed burn severity.Read Less

The program has its roots at the H.J. Andrews Experimental Forest (HJA), established in 1948 by the U.S. Forest Service. In the 1950s and 1960s, Forest Service researchers focused on understanding the effects of timber and watershed management. In the late 1960s, university scientists became active at the site and research began on forest ecosystems, especially old-growth forests. The site became one of the first to receive an award from the National Science Foundation’s Long-term Ecological Research program in 1980. Long-term measurement programs began in experimental sites and watersheds with a focus on questions about climate, streamflow, water quality, vegetation succession, biogeochemical cycling, and effects of forest management. In our 70-year history, research has interacted within a continually evolving context of changes in the environment, in science, and in society. Research on old-growth forests and streams in the 1970s and 1980s contributed to the concept of the characteristics and function of old-growth forest, forest fragmentation, the river continuum concept, and the emerging field of landscape ecology. This research had a strong influence on the development of the Northwest Forest Plan—which represented a major shift in federal forest policy from conversion to conservation of old-growth forests. Work of the broader Andrews Forest Program (which includes the HJA Experimental Forest, LTER funded research, and other research programs) continues to help guide forest management and assessment of effects of environmental change.Read Less