All 7 of the Andrews Forest plots are situated within the H. J. Andrews Experimental Forest (HJA) long term ecological research site (LTER). The 6,400-ha HJA encompasses an entire watershed and spans an elevational gradient from 410 m to 1,590 m, characterized by differences in mean annual temperature (range =7.4°C to 10.3°C) and precipitation (range =2,040 mm/yr to 2,354 mm/yr). Long-term meteorological stations are situated near the bottom (436 m) and top (1,268 m) of the HJA and within several of the forest plots, providing long-term climate data for our plots. These long-term data show that low-elevation valleys generally have higher mean-spring temperatures and greater relative humidity throughout most of the year than higher elevations. At lower elevations, more moderate temperatures and adequate moisture provide a long growing season for evergreen plant species, even during the winter. At higher elevations, freezing temperatures, persistent snowpack, a short pulse of water from snowmelt in spring/early summer, dry summers, and freezing temperatures throughout the wet season both shorten the growing season and likely influence decomposition rates and nutrient availability.

The Andrews Forest is one of 28 NSF Long Term Ecological Research (LTER) field sites. LTER’s mission is to provide the scientific community, policy makers, and society with the knowledge and predictive understanding necessary to conserve, protect, and manage the nation’s ecosystems, their biodiversity, and the services they provide. The LTER Network was founded in 1980 by the National Science Foundation with the recognition that long-term research could help unravel the principles and processes of ecological science, which frequently involves long-lived species, legacy influences, and rare events. In fact, the Andrews Forest was one of the first LTER sites established in 1980, with commensurate long time-series of observational and experimental data. As policymakers and resource managers strive to incorporate reliable science in their decision making, the LTER Network works to generate and share useful and usable information.