Climate Variability and Ecosystem Response at the H. J. Andrews Long-Term Ecological Research Site

Abstract

The H. J. Andrews (AND) Long-Term Ecological Research (LTER) site represents the temperate coniferous forest of the Pacific Northwest (PNW) of the United States. The general climate of the area is highly dynamic, displaying variability at a variety of timescales ranging from daily to millennial. AND, and its surrounding region, is therefore an ideal site for examining some of the guiding questions of climate variability and ecosystem response addressed by this volume (see chapter 1). A legacy of more than 50 years of research at the site and its surrounding area ensures that several of the questions can be investigated in some depth. Here we organize our discussion within a timescale framework that is consistent with the structure of this volume. Thus, following a brief description of the general climate of the site, we discuss climate variability and ecosystem response at the daily, multidecadal, and century to millennial scale. This discussion for the PNW is supplemented in chapters 6 and 13 by a consideration of the quasi-quintennial scale and an additional ecosystem response at the decadal scale. Having described some of the climate variability and ecosystem response at the selected timescales, we will consider what this information can tell us regarding some of the guiding questions of this book. The questions that we specifically address include the following: What preexisting conditions affect the impact of the climatic event or episode? Is the climatic effect on the ecosystems direct or cascading? Does the system return to its original state? We also consider potential future climate change and its possible ecosystem effects. Located at latitude 44.2º N and longitude 122.2º W, the Andrews Forest is situated in the western Cascade Range of Oregon in the 6400-ha (15,800-acre) drainage basin of Lookout Creek, a tributary of the Blue River and the McKenzie River (figure 19.1). Elevation ranges from 410 m (1350 feet) to 1630 m (5340 feet). Broadly representative of the rugged mountainous landscape of the Pacific Northwest (PNW), the Andrews Forest contains excellent examples of the region’s conifer forests and associated wildlife and stream ecosystems. Lower elevation forests are dominated by Douglas-fir (Pseudotsuga menziesii), western hemlock (Tsuga heterophylla), and western red cedar (Thuja plicata).