Why Permanent Plots?

The aim of the Pacific Northwest Permanent Sample Plot Program (PNW-PSP) is to study and quantify the long-term dynamics of forest vegetation. We manage more than 150 plot installations across a diversity of forest types in Oregon and Washington. These include coastal forests of spruce and hemlock, Douglas-fir-dominated forests of the western Cascades, higher-elevation forests of mountain hemlock and silver fir, as well as ponderosa pine forests in Central Oregon (view map of study sites). Plots are situated in six national forests, four experimental forests (HJ Andrews, Wind River, Cascade Head, Pringle Falls), fourteen research natural areas (RNA’s), two national parks (Mt. Rainier, Olympic) and one national monument (Mount St. Helens).

The PNW-PSP Program is historically significant, with data records spanning decades to more than 100 years (figure below). Long-term observational data such as these are essential to understanding the fundamental processes of tree growth, mortality, regeneration and plant succession. Indeed, PNW-PSP data have enhanced our understanding of a broad range of topics relevant to forest management and ecology, including: old-growth forest structure, timber production, carbon sequestration, wildlife habitat, biodiversity, response to disturbance, and validation of remotely sensed data.  Find out more about these contributions to science and forest management on our publications page.

PNW-PSP is coordinated through Oregon State University's College of Forestry, in partnership with scientists from other universities and agencies.

The permanent plot network encompasses a broad spectrum of successional
(seral) stages, from regenerating plantations to old growth. The data record
stretches from 10 to more than 100 years.