© 1987 Heron Publishing—Victoria, Canada
Forest decline: modeling the effect of climate in tree rings
Edward R. Cook (1), Arthur H. Johnson (2) and Terence J. Blasing (3)
1. Tree-Ring Laboratory, Lamont-Doherty Geological Observatory, Palisades, NY 10964, USA / 2. Department of Landscape Architecture and Regional Planning and Department of Geology, University of Pennsylvania, Philadelphia,
PA 19104, USA / 3. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA /
Summary
Tree rings provide an historical record of forest growth that reflects changes with time in site factors including, competition,
tree and stand age, fire and other disturbances, and climate. Statistical methods can be used to factor out climatic influences
on radial growth to yield a climate response model that can indicate whether declines in forest productivity are related to
the modeled climatic variables or to other influences such as atmospheric pollutants. A general method, based on ordinary
least squares, is presented for creating climatic response models for forest decline studies. The crux of the method is model
verification, whereby the time-stability of the model is tested before it is used to forecast tree-ring variations during
a period of decline. Three studies are described that employ monthly mean temperatures to predict tree-ring indices in declining
red spruce (Picea rubens Sarg.) stands in the Appalachian Mountains of North America. The results indicate that, since 1960, red spruce trees at most
of the sites sampled have undergone a period of growth decline that is unrelated to changes in mean monthly temperature. However,
an association between annual ring width and unusual departures from the mean summer and winter temperatures during both present
and past periods of decline suggests that climatic effects are implicated to some degree in the current decline.
