Population-wide changes in pinyon-juniper woodlands caused by drought in the American Southwest: Effects on structure, composition, and distribution

Abstract

A complex of drought, insects, and disease caused widespread mortality in the pinyon-juniper forest types of the American Southwest in recent years. Data from 14,929 plots spanning 25 years and representing over 25 million hectares were analyzed to characterize effects of drought-related mortality on the structure, composition, and distribution of pinyon and juniper species throughout their ranges. Pinus edulis experienced higher rates of mortality since 2003 than at any time between 1981 and 2002. Most Juniperus species experienced very low rates of mortality under normal conditions, and showed a small increase in mortality during the recent drought event. Trees affected by drought tend to be lower in elevation than the general population, and smaller trees appear to have experienced a higher proportion of mortality than larger trees. However, there is no evidence of elevational or geographic range contraction. This analysis quantifies landscape-level changes resulting from human, biological, and climatic influences.

Citation

Shaw, John D. 2006. Population-wide changes in pinyon-juniper woodlands caused by drought in the American Southwest: Effects on structure, composition, and distribution. In: Lafortezza, R.; Sanesi, G. (eds). Patterns and processes in forest landscapes. Consequences of Human Management. Proceedings of the 4th Meeting of IUFRO Working Party 8.01.03, Sept. 26-29, 2006, Locorotondo, Bari, Italy. p. 117-124