Skip to Main Content
U.S. Forest Service
Caring for the land and serving people

United States Department of Agriculture

Home > Search > Publication Information

  1. Share via EmailShare on FacebookShare on LinkedInShare on Twitter
    Dislike this pubLike this pub
    Author(s): David M. BellWarren B. Cohen; Matthew Reilly; Zhiqiang Yang
    Date: 2018
    Source: Ecosphere. 9(6): e02195-.
    Publication Series: Scientific Journal (JRNL)
    Station: Pacific Northwest Research Station
    PDF: Download Publication  (5.0 MB)


    Remote sensing studies indicate that slow and subtle degradation of forest canopies, or forest canopy declines, has increased in extent during recent decades, possibly due to hotter and drier droughts. However, it is difficult to collect consistent, high-quality time series of forest canopy decline occurrence observations needed for examining multi-year drought contributions to forest canopy decline at an annual scale. In this research, we leveraged a tool for visual interpretation of annual Landsat satellite imagery (TimeSync) and a hierarchical Bayesian time series modeling approach (stochastic antecedent modeling, SAM) in five forest type groups located in the western United States to assess (1) what seasonal and interannual patterns in vapor pressure deficit (VPD) and precipitation preceded forest canopy decline events, (2) how drought effects on forest canopy decline events differed by forest type group, and (3) whether or not drought effects on forest canopy decline events were uniform within forest type groups. We examined observations of forest canopy decline over three decades (1985–2013) at 126 plots where we collected annual TimeSync observations. Stochastic antecedent modeling indicated that January–March VPD and July–September precipitation anomalies for the current year and 1–3 yr in the past contributed to defining drought conditions in relation to forest canopy decline dynamics. The probability of forest canopy decline decreased with summer precipitation for all forest type groups and increased with winter VPD for the warmest and the coldest forest type groups. However, the magnitude and direction of forest canopy decline sensitivity to drought varied substantially within forest type groups. The ubiquitous, but not uniform, effects of drought on forest canopy decline dynamics implied that local biotic (e.g., forest structure and composition, tree genetics) and abiotic (e.g., topography and soils) factors act to mediate effects of drought on forest change. The integration of the TimeSync satellite image interpretation tool with SAM provides a promising approach to link ecological understanding of tree drought responses to forest and landscape responses at regional and continental scales.

    Publication Notes

    • Visit PNW's Publication Request Page to request a hard copy of this publication.
    • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.


    Bell, David M.; Cohen, Warren B.; Reilly, Matthew; Yang, Zhiqiang. 2018. Visual interpretation and time series modeling of Landsat imagery highlight drought's role in forest canopy declines. Ecosphere. 9(6): e02195-.


    Google Scholar


    Drought, forest canopy decline, Landsat, Special Feature: Emerging Technologies in Ecology, stochastic antecedent modeling, TimeSync, western United States.

    Related Search

    XML: View XML
Show More
Show Fewer
Jump to Top of Page