Forest Drought Response Index (ForDRI): A New Combined Model to Monitor Forest Drought in the Eastern United States

Authors

Tsegaye Tadesse, University of Nebraska - LincolnFollow
David Y. Hollinger, Northern Research Station
Yared A. Bayissa, University of Nebraska - Lincoln
Mark Svoboda, University of Nebraska - LincolnFollow
Brian Fuchs, University of Nebraska - LincolnFollow
Beichen Zhang, University of Nebraska - LincolnFollow
Getachew Demissie, University of Nebraska - Lincoln
Brian D. Wardlow, University of Nebraska - LincolnFollow
Gil Bohrer, The Ohio State University
Kenneth L. Clark, Northern Research Station
Ankur R. Desai, University of Wisconsin-Madison
Lianhong Gu, Oak Ridge National Laboratory
Asko Noormets, Texas A & M University - College Station
Kimberly A. Novick, Indiana University
Andrew D. Richardson, Northern Arizona University

ORCID IDs

Tsegaye Tadesse

David Y. Hollinger

Mark Svoboda

Brian D. Wardlow

Gil Bohrer

Kenneth L. Clark

Ankur R. Desai

Asko Noormets

Document Type

Article

Date of this Version

11-3-2020

Citation

Remote Sens. 2020, 12, 3605; doi:10.3390/rs12213605

Comments

CC-BY

Abstract

Monitoring drought impacts in forest ecosystems is a complex process because forest ecosystems are composed of different species with heterogeneous structural compositions. Even though forest drought status is a key control on the carbon cycle, very few indices exist to monitor and predict forest drought stress. The Forest Drought Indicator (ForDRI) is a new monitoring tool developed by the National Drought Mitigation Center (NDMC) to identify forest drought stress. ForDRI integrates 12 types of data, including satellite, climate, evaporative demand, ground water, and soil moisture, into a single hybrid index to estimate tree stress. The model uses Principal Component Analysis (PCA) to determine the contribution of each input variable based on its covariance in the historical records (2003–2017). A 15-year time series of 780 ForDRI maps at a weekly interval were produced. The ForDRI values at a 12.5km spatial resolution were compared with normalized weekly Bowen ratio data, a biophysically based indicator of stress, from nine AmeriFlux sites. There were strong and significant correlations between Bowen ratio data and ForDRI at sites that had experienced intense drought. In addition, tree ring annual increment data at eight sites in four eastern U.S. national parks were compared with ForDRI values at the corresponding sites. The correlation between ForDRI and tree ring increments at the selected eight sites during the summer season ranged between 0.46 and 0.75. Generally, the correlation between the ForDRI and normalized Bowen ratio or tree ring increment are reasonably good and indicate the usefulness of the ForDRI model for estimating drought stress and providing decision support on forest drought management.