Tree mortality and biomass loss in drought-affected forests of East Texas, USA

Mukti Ram Subedi, Weimin Xi, Christopher B. Edgar, Sandra Rideout-Hanzak, Ming Yan

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Changes in tree mortality due to severe drought can alter forest structure, composition, dynamics, ecosystem services, carbon fluxes, and energy interactions between the atmosphere and land surfaces. We utilized long-term (2000‒2017, 3 full inventory cycles) Forest Inventory and Analysis (FIA) data to examine tree mortality and biomass loss in drought-affected forests for East Texas, USA. Plots that experienced six or more years of droughts during those censuses were selected based on 12-month moderate drought severity [Standardized Precipitation Evaporation Index (SPEI) -1.0]. Plots that experienced other disturbances and inconsistent records were excluded from the analysis. In total, 222 plots were retained from nearly 4000 plots. Generalized nonlinear mixed models (GNMMs) were used to examine the changes in tree mortality and recruitment rates for selected plots. The results showed that tree mortality rates and biomass loss to mortality increased overall, and across tree sizes, dominant genera, height classes, and ecoregions. An average mortality rate of 5.89% year−1 during the study period could be incited by water stress created by the regional prolonged and episodic drought events. The overall plot and species-group level recruitment rates decreased during the study period. Forest mortality showed mixed results regarding basal area and forest density using all plots together and when analyzed the plots by stand origin and ecoregion. Higher mortality rates of smaller trees were detected and were likely compounded by density-dependent factors. Comparative analysis of drought-induced tree mortality using hydro-meteorological data along with drought severity and length gradient is suggested to better understand the effects of drought on tree mortality and biomass loss around and beyond East Texas in the southeastern United States.

Original languageEnglish (US)
Pages (from-to)67-80
Number of pages14
JournalJournal of Forestry Research
Issue number1
StatePublished - Mar 26 2020

Bibliographical note

Funding Information:
We are thankful to the Department of Physics and Geosciences, Texas A&M University-Kingsville, for providing access to the Geospatial Research Laboratory. We would like to thank the staff from Sam Houston, Sabine, Angelina, and Davy Crocket National Forests and Big Thicket National Preserve, especially Mr. Daniel P. Jauregui from Sam Houston National Forest, for his guidance during our field trip in 2014 and 2015. We would like to thank Drs. Eric Gustafson and Xiongqing Zhang for sharing their scripts.

Funding Information:
Project funding: This work was supported by partial financial support from a University Research Award, a STEP-HG Faculty Research Award, and Research Startup Funds from Texas A&M University-Kingsville to Dr. Xi.

Publisher Copyright:
© 2020, Northeast Forestry University.


  • Above-ground biomass
  • Biomass lost to mortality
  • Competition index
  • Drought index
  • East Texas
  • Endogenous factors
  • Generalized nonlinear mixed model
  • Standardized precipitation evaporation index (SPEI)


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