Profiling overstory survival trends following varying thinning and burning disturbance regimes in a mixed pine-hardwood forest in the US South


Prescribed burning as a silvicultural tool may be effective for achieving various management objectives, yet some
practitioners have concerns about inadvertently increasing overstory tree mortality. Using extensive data from a
long-term, ongoing study in northcentral Alabama, USA, that systematically applies a variety of thinning and
prescribed burning disturbances on mixed pine-hardwood stands, we assess survival trends for different groups of
trees. The primary research question is whether more frequent prescribed burns adversely affects overstory
survival versus infrequent or no burns; secondary questions explore whether overstory survival trends differ
based on thinning level, species group, or size class. Interest is in broad groups of trees, not individual tree
survival or mortality; consequently, survival analysis methods are used, including nonparametric Kaplan-Meier
(KM) techniques for examining single grouping factors, and parametric accelerated failure time models for
analyzing simultaneous effects of multiple covariates. Leveraging relatively recent methodological advances, the
statistical techniques are adjusted for interval censored data. KM survival curves showed that more frequent
prescribed fires did not result in differing survival trends. Also, trees in unthinned stands had the lowest 14-year
survival compared to thinned stands, oaks had the highest survival compared to pines and the others species
group, and the smallest size class of overstory trees had the lowest survival. These results support managing
transitional mixed pine-hardwoods using thinning and multiple prescribed fires to restore specific species
composition and structure.

  • Citation: Craycroft, John; Schweitzer, Callie. 2023. Profiling overstory survival trends following varying thinning and burning disturbance regimes in a mixed pine-hardwood forest in the US South. Forest Ecology and Management. 531: 120796-.
  • Keywords: prescribed fire, tree mortality, silviculture treatments, mixedwoods, survival analysis, interval censoring
  • Posted Date: February 1, 2023
  • Modified Date: February 2, 2023
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