Non-timber forest product harvest in variable environments: Modeling the effect of harvesting as a stochastic sequence

Orou G. Gaoue, Carol C. Horvitz, Tamara Ticktin

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


With increasing reports of overexploitation of wild plants for timber and non-timber forest products, there has been an increase in the number of studies investigating the effect of harvest on the dynamics of harvested populations. However, most studies have failed to account for temporal and spatial variability in the ecological conditions in which these species occur, as well as variability in the patterns of harvest intensity. In reality, local harvesters harvest at variable rather than fixed intensity over time. Here we used Markov chains to investigate how different patterns of harvesting intensity (summarized as return time to high harvest) affected the stochastic population growth rate (λ s) and its elasticity to perturbation of means and variances of vital rates. We studied the effect of bark and foliage harvest from African mahogany Khaya senegalensis in two contrasting ecological regions in Benin. Khaya populations declined regardless of time between harvests of high intensity. Moreover, λ s increased with decreasing harvesting pressure in the dry region but, surprisingly, declined in the moist region toward λ s = 0.956. The stochastic elasticity was dominated by the stasis of juveniles and adults. The declining growth rate with decreasing harvest pressure in the moist region was mainly driven by the declining mean survival rates of juveniles and adults. Our results suggest that modeling the temporal variability of harvest intensity as a Markov chain better mimics local practices and provides insights that are missed when temporal variability in harvest intensity is modeled as independent over time and drawn from a fixed distribution.

Original languageEnglish (US)
Pages (from-to)1604-1616
Number of pages13
JournalEcological Applications
Issue number5
StatePublished - Jul 2011


  • African mahogany
  • Benin, West Africa
  • Contrasting ecological conditions
  • Effect of NTFP harvest
  • Environment-specific elasticity
  • Harvest return time
  • Khaya senegalensis
  • Markov chain
  • Matrix models
  • Stochastic elasticity
  • Tropical trees

ASJC Scopus subject areas

  • Ecology


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