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Keywords:

  • Aspect;
  • Bryophytes;
  • Cryptogams;
  • Early-seral;
  • Fire severity;
  • Initial floristics;
  • Managed forests;
  • Mixed conifer forest;
  • Mixed severity fire;
  • Pacific Northwest;
  • Plant community;
  • Relay floristics;
  • Succession

Abstract

Question: How does vegetation develop during the initial period following severe wildfire in managed forests?

Location: Southwestern Oregon, USA.

Methods: In severely burned plantations, dynamics of (1) shrub, herbaceous, and cryptogam richness; (2) cover; (3) topographic, overstory, and site influences were characterized on two contrasting aspects 2 to 4 years following fire. Analysis of variance was used to examine change in structural layer richness and cover over time. Non-metric multidimensional scaling, multi-response permutation procedure, and indicator species analysis were used to evaluate changes in community composition over time.

Results: Vegetation established rapidly following wildfire in burned plantations, following an initial floristics model of succession among structural layers. Succession within structural layers followed a combination of initial and relay floristic models. Succession occurred simultaneously within and among structural layers following wildfire, but at different rates and with different drivers. Stochastic (fire severity and site history) and deterministic (species life history traits, topography, and pre-disturbance plant community) factors determined starting points of succession. Multiple successional trajectories were evident in early succession.

Conclusions: Mixed conifer forests are resilient to interacting effects of natural and human-caused disturbances. Predicting the development of vegetation communities following disturbances requires an understanding of the various successional components, such as succession among and within structural layers, and the fire regime. Succession among and within structural layers can follow different successional models and trajectories, occurs at different rates, and is affected by multiple interacting factors.