First-Order Fire Effects on Herbs and Shrubs: Present Knowledge and Process Modeling Needs

Abstract

Herbaceous plants and shrubs have received little attention in terms of fire effects modeling despite their critical role in ecosystem integrity and resilience after wildfires and prescribed burns. In this paper, we summarize current knowledge of direct effects of fire on herb and shrub (including cacti) vegetative tissues and seed banks, propose key components for process-based modeling, and outline research needs. Most herbs and shrubs are likely to be killed or top-killed even in low intensity surface fires. Therefore, modeling efforts should focus on mortality of protected above and below ground meristematic tissue and seeds as well as the effects on seed germination. Further development of an organic and mineral soil heating model capable of describing heating patterns under a range of flaming and smoldering fire behaviors, validated heat transfer models for protected plant structures, standardized descriptions of tissue heat tolerance for a wider range of species, and a better understanding of the effects of soil heating on seed banks are required. The combination of these components would result in a comprehensive, process-based model predicting immediate herb, shrub, and seed mortality and post-fire responses. It would permit quantitative description of fire severity and a more accurate prediction of post-fire ecosystem recovery.