Format

Send to

Choose Destination
Ecol Appl. 2016 Oct;26(7):2311-2322. doi: 10.1002/eap.1371. Epub 2016 Sep 23.

Spreaders, igniters, and burning shrubs: plant flammability explains novel fire dynamics in grass-invaded deserts.

Author information

1
Laboratorio de Biometria, Departamento de Ciencias Forestales, Universidad de La Frontera, Casilla 54-D, Temuco, Chile. andres.fuentes@ufrontera.cl.
2
Department of Ecology, Evolution and Organismal Biology, Iowa State University, 251 Bessey Hall, Ames, Iowa, 50011, USA.
3
Department of Biological Sciences, Rutgers State University of New Jersey, 195 University Avenue, Newark, New Jersey, 07102, USA.

Abstract

Novel fire regimes are an important cause and consequence of global environmental change that involve interactions among biotic, climatic, and human components of ecosystems. Plant flammability is key to these interactions, yet few studies directly measure flammability or consider how multiple species with different flammabilities interact to produce novel fire regimes. Deserts of the southwestern United States are an ideal system for exploring how novel fire regimes can emerge when fire-promoting species invade ecosystems comprised of species that did not evolve with fire. In these deserts, exotic annual grasses provide fuel continuity across landscapes that did not historically burn. These fires often ignite a keystone desert shrub, the fire-intolerant creosote bush, Larrea tridentata (DC.) Coville. Ignition of Larrea is likely catalyzed by fuels produced by native plants that grow beneath the shrubs. We hypothesize that invasive and native species exhibit distinct flammability characteristics that in combination determine spatial patterns of fire spread and intensity. We measured flammability metrics of Larrea, two invasive grasses, Schismus arabicus and Bromus madritensis, and two native plants, the sub-shrub Ambrosia dumosa and the annual herb Amsinckia menziesii. Results of laboratory experiments show that the grasses carry fire quickly (1.32 cm/s), but burn for short duration (0.5 min) at low temperatures. In contrast, native plants spread fire slowly (0.12 cm/s), but burn up to eight times longer (4 min) and produced hotter fires. Additional experiments on the ignition requirements of Larrea suggest that native plants burn with sufficient temperature and duration to ignite dead Larrea branches (time to ignition, 2 min; temperature at ignition 692°C). Once burning, these dead branches ignite living branches in the upper portions of the shrub. Our study provides support for a conceptual model in which exotic grasses are "spreaders" of fire and native plants growing beneath shrubs are "igniters" of dead Larrea branches. Once burning, flames produced by dead branches engulf the entire shrub, resulting in locally intense fires without historical precedent in this system. We suggest that fire models and conservation-focused management could be improved by incorporating the distinct flammability characteristics and spatial distributions of spreaders, igniters, and keystone shrubs.

KEYWORDS:

Mojave desert, USA; Sonoran desert, USA; biological invasions; fire behavior; fire modeling; fuel treatments; native annuals; non-fire adapted systems; prescribed fire; species interactions

PMID:
27755715
DOI:
10.1002/eap.1371
[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Wiley
Loading ...
Support Center