Peak Fire Temperatures and Effects on Annual Plants in the Mojave Desert

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecological Applications. Abstract. Very little is known about the behavior and effects of fire in the Mojave Desert, because fire was historically uncommon. However, fire has become more frequent since the 1970s with increased dominance of the invasive annual grasses Bromus rubens and Schismus spp., and land managers are concerned about its ecological effect. In this paper, I describe patterns of peak fire temperature and their effect on annual plants in creosote bush scrub vegetation of the Mojave Desert. Temperatures were monitored among microhabitats and distances from the soil surface, and between spring and summer. Microhabitats ranged from high amounts of fuel beneath creosote bush (Larrea tridentata) canopies, to intermediate amounts at the canopy drip line, to low amounts in the interspaces between them. Distances from the soil surface were within the vertical range where most annual plant seeds occur (-2, 0, 5, and 10 cm). I also compare temperature patterns with postfire changes in soil properties and annual plant biomass and species richness to infer potential mechanisms by which fires affect annual plants.Peak fire temperatures were most affected by the microhabitat fuel gradient, and the effects of fire on annual plants varied among microhabitats. Beneath creosote bushes, lethal fire temperatures for annual plant seeds occurred above-and belowground, resulting in four postfire years of reduced annual plant biomass and species richness due most likely to seed mortality, especially of Bromus rubens and native forbs. At the canopy drip line, lethal fire temperatures occurred only aboveground, reducing annual plant biomass for 1 yr and species richness for 2 yr, and increasing biomass of Schismus sp., the alien forb Erodium cicutarium, and native annuals after 3 yr. Negligible changes were caused by fire in interspaces or between spring and summer.Fire effects models for creosote bush scrub vegetation must account for patterns of peak fire temperature along the shrub-intershrub gradient. The responses of annual plants to this gradient vary depending on the species composition of the seedling cohort, their microhabitat affinities, and their respective phenologic stages at the time of burning. Fire can temporarily reduce seed densities of Bromus rubens, but dominance of Schismus sp. may quickly increase above prefire levels.wilderness areas (Brooks, in press; BLM-CDD records). Fire is now considered one of the primary threats to the conservation of native plants and animals and the maintenance of ecosystem integrity in the Mojave Desert (Lovich and Bainbridge 1999; Brooks, ...

Post‐Fire Control of Invasive Plants Promotes Native Recovery in a Burned Desert Shrubland

“…Bromus madritensis abundance was dramatically reduced by the fire, but Schismus spp. and Erodium cicutarium benefited, similar to other studies (Minnich & Dezzani 1998; Brooks 2002).…”

Disturbance and Plant Succession in the Mojave and Sonoran Deserts of the American Southwest

“…However, some trends appeared from the collective results of individual studies. First, several studies reported a strong temporal influence (linked to precipitation) on the reestablishment of annual plants, where rainfall amounts in a given year could overwhelm any effects of disturbance (e.g., [53,60,76]). In some years of low rainfall virtually no annuals may be recorded, whereas in moist years, biomass and cover may increase several orders of magnitude.…”

“…In some years of low rainfall virtually no annuals may be recorded, whereas in moist years, biomass and cover may increase several orders of magnitude. Second, Brooks [60] and Cave and Patten [72] highlighted the effects of microsite (e.g., below shrubs versus in interspaces between shrubs) on the distribution and abundance of annual plants in both disturbed and undisturbed areas. Overall, annual plants were more abundant below shrubs in both areas, but some annual species showed contrasting patterns.…”

“…For example, the non-native grass red brome has often decreased the first few years following disturbance in permanent plot studies [53,60,72]. Redstem stork's bill ( Erodium cicutarium ), in contrast, has increased rapidly [53,57,60,65,73].…”

“…For example, the non-native grass red brome has often decreased the first few years following disturbance in permanent plot studies [53,60,72]. Redstem stork's bill ( Erodium cicutarium ), in contrast, has increased rapidly [53,57,60,65,73]. Native annuals reported to colonize disturbed areas include desert Indianwheat ( Plantago ovata ) following fire and land clearing in both the Mojave and Sonoran Deserts [64,72,76], whitestem blazingstar ( Mentzelia albicaulis ) after nuclear detonation tests in the northern Mojave Desert [42], flatcrown buckwheat ( Eriogonum deflexum ) on abandoned roads and cleared areas in the Mojave Desert [57,64], and species such as cryptantha ( Cryptantha spp.)…”