Peak fire temperature and effects on annual plants in the Mojave desert
Brooks ML. 2002. Peak fire temperature and effects on annual plants in the Mojave desert. Ecological Applications. 12(4):1088-1102
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 microhabitats and distances from the soil surface, and between spring and summer. Microhabitats ranged from high amounts of fuel beneath creosote bust (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 with 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 amoung 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 increase 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 accout 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 microhabit affinites, 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.
- Type
- Journal Article
- Authors
- Brooks, Mathew
- Units
- SODN
- Keywords
- California, FIRE, Invasive Plants, Land Management, Mojave Desert, Nitrogen, postfire succession, red brome, Soil nutrients, Water repellency