Human activities are changing patterns of disturbance across earth’s ecosystems. Fire is a type of disturbance that has become more frequent in some areas and suppressed in others. Surviving and regenerating native plants in post-fire ecosystems experience dramatic changes in resource availability and competition. How native plants recover from these changes determines the plant community and function of the ecosystem. The potential emergence of invasive grass fire cycles in the Mojave Desert provides an ideal study system for understanding how changing fire regimes affect post-disturbance native plant regeneration and resource competition.
The objective of this study is to examine the effects of fire on native shrub growth rates and reproduction over time. We conducted our study in the north eastern Mojave Desert near the Lytle Ranch Preserve. Samples were collected from five transect pairs along the burn boundaries of three independent 2005 wildfires. Five transects were located, not on the burn boundary, but further into the burned area. Our study focused on Larrea tridentata, a keystone species of the Mojave. Five L. tridentata were selected and tagged per transect. Fruit production was counted on each plant each June from 2015 to 2017. Branch samples were collected June 2017 from each of those same shrubs and age and size measurements were taken.
Results/Conclusions
Creosote branch growth rates along the burned edges were 2.6 times greater than those of unburned transects. Results for vertical growth rate followed a similar pattern with shrubs on burned transects growing 1.7 times more per year than shrubs on unburned transects. Creosote plants on burn edge transects produced on average 4.6 times more fruit per shrub than shrubs on unburned transects. Lastly, fruit density was on average 5.7 times greater for shrubs on burn edge transects versus shrubs on adjacent unburned transects. No significant differences were found for these measurements between shrubs from burn edge and burn interior transects.