Skip to main content
Dryad

Episodic occurrence of favorable weather constrains recovery of a cold desert shrubland after fire

Data files

May 17, 2021 version files 112.25 KB

Abstract

1. Key to the long-term resilience of dryland ecosystems is the recovery of foundation plant species following disturbance. In ecosystems with high interannual weather variability, understanding the influence of short-term environmental conditions on establishment of foundation species is essential for identifying vulnerable landscapes and developing restoration strategies. We asked how annual environmental conditions affect post-fire establishment of Artemisia tridentata, a shrub species that dominates landscapes across much of the western United States, and evaluated the influence of episodic establishment on population recovery. 2. We collected A. tridentata stem samples from 33 plots in 12 prescribed fire sites that burned 8-11 years before sampling. We determined individual establishment years using annual growth rings. We measured seasonal soil environmental conditions at the study sites and asked if these conditions predicted annual establishment density. We then evaluated whether establishment patterns could be predicted by site-level climate or dominant subspecies. Finally, we tested the effect of the magnitude and frequency of post-fire establishment episodes on long-term population recovery. 3. Annual post-fire recruitment of A. tridentata was driven by the episodic availability of spring soil moisture. Annual establishment was highest with wetter spring soils (relative influence [RI] = 19.4%) and later seasonal dry-down (RI = 11.8%) in the year of establishment. Establishment density declined greatly four to five years after fire (RI = 17.1%). Post-fire establishment patterns were poorly predicted by site-level mean climate (marginal R2 < 0.18) and dominant subspecies (marginal R2 < 0.43). 4. Population recovery reflected the magnitude, but not the frequency, of early post-fire establishment pulses. Post-fire A. tridentata density and cover (8-11 years after fire) were more strongly related to the magnitude of the largest establishment pulse than to establishment frequency, suggesting that population recovery may occur with a single favorable establishment year. 5. Synthesis and applications. This study demonstrates the importance of episodic recruitment for long-term plant population dynamics following disturbance and indicates opportunities for improving restoration outcomes. Fire management strategies that retain unburned patches will increase seed availability during the post-fire establishment window, and repeated seeding coupled with seasonal weather forecasts can improve establishment in high-priority areas.