DOI: 10.5061/dryad.jh9w0vtbk
title: Episodic occurrence of favorable weather constrains recovery of a cold desert shrubland after fire

description: 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 &lt; 0.18) and dominant
 subspecies (marginal R2 &lt; 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.
description: This dataset contains big sagebrush (Artemisia tridentata)
 establishment dates and shrub dimensions associated with JFSP Project #
 16-2-01-27. The data were collected in 12 sites from the SageSTEP and
 Underdown Canyon prescribed fire networks, which are located in sites
 co-dominated by sagebrush shrublands and pinyon-juniper woodlands in
 Nevada, Utah, Oregon, and California. Prescribed burn treatments took
 place between 2004 and 2008, and sites were sampled between 2015 and 2017.
 Clusters of sampling plots were randomly located within each prescribed
 fire site, and all big sagebrush individuals within the plots were
 measured (canopy diameters and height) and then destructively sampled. A
 stem sample was collected from each sagebrush individual that included the
 root collar, and stem samples were sectioned at to the lowest appearance
 of the pith and progressively sanded. Stem samples were examined under the
 microscope, and the establishment date was determined based on the count
 of annual rings. Stem diameters were measured with calipers on the
 processed stem samples.
description: Excel file with descriptions of each of the data fields is
 available as a separate file.
 "Urza_etal_ARTR_dendro_README.xlsx"