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

Citation

Urza, Alexandra et al. (2021), Episodic occurrence of favorable weather constrains recovery of a cold desert shrubland after fire, Dryad, Dataset, https://doi.org/10.5061/dryad.jh9w0vtbk

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.

Methods

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.

Usage Notes

Excel file with descriptions of each of the data fields is available as a separate file. "Urza_etal_ARTR_dendro_README.xlsx"

Funding

Joint Fire Science Program, Award: 16-2-01-27