Document


Title

Determining prescribed fire and fuel treatment compatibility with semi-desert grassland habitat rehabilitation for the critically endangered masked bobwhite quail (Colinus virginianus ridgwayi) - Final Report to the Joint Fire Science Program
Document Type: Report
Author(s): Steven E. Sesnie; Brett G. Dickson
Publication Year: 2018

Cataloging Information

Keyword(s):
  • Arizona
  • bobwhite quail
  • Buenos Aires National Wildlife Refuge
  • Colinus virginianus
  • habitat
  • SEM - structural equation modeling
  • vegetation dynamics
Region(s):
JFSP Project Number(s):
13-1-06-16
Record Maintained By:
Record Last Modified: August 5, 2019
FRAMES Record Number: 58389

Description

The Buenos Aires National Wildlife Refuge (BANWR) in southern Arizona was established in 1985 to provide habitat for threatened and endangered plant and animal species, with an emphasis on the critically endangered masked bobwhite quail (Colinus virginianus ridgwayi). Livestock grazing, fire regime disruption, pronounced drought, non-native grasses and altered arid-land hydrology since the late 1800s have each played a substantial role in transforming semi-desert grasslands. Since refuge establishment and grazing cessation, prescribed fire has featured prominently as a tool for achieving desired habitat conditions. We used a designed study and quantitative methods to assess vegetation structure and composition resulting from soil, topography, and climate factors in conjunction with management approaches used to encourage quail habitat. We randomly located vegetation plots (n = 239) within nine fire frequency and topographic strata to determine fire effects on habitat conditions important to masked bobwhites. We used field studies, multivariate and spatial data analysis to determine how fire and site biophysical conditions have led to present habitat conditions on BANWR. Structural equation models (SEM) and ordination plots revealed that soil texture and climate gradients across the study area were important to determining fire-effects on habitat. From SEM, we found that fire can potentially produce short-term benefits for quail such as greater forb and herbaceous plant cover. Increased forb cover may last as little 2 or 3 years on sites quickly retaken by the non-native perennial grass Eragrostis lehmanniana. Leguminous shrubs and subshrubs important to masked bobwhite as food resources were in low abundance throughout the study area. Woody plants (trees and shrubs) were significantly and negatively affected by frequent fire according to SEM. Subshrubs important for both cover and food resources were more abundant on plots (𝑥𝑥̅ = 5.2%±5.9 cover), but were not wide spread and had a weak, but significantly negative association with site fire history. These outcomes were likely due to Gutierrezia sarothrae, the most common subshrub found on plots, primarily used as cover by quail. Other common seed producing leguminous subshrubs important as winter food for quail such as Acacsia angustissima and Chamaecrista nictitans were associated with drainage areas, but often absent on plots and had low correlation with fire history variables. Plant interaction between E. lehmanniana and other native vegetation were critical to habitat conditions observed. We found that repeatedly burned sites were often those dominated by E. lehmanniana that showed higher fine-fuel concentrations, low plant diversity, and had significantly lower habitat suitability for masked bobwhite quail. A spatial model of masked bobwhite habitat suitability indicated that areas with greater suitability ranging from 0.50 to 0.68 were located on infrequently burned sites, a t the margin of fire management units. BANWR management units with the highest and most contiguously dense fine-fuel concentrations were those burned ≥4 time over a 30-year period. These areas were nearly devoid of suitable habitat for masked bobwhites and showed novel fuel conditions comprised of dense non-native grasses that can increase fire size and intensity. Non-linear models comparing fire history variables to masked bobwhite habitat suitability within BANWR management units showed a significantly negative relationship with fire frequency (F=14.8, P<0.001, r2 = 0.36) and significantly positive relationship with the number of years since last burn (F=14.6, P<0.001, r2 = 0.35). Conversely, locations with higher habitat suitability for quail tended to be on coarse textured soils with lower moisture holding capacity that were less suitable to E. lehmanniana. These sites were often associated with drainages protected from fire during prescribed fire activities that had few to no fires, likely because of low productivity and fine-fuel accumulation. Fire will undoubtedly continue to play a role on BANWR particularly in locations where fuel-bed structure and plant composition is dominated by dense non-native grasses. Efforts to improve habitat quality for masked bobwhite quail on the refuge should consider greater protection for critical habitat areas and active management to improve shrub cover (winter forage species), connectivity and diverse foraging opportunities among sites with better habitat quality. These areas may require sufficient recovery time from previous burns, ranging from 15 to 20 years depending on site environmental factors and interannual climate variability. However, recovery timeframes are uncertain because a majority of areas with higher predicted habitat suitability (≥0.50) showed no burn history in the last 30 years. Overall, habitat suitability was low on the refuge. Small-scale management experiments are greatly needed to better determine requisite treatments that can encourage masked bobwhite habitat recovery and suitable conditions for survival and reproduction. Adaptive management approaches could benefit many aspects of quail habitat rehabilitation and prescribe fire use on BANWR. Work summarized from this project provide a foundation from which various types of management activities might help to promote and improve habitat conditions for quail, but will require improved follow-up and monitoring to verify anticipated outcomes.

Online Link(s):
Link to this document (7 MB; pdf)
Citation:
Sesnie, Steven E.; Dickson, Brett G. 2018. Determining prescribed fire and fuel treatment compatibility with semi-desert grassland habitat rehabilitation for the critically endangered masked bobwhite quail (Colinus virginianus ridgwayi) - Final Report to the Joint Fire Science Program. JFSP Project No. 13-1-06-16. Albuquerque, NM: US Fish and Wildlife Service. 93 p.