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Occupancy and abundance of predator and prey: Implications of the fire-cheatgrass cycle in sagebrush ecosystems

DOI:10.1002/ecs2.1307
Authors:
Joseph D Holbrook at University of Wyoming
Joseph D Holbrook
Robert S. Arkle at United States Geological Survey
Robert S. Arkle
Janet L. Rachlow at University of Idaho
Janet L. Rachlow
Kerri T. Vierling at University of Idaho
Kerri T. Vierling
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Abstract and Figures

Sagebrush (Artemisia tridentata) ecosystems are declining due to biological invasions and changes in fire regimes. Understanding how ecosystem changes influence functionally important animals such as ecosystem engineers is essential to conserve ecological functions. American badgers (Taxidea tax-us) are an apex predator and ecosystem engineer in that they redistribute large amounts of soil within sagebrush ecosystems. Piute ground squirrels (Urocitellus mollis) are also an ecosystem engineer as well as an essential prey resource for many predators, including badgers. Our research objective was to evaluate the relative importance of biological invasions and fire, abiotic factors, and biotic factors on badgers and ground squirrels. We sampled 163 1-ha plots during April-June across a gradient of burn histories within a 1962 km 2 study area in southern Idaho, USA. At each plot, we characterized occupancy of ground squirrels and badgers and relative abundance of ground squirrels. Additionally, we characterized soil texture, climate, connectivity and dispersal potential, fire frequency, grazing, and cover of many plant species including a highly invasive exotic annual grass (cheatgrass; Bromus tectorum). We used an integrated approach to evaluate competing hypotheses concerning factors influencing occupancy and abundance. Results suggested that occupancy of ground squirrels was positively associated with long-term precipitation, dispersal potential, and fine-grained soil. Abundance of ground squirrels was positively associated with fine-grained soil, but negatively associated with cheatgrass, fire frequency, agriculture, and shrub cover. Badger occupancy was positively associated with ground squirrel occupancy and agriculture, which indicated affinity to prey. Our results provide insight into the relative influence of abiotic and biotic factors on predator and prey, and highlight how effects change across different population parameters. Our research suggests that widespread environmental change within sagebrush ecosystems, especially the fire-cheatgrass cycle (e.g., invasion of cheatgrass and increased fire frequency) and human land disturbances, are directly and indirectly influencing ground squirrels and badgers. However, we also found evidence that efforts to mitigate these stressors, for example, establishing bunchgrasses postfire, may provide targeted conservation strategies that promote these species and thus preserve the burrowing and trophic functions they provide.
Hypothesized strength of effect across biotic and abiotic themes for occupancy of Piute ground squirrels (Urocitellus mollis) and American badgers (Taxidea taxus) and abundance of ground squirrels. Abiotic themes include soil, climate, and disturbance (i.e., fire), whereas biotic themes include landscape, dispersal, disturbance (i.e., grazing), predation, prey, and forage. Asterisks indicate an ecosystem stressor (i.e., biological invasions and fire) is embedded within the theme. See Appendix S2: Tables S1–S3 for specific variables within biotic and abiotic themes.
Hypothesized strength of effect across biotic and abiotic themes for occupancy of Piute ground squirrels (Urocitellus mollis) and American badgers (Taxidea taxus) and abundance of ground squirrels. Abiotic themes include soil, climate, and disturbance (i.e., fire), whereas biotic themes include landscape, dispersal, disturbance (i.e., grazing), predation, prey, and forage. Asterisks indicate an ecosystem stressor (i.e., biological invasions and fire) is embedded within the theme. See Appendix S2: Tables S1–S3 for specific variables within biotic and abiotic themes.
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(a) Location of Morley Nelson Snake River Birds of Prey National Conservation Area (i.e., study area) in southwestern Idaho, USA. (b) Distribution of 1-ha plots (n = 163) that were sampled for Piute ground squirrels (Urocitellus mollis) and American badgers (Taxidea taxus). (c) Photograph of a badger on one of our 1-ha plots (taken by J. Holbrook).
(a) Location of Morley Nelson Snake River Birds of Prey National Conservation Area (i.e., study area) in southwestern Idaho, USA. (b) Distribution of 1-ha plots (n = 163) that were sampled for Piute ground squirrels (Urocitellus mollis) and American badgers (Taxidea taxus). (c) Photograph of a badger on one of our 1-ha plots (taken by J. Holbrook).
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Standardized parameter estimates (±90% credible intervals) describing the effect of explanatory variables (x-axis) on occupancy of Piute ground squirrels (Urocitellus mollis). Data were collected on the Morley Nelson Snake River Birds of Prey National Conservation Area in southern Idaho, USA. Variable descriptions are as follows: precipitation – mean annual precipitation from 1979 to 2008, DI – dispersal index (i.e., number of burrows at the nearest sampled 1-ha plot/distance to the plot), and soil texture – % surface soil passing through a #4 sieve.
Standardized parameter estimates (±90% credible intervals) describing the effect of explanatory variables (x-axis) on occupancy of Piute ground squirrels (Urocitellus mollis). Data were collected on the Morley Nelson Snake River Birds of Prey National Conservation Area in southern Idaho, USA. Variable descriptions are as follows: precipitation – mean annual precipitation from 1979 to 2008, DI – dispersal index (i.e., number of burrows at the nearest sampled 1-ha plot/distance to the plot), and soil texture – % surface soil passing through a #4 sieve.
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Standardized parameter estimates (±90% confidence intervals) describing the effect of explanatory variables (x-axis) on occupancy of American badgers (Taxidea taxus). If a variable does not have a parameter estimate labeled top model it was not included. Data were collected on the Morley Nelson Snake River Birds of Prey National Conservation Area in southern Idaho, USA. Variable descriptions are as follows: firefreq – number of times the area burned from 1957 to 2013, GSOcc – occupancy of Piute ground squirrels (Urocitellus mollis) at plot-level, human – % human disturbance within a 2.4 km 2 area, and soil texture – % surface soil passing through a #4 sieve.
Standardized parameter estimates (±90% confidence intervals) describing the effect of explanatory variables (x-axis) on occupancy of American badgers (Taxidea taxus). If a variable does not have a parameter estimate labeled top model it was not included. Data were collected on the Morley Nelson Snake River Birds of Prey National Conservation Area in southern Idaho, USA. Variable descriptions are as follows: firefreq – number of times the area burned from 1957 to 2013, GSOcc – occupancy of Piute ground squirrels (Urocitellus mollis) at plot-level, human – % human disturbance within a 2.4 km 2 area, and soil texture – % surface soil passing through a #4 sieve.
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Standardized parameter estimates (±90% confidence intervals) describing the effect of explanatory variables (x-axis) on relative abundance of Piute ground squirrels (Urocitellus mollis). If a variable does not have a parameter estimate labeled top model it was not included. Data were collected on the Morley Nelson Snake River Birds of Prey National Conservation Area in southern Idaho, USA. Variable descriptions are as follows: BRTE – plot-level % cover of cheatgrass (Bromus tectorum), precipitation – mean annual precipitation from 1979 to 2008, DI – dispersal index (i.e., number of burrows at the nearest sampled 1-ha plot/distance to the plot), firefreq – number of times the area burned from 1957 to 2013, human – % human disturbance within a 0.79 km2 area, season – binary variable to account for within season decline in active burrows (Van Horne et al. 1997b), shrub – plot-level % cover of shrub functional group, shrubland – % shrubland within a 0.79 km2 area, and soil texture – % surface soil passing through a #4 sieve.
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Standardized parameter estimates (±90% confidence intervals) describing the effect of explanatory variables (x-axis) on relative abundance of Piute ground squirrels (Urocitellus mollis). If a variable does not have a parameter estimate labeled top model it was not included. Data were collected on the Morley Nelson Snake River Birds of Prey National Conservation Area in southern Idaho, USA. Variable descriptions are as follows: BRTE – plot-level % cover of cheatgrass (Bromus tectorum), precipitation – mean annual precipitation from 1979 to 2008, DI – dispersal index (i.e., number of burrows at the nearest sampled 1-ha plot/distance to the plot), firefreq – number of times the area burned from 1957 to 2013, human – % human disturbance within a 0.79 km2 area, season – binary variable to account for within season decline in active burrows (Van Horne et al. 1997b), shrub – plot-level % cover of shrub functional group, shrubland – % shrubland within a 0.79 km2 area, and soil texture – % surface soil passing through a #4 sieve.
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v v Article e013071v
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1Department of Fish and Wildlife Sciences, University of Idaho, Moscow, Idaho 83844-1136 USA
2U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, Boise, Idaho 83706 USA
3Department of Statistical Science, University of Idaho, Moscow, Idaho 83844-1104 USA
Citation:
             
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Abstract.    Artemisia tridentata        
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Taxidea tax-
us        
Urocitellus mollis
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
 
  

 


    

          

Key words:     Artemisia tridentata   Bromus tectorum  
Taxidea taxusUrocitellus mollis
Received
†E-mail:
Copyright:  

v v Article e013072 v www.esajournals.org
HOLBROOK ET AL.
IntroductIon





     
 
        
        
       


    

    

 
       
    

     
      
      
    

 
   Artemisia tridentata)
     
     
  Taxidea taxus  
Urocitellus mollis



sensu


    
    
     
   
  
       

Athene cunicularia 

   
      
     
   



     
     



     
     

     

    




    
      
    


       
    

     
      

    
       


     
      
    





    
      


      
     
     
    

v v Article e013073 v www.esajournals.org
HOLBROOK ET AL.
     
 

    
  A. t. wyomingensis
 

      Bromus
tectorum       
     2  
 2       
  
      


    
    
        
      

     

      
  

       
     
      
     
   
      
     
      
     
      






    
       
    
 


     
     
     
     
    
       

    

     
     
     
    

(Urocitellus mollisTaxidea taxus
             


v v Article e01307 v www.esajournals.org
HOLBROOK ET AL.

     
  
     


   




       a
 
     
  
 

      

Methods
Study area and sampling
      
      


2

       
    
      
     

       
       
     
      
     
(A. t. wyomingensisKrascheninnikovia
lanataAtriplex confertifolia
    Poa
secunda     
       
  
       a,
b
       
  
     
     
    

n = 
(Urocitellus mollis   Taxidea taxus    

v v Article e01307 v www.esajournals.org
HOLBROOK ET AL.
      



       
      
     
     
   
   
     

      

     



       

Badger and ground squirrel surveys
       
  
    


      
   
     
     

       
       
        

a, b     
     
     
      
       b) in
    
      
   
     
        
      


    


          

        

Dipodomys
b
      
  

       
      
       
        
      
      

    


     



        
      
      

      
      
      


       



 
       

     
     



Environmental data
Abiotic and biotic factors 
   
      
    
v v Article e013076 v www.esajournals.org
HOLBROOK ET AL.
    
    
     
      
    
    
     

     


      
      
     

    
     
       
        
       
         
     
     
    
      
    
         
      
      


     




        

   
     
       
     

  2


2 
      
   
 


      
     




     
     

     

  


     

      
    



   
       
      


  

     
      
      
       
   



    
      




      
       
     




       
v v Article e013077 v www.esajournals.org
HOLBROOK ET AL.
          

 


      

      
       
    
    
    


    
      
     
   
     
      
      
  
      

  
Artemisia


     
      
     



     
      




     

       
       
      
     
 
       
      
    
      

    
       

1∕(
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xd1,d2,d3,d4)2
  d   
        

̄
x


      
      
     


       

       

      


     
      

Ecosystem stressors: the re- cheatgrass cycle
       


     
        
     
       

     

      



        
     
       
      

   
       
  
       
      
      
    
    
v v Article e01307 v www.esajournals.org
HOLBROOK ET AL.


       
         
   
       

     
      

      

     

    

Data analysis
   
    


(xi−
̄
x)∕(2× σ)
xi
  i     


     
        

     
 
   
     
  
     
     
       
       
     
   
      
     
     
      


    



      



  
    
  b   
        

       
     
     
     


c

c    
    
c       

     
  c     
       

      
       


      

      
     
 c   

     
    
      
 
      

     
  





    

     
  
    
v v Article e01307 v www.esajournals.org
HOLBROOK ET AL.

    



     
    

     
     
     



      


     


     
       
     
     
   

       

      



results
     
   
       
       
       
      


       
      
      
      
      

      
     
      
     
       
    r =  n = 30)

         
  
Occupancy
     
      
      
    
wi        
      
       
      Χ2  
   P = .  

        
      
     
      
      
      
       

    
     
     
   
   
c < 6 (wi 
 c

  
    
       
       
       
(Χ2P = 
  


     
     
    

       

       
v v Article e0130710 v www.esajournals.org
HOLBROOK ET AL.
      
      

Abundance
  
    
   cwi  
c
      

    
      
    
     
      
      
   ρ    
   c     
    ρ   

      
      


    

 x     
Urocitellus mollis
       
   
      


         


(Urocitellus mollis


        k  wi.        

  k  wi
    0 
      
 

7   
  3   
  2   




   
  3   
      
  2   
  3   
  3   
  2   
  2   
      
  3   
  2   
      
v v Article e0130711 v www.esajournals.org
HOLBROOK ET AL.
     
      
    
     
 
     
     
 
      
      
      

      
 


       
       
      
      
     


     
       
             
(Taxidea taxus   
c

kwi

  kccwi
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
 3 0†


    †
  2  †


    †


     




6   
  2  0
  2  0
  2  0
  2  0
  2  0
  2  0
  3  0
†
    

 x     
(Taxidea taxus
  top model     


       
         
Urocitellus
mollis       
2  

v v Article e0130712 v www.esajournals.org
HOLBROOK ET AL.
     

dIscussIon
       
     

       

     
     
      
    
     
     
       
     
     
     



     
  
   

Urocitellus mollis        
c
k
wiρ

  kccwiρ


RA

11  0†


RA

10   †



RA


12   †


RA

11    


RA

    
 RA     
 RA 7   
 RA     
 RA 6   
 RA     
 RA    
 RA     
 RA 6   
 RA     
 RA     
 RA     
 RA     
 RA     
 RA

    
 RA     
 RA     
 RA     
 RA 6   
 RA

10    
 RA     
†
v v Article e0130713 v www.esajournals.org
HOLBROOK ET AL.
        
xUrocitellus mollis
top model        
   
Bromus tectorum
                
2
 b
2

x
n = 
Urocitellus mollis
          

v v Article e01307 v www.esajournals.org
HOLBROOK ET AL.
     
   
       

     
    
      
       
     

      
       
     

  
     
     
     
  
Effects of abiotic and biotic factors
      
     
      

      
     
          

     
       
      
      
     
     
       
   Urocitellus colum-
bianus   
     
      
    
       

     
     
      
         
      
Urocitellus endemicus
      
     
    

     
      

     
      
   
     
     
     

 Spermophilus parryii  

     
    
    
     

   
       
      

      
      
      
   
  
    

     
       

      
   
      

      
   
      
Ochotona curzoniae
Vulpes
ferrilata  


Felis silvestris silvestris
     



      
v v Article e01307 v www.esajournals.org
HOLBROOK ET AL.
     
       
  






      
     
     
     




       
     



     
       


   
    


    
      
    
      

    
    



     
   
     
      


      



     
      


      

   

     



      





   
     

        
       


 
    



     
     
      
     


      
     



   
      
  
        
       
       
      
   


  
v v Article e0130716 v www.esajournals.org
HOLBROOK ET AL.

    
      
      
      


Effects of ecosystem stressors: The fire- cheatgrass
cycle
     

     
       

     
       
     
    
   
  
     
      
      
     
    

       
    
      
    

        
     
    

     
        
    
     
    
          
      
      
        

      
     
     
       
      
 
      
       
      
     
       
     
     
 



       

     
      


 
      

    
      



  

   

     
       
 

     




      
    
     
     
     a    


    
     
      


v v Article e0130717 v www.esajournals.org
HOLBROOK ET AL.
      

    

      


Implications
    
       
     
          
       
       
      
      
    
       
      
    
   
    

      
       
     
      
        
     
      
      
       
     
     
       
      
      
        
     
     

     
      
   

      
     

       
      
      
    
    
     
     


     
   
     
     

    
      
         
      



        
 


      
   




      

AcknowledgMents
       
        
        

      
       
     
       
       


        
    
lIterAture cIted
        
      
v v Article e01307 v www.esajournals.org
HOLBROOK ET AL.
     









     

      


    
       
  


      


          




 
    
    

       
      



 
       

   

    





           
    
      



Chthamalus stellatus

     
     



     

   
     
     
      

      
       
 
    


     


  


      
Taxidea taxus
    

     Taxidea taxus 
      
    

Taxi-
dea taxus   
  




     

 
    



    



 

        

v v Article e01307 v www.esajournals.org
HOLBROOK ET AL.
    






Taxidea taxus)
Cynomys leucurus

  

     

        
     


       
     





      
      
    
       

         


  

     

       







        


   

        
 


   


 

       

        


       
     
     
 

   
       






in


     




       
      

     


    
       
Meles meles

    
       

       
 


 






    
v v Article e0130720 v www.esajournals.org
HOLBROOK ET AL.



      
       


        
     

       


         
    
     
   in     
     
       


          
       
    
     
       

 

      
   


    
      

     


 

        
      



     
      

   
    
    

         
    
   










    



Meriones hurrianae

Spermophilus townsendii



     

 

      

  



  
     

 

  







   
a
     
     


b
   

  
     
v v Article e0130721 v www.esajournals.org
HOLBROOK ET AL.
      

     
      

       
   Spermophilus colum-
bianus







  


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supportIng InforMAtIon
        

... Even management efforts aimed at reducing fire risk in sagebrush steppe can change the composition of available habitat over large areas (e.g., fuel breaks; Shinneman et al., 2019). Not surprisingly, fire can also impact the composition of sagebrush-steppe animal communities across a variety of taxa and trophic levels (Holbrook et al., 2016;Knick et al., 2003;Rhodes et al., 2010;Rohde et al., 2019). Understanding the responses of animal populations to large fires is critical for identifying conservation strategies that are likely to benefit sensitive species (Nimmo et al., 2021). ...
... Wildfire has increased in frequency, severity, and scale in recent decades across the sagebrush biome (Baker, 2006;Balch et al., 2013;Pilliod et al., 2017). Despite known detrimental effects of wildfire on sagebrush-steppe plant and animal communities (Holbrook et al., 2016;Knick et al., 2003;Reeves et al., 2018), the ways in which large-scale wildfire modifies patterns of animal space use in the vegetation patches that remain are less understood. Sage-grouse are commonly thought of as an indicator species for the conservation of endemic sagebrush wildlife (Rowland et al., 2006), and disturbances affecting the habitat for sage-grouse also affect sympatric species. ...
Effects of large-scale disturbance on animal space use: Functional responses by greater sage-grouse after megafire
Article
Full-text available
  • Apr 2023
Global change has altered the nature of disturbance regimes, and megafire events are increasingly common. Megafires result in immediate changes to habitat available to terrestrial wildlife over broad landscapes, yet we know surprisingly little about how such changes shape space use of sensitive species in habitat that remains. Functional responses provide a framework for understanding and predicting changes in space use following habitat alteration, but no previous studies have assessed functional responses as a consequence of megafire. We studied space use and tested for functional responses in habitat use by breeding greater sage- grouse (Centrocercus urophasianus) before and after landscape- level changes induced by a >40,000 ha, high-intensity megafire that burned sagebrush steppe in eastern Idaho, USA. We also incorporated functional responses into predictive resource selection functions (RSFs) to map breeding habitat before and after the fire. Megafire had strong effects on the distribution of available resources and resulted in context-dependent habitat use that was heterogeneous across different components of habitat. We observed functional responses in the use and selection of a variety of resources (shrubs and herbaceous vegetation) for both nesting and brood rearing. Functional responses in the use of nesting habitat were influenced by the overarching effect of megafire on vegetation, whereas responses during brood rearing appeared to be driven by individual variation in available resources that were conditional on nest locations. Importantly, RSFs built using data collected prior to the burn also had poor transferability for predicting space use in a post-megafire landscape. These results have strong implications for understanding and predicting how animals respond to a rapidly changing environment, given that increased severity, frequency, and extent of wildfire are consequences of global change with the capacity to reshape ecosystems. We therefore demonstrate a conceptual framework to better understand space use and aid habitat conservation for wildlife in a rapidly changing world.
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... In southwestern Idaho, USA for example, the cheatgrass-fire cycle is burning so frequently that the area has experienced a vast conversion of shrub-steppe to mostly annual grasslands intermixed with some fire-resistant perennial bunchgrasses, such as Poa secunda (Knick & Rotenberry, 1997, Davies et al., 2012, Shi et al., 2018, Barker et al., 2019. This widespread shrubland to grassland conversion has altered plant diversity, vegetation structure, soil crusts, and bare ground to such an extent that habitats and microhabitats of most sagebrush steppe-associated wildlife are now fundamentally different (Freeman et al., 2014, Dumroese et al., 2015, Coates et al., 2016, Holbrook et al., 2016. ...
... Our findings suggest that the cheatgrass-fire cycle negatively impacts lizards and snakes, but some species may be more affected than others. Unfortunately, few comparisons are available for a few taxa (but see Holbrook et al., 2016), which is worrisome given the occurring ecological transformations. Thus, a call for more research is warranted for further investigation on reptiles, and other taxa. ...
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... Cheatgrass invasion is considered a significant ecological issue throughout the Great Basin (Mack 1981, Knapp 1996, Smith et al. 2022). Cheatgrass has invaded and established monoculture plant communities in many areas, often leading to reduced perennial plant diversity, disrupted vertebrate and invertebrate communities, and exacerbated fire regimes in the Great Basin (Knapp 1996, Balch et al. 2013, Chambers et al. 2014, Freeman et al. 2014, Holbrook et al. 2016, Cumberland et al. 2017, Bradley et al. 2018, Williamson et al. 2020. Increased fire and decreased biodiversity associated with increased cheatgrass presence may negatively impact sage-grouse habitat and recruitment , Miller et al. 2011, Chambers et al. 2014. ...
Nonnative ungulate impacts on greater sage-grouse late brood-rearing habitat in the Great Basin, USA
Article
Full-text available
  • Aug 2023
Domestic livestock grazing is the dominant land use on much of the current range inhabited by greater sage-grouse (Centrocercus urophasianus; sage-grouse) in the western United States. Nonnative feral horses (Equus ferus caballus) also inhabit important sage-grouse seasonal habitats. Overabundant feral horse populations and improper grazing by domestic cattle (Bos taurus) can impact the health of sagebrush (Artemisia spp.) and desert shrub rangeland communities and native wildlife. These impacts to sage-grouse can be exacerbated when they affect late brood-rearing habitat, which provide the forbs and arthropods required to fledge broods. Managers require better information regarding the extent of these impacts. In 2020, we assessed the potential impact of feral horses and domestic cattle on sage-grouse late brood-rearing habitats in western Utah and eastern Nevada, USA. We acquired late brood-rearing location data from sage-grouse marked with global positioning system and very-high frequency radio-transmitters from both east and west Nevada data to delineate late brood-rearing habitats. Using these location data, we compared 8 sites (4 pairs) within horse and non-horse use areas to assess sage-grouse habitat quality characteristics between areas that have been predominantly horse and cattle grazed versus sites that have been predominantly cattle grazed. For each pairing, 1 site was located within and the other outside of a Bureau of Land Management herd management area boundary, and both sites shared similar habitat characteristics (i.e., topography, dominant vegetation, soils, and climate) and selection probability for broods. We collected vegetation and dung count data at each site to assess characteristics related to habitat quality for sage-grouse brood-rearing, based on ungulate presence. We used a mixed model analysis of variance to detect differences between each paired site comparison (α < 0.01). Horses or evidence of horse presence (i.e., dung) were not detected at our non-horse sites allowing for an unbiased comparison between paired sites. Cattle presence was noted at all our paired sites. Average annual grass frequency was 0.74 in horse and 0.17 in non-horse use areas (P = 0.20), and average annual grass cover was 4.0% compared to 0.2% in horse use areas (P = 0.32). Average annual grass biomass was 0.45 kg/ ha in horse and 0.04% in non-horse use areas (P = 0.34). Vegetation height was 44.2 cm in non-horse compared to 34.5 cm in horse use areas (P = 0.23). These results suggest that increased ungulate grazing and year-long use of late brood-rearing habitat by feral horses coupled with livestock grazing may impair habitat suitability, particularly considering ecological impacts from invasive plant species. Our results suggest that managing late brood-rearing habitats to reduce the frequency and intensity of year-long grazing by feral horses can be best accomplished by reducing horse numbers and the seasonal distribution of grazing by domestic livestock.
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... Thus, in our study, the occupancy probability should be interpreted as the "probability of use" of the site. This type of modeling has been widely applied in studies that aim to identify environmental factors affecting the use of different habitats by species, including fire occurrence [87][88][89][90]. ...
Species-Specific Responses of Medium and Large Mammals to Fire Regime Attributes in a Fire-Prone Neotropical Savanna
Article
Full-text available
  • Mar 2023
Fire occurrence affects the distribution of key resources for fauna in natural ecosystems worldwide. For fire management strategies adequate for biodiversity conservation, the understanding of how species respond to fire-induced changes is essential. In this study, we investigated the role of fire regimes on spaces used by medium and large mammals at multiple spatial scales (0.8 ha to 78.5 ha) in a fire-prone savanna ecosystem (Brazilian Cerrado). We sampled mammals using 60 camera traps distributed in 30 sampling units located in grassland and typical savanna formations. We applied single-species occupancy models and AIC-based model selection to assess how mammals use the space in response to pyrodiversity (both diversity of fire frequencies and diversity of fire ages), the proportion of recently burned area, and the proportion of long-unburned area while accounting for detectability. Our results showed that fire regime variables affected the study species differently. Deer species used the space regardless of mosaic pyrodiversity and the proportion of specific fire ages. Fire-related variables, however, affected space use by tapirs and maned wolves. Tapirs preferred to use fire mosaics with lower diversity of fire frequencies, whereas maned wolves more intensively used mosaics with high fire age diversity and a high proportion of recently burned areas. Based on our findings, we recommend that fire management targeting specific mammal species should not necessarily focus on maximum pyrodiversity. Instead, we suggest a management strategy combining "patch mosaic burning" with the maintenance of specific fire-age patches suitable for different species' requirements.
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... Although these mechanisms are usually evaluated individually, they can affect species occupancy and abundance simultaneously [15], with the relative importance of each mechanism being dependent on spatial scale [1]. Moreover, biotic and abiotic factors [16] as well as stochastic dynamics [17] also affect species abundance and occupancy patterns. This combined effect of different factors affecting species abundance and occupancy might explain why some taxa do not show positive abundance-occupancy relationships [18,19] as well as why these positive relationships are usually weak [1,4]. ...
Effects of occupancy estimation on abundance–occupancy relationships
Article
Full-text available
Abundance–occupancy relationships predict that species that occupy more sites are also more locally abundant, where occupancy is usually estimated following the assumption that species can occupy all sampled sites. Here we use the National Ecological Observatory Network small-mammal data to assess whether this assumption affects abundance–occupancy relationships. We estimated occupancy considering all sampled sites (traditional occupancy) and only the sites found within the species geographic range (spatial occupancy) and realized environmental niche (environmental occupancy). We found that when occupancy was estimated considering only sites possible for the species to colonize (spatial and environmental occupancy) weaker abundance–occupancy relationships were observed. This shows that the assumption that the species can occupy all sampled sites directly affects the assessment of abundance–occupancy relationships. Estimating occupancy considering only sites that are possible for the species to colonize will consequently lead to a more robust assessment of abundance–occupancy relationships.
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Rangeland Biodiversity
Chapter
Full-text available
  • Sep 2023
In its simplest form, biodiversity is defined as species richness (the number of species in a given area). More complex definitions include the variety of life on Earth, from genes to ecosystems, and include the ecological and evolutionary processes that sustain that life. As in other ecosystems, biological communities in rangelands are influenced by a number of different abiotic and biotic drivers or “filters” at both broad and fine scales, and an understanding of these processes is critical for maintaining ecosystem services as well as addressing widespread biodiversity declines. In rangeland ecosystems specifically, the primary threats to biodiversity are habitat loss, fragmentation, and degradation through mismanagement, which includes suppression or mis-application of historical disturbance regimes. Restoring heterogeneity to rangelands by mimicking historical disturbance regimes has been shown to benefit biodiversity, but the exact role of disturbance varies widely throughout North American rangelands. As such, careful consideration of the type, duration/periodicity, intensity, and spatial and temporal extent and configuration of these disturbances is necessary when managing for site-specific biodiversity outcomes. It is important to consider the effects of both inherent (i.e., either natural or historical) and human-caused variability on rangeland plant and wildlife communities. In the future, practitioners should promote management practices that maintain and enhance biodiversity to maximize ecosystem functions and services that improve the quality and quantity of economic (e.g., livestock production, carbon banking) and ecological (e.g., biodiversity, sustainability) outcomes in North American rangelands.
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Mesocarnivores of Western Rangelands
Chapter
Full-text available
  • Sep 2023
There are 22 species of mesocarnivores (carnivores weighing < 15 kg) belonging to five families that live in rangelands of the western United States. Mesocarnivores are understudied relative to large carnivores but can have significant impacts on ecosystems and human dimensions. In this chapter, we review the current state of knowledge about the biology, ecology, and human interactions of the mesocarnivores that occupy the rangelands of the central and western United States. In these two regions, mesocarnivores may serve as the apex predator in areas where large carnivores no longer occur, and can have profound impacts on endemic prey, disease ecology, and livestock production. Some mesocarnivore species are valued because they are harvested for food and fur, while others are considered nuisance species because they can have negative impacts on ranching. Many mesocarnivores have flexible life history strategies that make them well-suited for future population growth or range expansion as western landscapes change due to rapid human population growth, landscape development, and alterations to ecosystems from climate change; however other mesocarnivores continue to decline. More research on this important guild is needed to understand their role in western working landscapes.
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The importance of habitat type and historical fire regimes in arthropod community response following large-scale wildfires
Preprint
Full-text available
  • Jul 2023
Wildfires are increasingly altering ecosystems, posing significant challenges for biodiversity conservation and ecosystem management. In this study, we used DNA metabarcoding to assess the response of arthropod communities to large-scale wildfires across diverse habitat types. We sampled six reserves within the University of California Natural Reserve System (UCNRS), each which was partially burned in the 2020 Lightning Complex wildfires in California. Using yellow pan traps to target pollinators, we collected arthropods from burned and unburned sites across multiple habitat types including oak woodland, redwood, scrub, chamise, grassland, forest, and serpentine habitats. We found no significant difference in alpha diversity values between burned and unburned sites; instead, seasonal variations played a significant role in arthropod community dynamics, with the emergence of plant species in Spring promoting increased pollinator richness at all sites. Compositional similarity analysis revealed that burn status was not a significant grouping factor when comparing all sites. Instead, community composition primarily varied across reserves, indicating distinct pools of arthropods structured geographically. Habitat type played a crucial role in determining the response of arthropod communities to fire. While communities in grasslands and oak woodlands exhibited recovery following burn, scrublands experienced substantial changes in community composition. Our study highlights the importance of examining community responses to wildfires across broad spatial scales and diverse habitat types. By understanding the nuanced dynamics of arthropod communities in response to fire disturbances, we can develop effective conservation strategies that promote resilience and maintain biodiversity in the face of increasing wildfire frequency and intensity driven by climate change.
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The importance of habitat type and historical fire regimes in arthropod community response following large-scale wildfires
Preprint
  • Jul 2023
Wildfires are increasingly altering ecosystems, posing significant challenges for biodiversity conservation and ecosystem management. In this study, we used DNA metabarcoding to assess the response of arthropod communities to large-scale wildfires across diverse habitat types. We sampled six reserves within the University of California Natural Reserve System (UCNRS), each which was partially burned in the 2020 Lightning Complex wildfires in California. Using yellow pan traps to target pollinators, we collected arthropods from burned and unburned sites across multiple habitat types including oak woodland, redwood, scrub, chamise, grassland, forest, and serpentine habitats. We found no significant difference in alpha diversity values between burned and unburned sites; instead, seasonal variations played a significant role in arthropod community dynamics, with the emergence of plant species in Spring promoting increased pollinator richness at all sites. Compositional similarity analysis revealed that burn status was not a significant grouping factor when comparing all sites. Instead, community composition primarily varied across reserves, indicating distinct pools of arthropods structured geographically. Habitat type played a crucial role in determining the response of arthropod communities to fire. While communities in grasslands and oak woodlands exhibited recovery following burn, scrublands experienced substantial changes in community composition. Our study highlights the importance of examining community responses to wildfires across broad spatial scales and diverse habitat types. By understanding the nuanced dynamics of arthropod communities in response to fire disturbances, we can develop effective conservation strategies that promote resilience and maintain biodiversity in the face of increasing wildfire frequency and intensity driven by climate change.
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Long-Term Persistence of Desert Rodent Species in a Great Basin Sagebrush Community: Potential Effects of Fire, Invasive Annuals, and Warming Temperatures
Article
  • Oct 2022
To test long-term stability of a desert rodent community and potential impacts of wildfire on the community's stability, we live-trapped desert rodents from 2019 to 2021 at a site in western Nevada where we had previously trapped from 1989 to 1993. Trapping occurred in unburned sagebrush (Artemisia tridentata) and in adjacent burned habitat where sagebrush cover was removed by a fire in 1985. We also used online data to test for trends in estimated cover of annual and perennial vegetation and in ambient temperatures and precipitation over the >30-year period spanned by the trapping data. White-tailed antelope squirrels (Ammospermophilus leucurus) were captured significantly more frequently in unburned habitat than in burned habitat, and though they were previously captured (infrequently) in the burned habitat, they were not captured there in new trapping efforts. Among heteromyid rodent species, 2 kangaroo rats (Merriam's kangaroo rat [Dipodomys merriami] and Panamint kangaroo rat [D. panamintinus]) were also captured significantly more often in unburned sagebrush habitat than in burned habitat. Habitat affinities of Panamint kangaroo rats switched over time, as they were previously captured more often in burned habitat but were much more common in the unburned habitat in new trapping sessions. Ord's kangaroo rat (D. ordii) was the only species captured significantly more often in the burned habitat, where their capture frequencies have also increased in comparison with old data. Three heteromyid species that were previously captured (infrequently) were not trapped in new trapping sessions. These apparent changes in rodent numbers over time were accompanied by increased ambient temperatures and, in the burned habitat, by an increase in annual plant cover (mainly introduced cheatgrass [Bromus tectorum]) and a decrease in herbaceous perennials (mainly Indian ricegrass [Achnatherum hymenoides]). Changes in the rodent community probably resulted from these vegetation changes, which in turn may at least partly result from the warming trend. Para probar la estabilidad a largo plazo de una comunidad de roedores del desierto y el potencial impacto de los incendios forestales en la estabilidad de la comunidad, capturamos roedores del desierto desde 2019 hasta 2021 en un sitio en el oeste de Nevada, donde previamente capturamos roedores desde 1989 hasta 1993. Las tram-pas se colocaron en arbustos no quemados (Artemisia tridentata) y en un hbitat quemado adyacente, donde en 1985 un incendio elimin los arbustos. Tambin, utilizamos datos disponibles en lnea para comprobar las tendencias en la cobertura estimada de la vegetacin anual y perenne, y en las temperaturas ambientales y las precipitaciones durante el periodo de ms de 30 aos que abarcan los datos de trampeo. Se capturaron ardillas antlope de cola blanca (Ammospermophilus leucurus) con mucho mayor frecuencia en el hbitat no quemado comparado con el quemado, y aunque previamente se capturaban con poca frecuencia en el hbitat quemado, no fueron encontradas en ese hbitat durante nuevos intentos de trampeo. Entre las especies de roedores hetermidos, dos ratas canguro (la rata canguro de Merriam [Dipodomys merriami] y la rata canguro de Panamint [D. panamintinus]) tambin se capturaron con mucha ms frecuencia en el hbitat de arbustos no quemados. Las tendencias de uso de hbitat de la rata canguro de Panamint cambiaron a travs del tiempo, ya que previamente se capturaban con mayor frecuencia en el hbitat quemado, sin embargo, fueron mucho ms comunes en el hbitat no quemado en las nuevas sesiones de trampeo. La rata canguro de Ord (D. ordii) fue la nica especie capturada significativamente ms a menudo en el hbitat quemado, donde sus frecuencias de captura tambin han aumentado en los nuevos datos comparados con los antiguos. Tres especies de hetermidos que antes se capturaban con poca frecuencia no fueron encontrados en las nuevas sesiones de trampeo. Estos cambios evidentes en el nmero de roedores a lo largo del tiempo estuvieron acompaados por un aumento en las temperaturas ambientales y, en el hbitat quemado, por un aumento de la cubierta vegetal anual (principalmente el pasto espiguilla introducido [Bromus tectorum]) y una disminucin de las plantas herbceas perennes (principalmente el ricino indio [Achnatherum hymenoides]). Los cambios en la comunidad de roedores probablemente fueron consecuencia de estos cambios en la vegetacin, que a su vez pueden ser resultado, al menos en parte, de la tendencia al aumento de temperatura.
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Teetering on the Edge or too Late? Conservation and Research Issues for Avifauna of Sagebrush Habitats
Article
Full-text available
  • Nov 2003
Degradation, fragmentation, and loss of native sagebrush (Artemisia spp.) landscapes have imperiled these habitats and their associated avifauna. Historically, this vast piece of the Western landscape has been undervalued: even though more than 70% of all remaining sagebrush habitat in the United States is publicly owned, <3% of it is protected as federal reserves or national parks. We review the threats facing birds in sagebrush habitats to emphasize the urgency for conservation and research actions, and synthesize existing information that forms the foundation for recommended research directions. Management and conservation of birds in sagebrush habitats will require more research into four major topics: (1) identification of primary land-use practices and their influence on sagebrush habitats and birds, (2) better understanding of bird responses to habitat components and disturbance processes of sagebrush ecosystems, (3) improved hierarchical designs for surveying and monitoring programs, and (4) linking bird movements and population changes during migration and wintering periods to dynamics on the sagebrush breeding grounds. This research is essential because we already have seen that sagebrush habitats can be altered by land use, spread of invasive plants, and disrupted disturbance regimes beyond a threshold at which natural recovery is unlikely. Research on these issues should be instituted on lands managed by state or federal agencies because most lands still dominated by sagebrush are owned publicly. In addition to the challenge of understanding shrubsteppe bird-habitat dynamics, conservation of sagebrush landscapes depends on our ability to recognize and communicate their intrinsic value and on our resolve to conserve them. ¿Tambaleando en el Borde o Demasiado Tarde? Asuntos de Conservación e Investigación para la Avifauna de Ambientes de Matorral de Artemisia spp Resumen. La degradación, fragmentación y pérdida de paisajes nativos de matorrales de Artemisia spp. han puesto en peligro a estos ambientes y su avifauna asociada. Históricamente, esta vasta porción del paisaje occidental ha sido subvalorada: aunque más del 70% de todo el hábitat de matorral de Artemisia de los Estados Unidos es de propiedad pública, <3% de éste es protegido por reservas federales o parques nacionales. En este artículo revisamos las amenazas a las que se enfrentan las aves de los matorrales de Artemisia para enfatizar la urgencia de emprender acciones de conservación e investigación, y sintetizamos la información existente que constituye la base para una serie de directrices de investigación recomendadas. El manejo y conservación de las aves de los matorrales de Artemisia necesitará más investigación en cuatro tópicos principales: (1) la identificación de prácticas primarias de uso del suelo y su influencia sobre los ambientes y las aves de Artemisia, (2) un mejor entendimiento de las respuestas de las aves a componentes del hábitat y a procesos de disturbio de los ecosistemas de Artemisia, (3) el mejoramiento de diseños jerárquicos para programas de censos y monitoreos y (4) la conexión de los movimientos de las aves y los cambios poblacionales durante la migración y en los períodos de invernada con la dinámica en las áreas reproductivas de matorrales de Artemisia. Estas investigaciones son esenciales porque ya hemos visto que los ambientes de Artemisia pueden ser alterados por el uso del suelo, la diseminación de plantas invasoras y la disrupción de los regímenes de disturbio más allá de un umbral en el que la recuperación natural es poco probable. La investigación en estos asuntos debe instituirse en tierras manejadas por agencias estatales o federales porque la mayoría de las tierras aún dominadas por Artemisia son de propiedad pública. Además del desafío de entender la dinámica aves-hábitat en las estepas arbustivas, la conservación de los paisajes de matorral de Artemisia depende de nuestra habilidad de reconocer y comunicar su valor intrínseco y de nuestra decisión para conservarlos.
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Post-Fledging Dispersal of Burrowing Owls in Southwestern Idaho: Characterization of Movements and use of Satellite Burrows
Article
Full-text available
  • Feb 2001
Using radiotelemetry, we monitored dispersing juvenile Western Burrowing Owls (Athene cunicularia hypugaea) within a migratory population in southwestern Idaho during 1994 and 1995. Owls remained within natal areas for an average (± SE) of 58 ± 3.4 days post-hatching before moving permanently beyond 300 m, which was our operational cutoff for dispersal from the natal area. On average, owls dispersed on 27 July (range: 15 July to 22 August), which was approximately 4 weeks after fledging. After initiating dispersal, juveniles continued moving farther away from their natal burrows and, by 61–65 days post-hatching, they had moved 0.6 ± 0.2 km. Each juvenile used 5.1 ± 1.2 satellite burrows, and individual satellite burrows were used for up to 14 days. The average date on which we last sighted radio-tagged juveniles was 13 August, and all but one juvenile departed the study area by early September. Our study illustrates the importance of satellite burrows to dispersing Burrowing Owls.
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Trophic Dynamics in Urban Communities
Article
  • May 2005
Articles E cologists have long debated what factors control the trophic (feeding) structure and function of ecosystems. This is more than just a matter of determining "who eats whom"; ecologists have pondered whether there are fundamental rules for determining (a) how many trophic levels an ecosystem can support, (b) how much primary production is consumed by herbivores, and (c) whether resources from the bottom of the food chain, or consumers from the top, control biomass, abundance, and species diversity in food webs. These questions are not only fundamental to ecology but essential for conservation and management. For example, the loss of a top predator in a food web that is largely controlled by top-down forces may drastically alter biodiversity and ecosystem function (e.g., nutrient cycling), whereas the same loss may have little effect in a resource-controlled (i.e., bottom-up) food web. To answer these questions, ecologists have expended an enormous effort to understand the relative importance of pre-dation or parasitism (and, to a lesser extent, mutualism) and competition for resources in trophic organization. Three basic models of control of trophic structure have emerged from this endeavor. The first of these, the energetic model of food webs, holds that energy supply (from the bottom of food webs), in concert with the relative efficiencies of consumers, limits the number of trophic levels and the relative biomass of each level in natural ecosystems (Lindeman 1942). The second model, commonly known as the "green world" hypothesis (Hairston et al. 1960), states that predators and parasites exert top-down control on herbivore populations. According to this model, herbivores do not generally compete with each other, and plant resources are not limiting because herbivore population densities remain low as a result of top-down control. The third model (Menge and Sutherland 1987) hypothesizes that the relative effects of predation on species diversity vary as a function of environmental stress (e.g., exposure, desiccation, extreme temperatures) and productivity. Specifically, the Menge-Sutherland model suggests that pre-dation should be more important at low and intermediate levels of stress, because high stress limits the abundance of predators more than it limits herbivore competitors. Competition for resources should be more important at high levels of stress (and low levels of productivity). Various modifications and elaborations of these three basic models of food webs and trophic structure have proliferated in the past several decades (Oksanen et al. 1981, Power 1992). Empirical tests of the food web models, and modifications thereof, have been conducted mostly in non-human-dominated ecosystems ranging from marine environments to freshwater lakes and streams, tundra, deserts, forests, and grasslands, each test often producing a different answer (Con-nell 1983, Schoener 1983, Sih et al. 1985). Empirical tests and the development of theory for food web dynamics have historically involved human-dominated ecosystems, such as agroecosystems (Rosenheim 1998), or recovering agricul-Stanley H. Human activities dramatically change the abundance, diversity, and composition of species. However, little is known about how the most intense human activity, urbanization, alters food webs and trophic structure in biological communities. Studies of the Phoenix area, situated amid the Sonoran Desert, reveal some surprising alterations in the control of trophic dynamics. Species composition is radically altered, and resource subsidies increase and stabilize productivity. Changes in productivity dampen seasonal and yearly fluctuations in species diversity, elevate abundances, and alter feeding behaviors of some key urban species. In urban systems-in contrast to the trophic systems in outlying deserts, which are dominated by limiting resources-predation by birds becomes the dominant force controlling arthropods on plants. Reduced predation risk elevates the abundance of urban birds and alters their foraging behavior such that they exert increased top-down effects on arthropods. Shifts in control of food web dynamics are probably common in urban ecosystems, and are influenced by complex human social processes and feedbacks.
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Modern Applied Statistics with S
Book
  • Jan 2002
A guide to using S environments to perform statistical analyses providing both an introduction to the use of S and a course in modern statistical methods. The emphasis is on presenting practical problems and full analyses of real data sets.
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MuMIn: Multi-model inference
Code
  • Jan 2013
Tools for performing model selection and model averaging. Automated model selection through subsetting the maximum model, with optional constraints for model inclusion. Model parameter and prediction averaging based on model weights derived from information criteria (AICc and alike) or custom model weighting schemes. [Please do not request the full text - it is an R package. The up-to-date manual is available from CRAN].
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