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Figure 5. Relationships between tree density and vegetation 
indices (VIs) 
3.2 Relationship between vegetation indices and tree 
density for the 5x5 maximum filtering algorithm for juniper 
A simple linear regression between the conventional vegetation 
indices, new TRVI vegetation index and tree density based on 
the 5x5 maximum filtering algorithm was calculated. In the 
field survey, we observed that plots with few juniper trees had 
more ground vegetation, as shown in the significant positive 
relationship. Vegetation that is dead or stressed reflects more 
red lights and less NIR light. Likewise, non-vegetated surfaces 
have much more even reflectance across the light spectrum. In 
arid and semi-arid regions, the NDVI is low, particularly in 
forests where vegetation cover is sparse compared to the soil 
background. The NDVI is sensitive to the optical properties of 
the soil background (Baret and Guyot, 1991) (Figure 6). 
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Figure 6. Relationships between tree density and vegetation 
indices (VIs) 
3.3 Relationship between new vegetation index and tree 
density for the 5x5 maximum filtering algorithm for both 
area 
In the arid and semi-arid regions, soil type is very important; 
thus, we attempted to reduce the confounding effect of the soil- 
vegetation interaction by using optimum window sizes to obtain 
spectral values for TRVI. Generally, in arid and semi-arid 
regions, the green vegetation index tends to decrease with low- 
reflecting soil backgrounds, and the influence of soil 
background has been found to seriously hamper the assessment 
and characterization of vegetation canopy cover (Huete et al. 
1985; Huete and Jackson 1987).The relationship between TRVI 
and tree density was positive. TRVI values were generally 
higher than the conventional vegetation indices(Figures 7 and 
8). 
  
  
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Figure 7. The relationship between pistachio tree density and 
TRVI vegetation index 
  
     
   
   
     
    
    
    
    
   
     
    
    
     
  
  
   
    
    
   
    
    
   
     
      
  
    
   
    
     
  
      
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