Ecological Archives E096-272-A3

Angie Haslem, Dale G. Nimmo, James Q. Radford, and Andrew F. Bennett. 2015. Landscape properties mediate the homogenization of bird assemblages during climatic extremes. Ecology 96:31653174.

Appendix C. Table containing information about all predictor variables.

Table C1. Description of variables used to quantify the properties of study landscapes. Variables are grouped according to the type of landscape property they represent.

Landscape property

Predictor variable







Habitat extent

Tree covera


Total area of native wooded vegetation per landscape (ha); a measure of habitat extent










Number of patches 


Number of patches of native vegetation; a measure of habitat subdivision


Large patch index 


Percentage of native vegetation contained within the largest single patch in the landscape; an index of habitat aggregation


Patch shape 


The area-weighted mean of CIRCLE for all vegetation patches in the landscape, where CIRCLE = 1 – (patch area/area of smallest circumscribing circle). CIRCLE increases as patches become more irregular and elongated; a measure of the shape-complexity of habitat patches.










Land use component 1


First factor derived from a principal components analysis based on proportional cover of production-dominated land-use types; representing a gradient from cropping landscapes (dryland cropping loading =-0.65) to grazing landscapes (grazing land loading=0.74); a measure of the dominant anthropogenic land-use type.


Vegetation diversity


Shannon-Wiener diversity index (H’) of the proportional cover of Ecological Vegetation Classes within native vegetation in the landscape (i.e. within TREE); a measure of the diversity of natural vegetation types.










Riparian tree covera


Total area of wooded vegetation typical of streamsides, floodplains and wetland margins, per landscape (ha); a measure of the amount of vegetation of naturally higher fertility/moisture. Note that riparian areas commonly do not provide free water for most of the year (even in non-drought conditions).  

Normalized Difference Vegetation Index


Derived from the reflectance of the electromagnetic spectrum near the infrared and red portions, values averaged across the 10 survey sites per landscape; a measure of vegetation "greenness".










Geographic location


Easting coordinate of the center of each landscape (m); a measure of east-west gradient across landscapes.


Distance to large remnant


Mean distance (km) across sites to the closest large (>10,000 ha) remnant block; a measure of proximity to potential source populations.

a log10 transformed prior to modeling

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