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. http://dx.doi.org/10.1890/14-2447.1

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

Name

Description

 

 

 

 

Habitat extent

Tree covera

TREE

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

 

 

 

 

 

 

 

 

Configuration

Number of patches 

SUBDIV

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

 

Large patch index 

AGGREG

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

 

Patch shape 

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.

 

 

 

 

 

 

 

 

Composition

Land use component 1

LUSE

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

VEGDIV

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.

 

 

 

 

 

 

 

 

Productivity

Riparian tree covera

RIPAR

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

NDVI

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".

 

 

 

 

 

 

 

 

Context

Geographic location

EAST

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

 

Distance to large remnant

SOURCE

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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