Measures of Heterogeneity
Functional Heterogeneity is variation at a scale that corresponds to the function of an ecological process or property (Li and Reynolds 1995, directly quoted from Fuhlendorf et al. 2017). The scale of measurement for functional heterogeneity is determined by the ecological entity of interest, rather than arbitrarily determined by an observer. For example, the ecosystem properties important to people are not the same as the ecosystem properties important to a beetle (Fuhlendorf et al. 2017).
Measured Heterogeneity is a “measure of the variability of an ecological property or process without explicit relations to variability in animal behavior or ecological function” (Li and Reynolds 1995, directly quoted from Fuhlendorf et al. 2017). This is an important consideration for researchers, as measured heterogeneity is the act of taking measurements of heterogeneity without considering the ecological entity of interest (as in functional heterogeneity) but instead choosing measurements and sampling procedures based on what is easiest or most intuitive to the human doing the research (Fuhlendorf et al. 2017).
Spatial and Temporal Heterogeneity specifically refers to variability in an entity (e.g., a landscape) in space and time, respectively. Spatial and temporal heterogeneity are important because measures of heterogeneity will differ based on the spatial and temporal scales selected by an observer. For example, animal species are distributed differently across landscapes in space and time; their use of the landscape will vary due to spatial factors such as land cover and temporal factors such as season. Temporal heterogeneity can also be seen at a point in a crop field. The field may lack spatial heterogeneity but over time exhibits temporal heterogeneity. During the growing season, the field is mostly homogeneous, covered in one crop, but as time passes the heterogeneity increases as the field transitions from crop covered, to bare and harvested and then back to vegetated again, possibly with a different crop.