Figure 1.

Some potential scenarios that can happen in optical remote sensing of vegetation canopies. The graph shows sources of variation in the relationship between species and optical types. Plants of different species might belong to different optical types, but many other situations can also be found. Optical types can be related to information of interest (e.g., species or plant traits) or to irrelevant pattern (e.g., shadows, depending on the research question). Scenario (a) represents a stand with individuals of only one single species, with a similar reflectance. In scenario (b) individuals of two species have a similar reflectance; hence they would be grouped in the same spectral species. This is further complicated once mixing individuals belonging to the same taxon but to different optical types (c) or individuals of multiple species belonging to different optical types that do not follow the species boundaries (d). What many would hope for is that plants of different species belong to different optical types, which may happen (e). Finally, the same plant individual can consist of different optical types showing different spectral properties in for example, young versus old leaves, shadow and light, or differences in health conditions. This intra‐individual mixing property will be related to all of the previous cases (f)–(h). Note that a stand or individual can pass through several of these scenarios in time (intra and interannual variability).