This section describes a number of ways in which biological factors affect measurement of geomorphic processes and suggests ways of quantifying and measuring these effects. Almost all geomorphic processes are influenced by biological factors of some kind, so that the material considered here cuts across the subdivisions of Part Four, implying that similar techniques can be used. On the other hand, biological influences are sometimes extremely complex or concern very particular aspects, and they require specially adapted measurement techniques. Therefore, only if some method is already established or if it is applicable in a wider range of research is it described; if this is not the case, or if methods from preceding sections are suitable with slight modifications, the text is confined to drawing the reader's attention to the effects that the biotic community may have on geomorphic processes.