A digital photography protocol for the rapid assessment of herbaceous communities in riparian buffers

Close-range digital photography approaches represent promising tools for monitoring changes to the geometric structure of biological communities. Yet, we do not know if differences in the compositional and functional characteristics of valuable and sensitive ecosystems, such as riparian vegetation buffers, can be routinely assessed using indices of their geometric structure. We tested a photographic protocol using image texture and anisotropy indices to assess differences in the compositional (species diversity) and functional characteristics (plant height, flowering and leaf traits) of 28 herbaceous communities repeatedly surveyed over an entire growth season. Our results revealed that image texture values decrease with increasing plant height, leaf polyphenol content and species diversity. Low texture values in close-range digital images were typically associated with tall, flowering, and functionally diversified species assemblages; that is communities consisting mostly of forbs and mixed growth forms. In contrast, species assemblages dominated by grasses or sedges presented more random geometric patterns and were associated with higher image texture values. Further protocol developments will have to explore the behaviour of other image indices and to include riparian buffers comprising assemblages of shrub and tree species.

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