Phenology, or the timing of life history events, is dramatically changing across species and landscapes in response to global change. Phenological responses can be heterogeneous across both communities and landscapes, varying across a wide variety of spatiotemporal scales. Synthesizing information across these different scales of measurement and inference may uncover scaling relationships with important ecological consequences. Constructing scaling relationships is necessary for forming null expectations about how spatial and temporal resolution influence conclusions drawn from particular scales of measurement, explaining mismatches between data measured at different scales (e.g. field surveys and remote sensing), and predicting relationships at scales that are not measured empirically. Such an effort first requires assessing the scales at which phenology is measured. We therefore review literature in the field of landscape phenology, and synthesize information in these studies around a set of core concepts. From this, we identify strong trends and important gaps in phenological sampling. We also develop an empirically-informed simulation method for virtual landscapes and species, to elucidate the inherent sensitivities of phenological metrics to measurement scale, independent of other factors, such as exogenous climate forcings.
Results/Conclusions
We demonstrate that the properties of multiple phenological events change distinctly from one another, but predictably with spatial and temporal measurement scale. In particular, we identify that the timing of the beginning of an event (e.g., First Flower), can be especially sensitive to the spatial and temporal grain (or resolution) of observations. Our work provides an initial assessment of the role of observation scale in landscape phenology, and a general approach for measuring and reporting scale-dependence. We thus set the stage for a new generation of empirical research in the field that builds off of multi-scale observations to understand how phenology across Earth’s ecosystems respond to environmental variability and change.