Anomalous warm spring of 2010 advances deciduous forest leaf-out: Application of the Nature's Notebook dataset and visualization analysis tool

Background/Question/Methods

Phenology, the timing of seasonal life cycle events of plants and animals, is closely tied to climatic conditions. Warmer late winter/early spring conditions can advance time of leafing and flowering in plants, which can be observed across scales ranging from organisms to landscapes or regions. Although remote sensing can be used to detect spatial and temporal patterns of phenology on landscape to regional scales, in-situ observations of organismal phenology are relatively limited across the US, with the exception of occasional long-term datasets typically for relatively few species and at relatively few locations.  Moreover, non-standardized observational protocols constrain data integration and application across broad spatial scales.  Finally, in-situ observations can be used to detect patterns of phenology (e.g., flowering, leaf initiation) not observable using other observing platforms.  The USA National Phenology Network (USA-NPN; www.usanpn.org), established in 2007, has developed and implemented a national phenology observation program, called Nature’s Notebook, which provides internationally standardized methods and protocols for phenological status monitoring for over 800 common plant and animal species.  Here, we describe preliminary results of this national program, with a focus on in-situ eastern deciduous forest tree phenology between the years 2009 and 2011, bracketing the anomalously warm spring of 2010.

Results/Conclusions

Nature’s Notebook and the associated National Phenology Database provide real-time raw data for plants (from 2009 to present) and animals (from 2010 to present), including FGDC-compliant metadata and vetted and documented methodology.  A new data visualization and exploration tool that premiered in spring 2010 allows sophisticated graphical visualization of integrated phenological and meteorological data.  We used this tool to conduct a preliminary analysis of timing of leaf emergence for 10 common overstory deciduous trees across the eastern deciduous forest in 2009-2011; observed patterns suggested phenological advancement for several, but not all, target species in 2010 relative to 2009 and 2011.  Subsequent statistical analysis using generalized linear models indicated earlier leaf emergence in 2010 for all species combined, and (by 2-3 weeks depending species) for 4 of the 10 species when examined individually; two other species showed a tendency toward earlier leaf-out in 2010 relative to 2009 and 2011. These results illustrate the value of (1) the USA-NPN visualization and analysis tool for exploring patterns in the data housed in the National Phenology Database, and (2) an integrated approach to standardized, in-situ phenological observations on a national scale with potential for a posteriori application at local to regional scales.