OPS 1-10
Findings from the USA National Phenology Network's Green Wave Campaign
A near real-time visualization of the “green wave,” or the flush of vegetative growth that accompanies tree canopy leaf-out over across the continent, has wide-ranging applications for agriculture, potential pest outbreaks, atmospheric models of carbon and water flux, and it even offers insight into the best time to plan an outdoor wedding to avoid allergies or capitalize on fall color. Better spatial and temporal estimates of tree canopy “green-up” and “brown-down” can advance understanding of how plants are responding to varying and novel conditions.
Creation of a “green wave” product requires detailed spatio-temporal knowledge of leafing status (bud break, leaf emergence and expansion) for dominant tree species across the nation. To address this need, the USA National Phenology Network staff launched a nation-wide campaign to collect observations of leaf phenology for dominant deciduous tree species focused on maple (Acer spp.), oak (Quercus spp.), and poplar (Populus spp.) starting in March 2013. Three to eight species – selected for regional dominance, economic importance, and ease of identification and monitoring - were selected within each of eight U.S. regions. Through this campaign, individuals were encouraged to track leaf phenology of target species using the online phenology reporting program Nature’s Notebook (www.nn.usanpn.org).
Results/Conclusions
In 2013, we engaged 537 Nature’s Notebook participants in tracking one or more target species at 439 sites. We were also successful in retaining active observers at 37% of the 273 sites that had reported on target species in 2012. Overall, 109,000 phenology records on target species were submitted in 2013, though data density varied greatly by region. The greatest rates of participation occurred in the southeast and northeast regions, whereas the Great Plains and Alaska had relatively few participants. Not surprisingly, observer activity – in the form of both trees registered and trees observed – followed a seasonal cycle. Activity was greatest in the spring, slowed over the summer, and increased again in autumn.
Observations submitted through this campaign enabled us to document clear patterns of deciduous tree phenology. Leaf-out dates in spring of 2013 were much later across most of the U.S. relative to the dramatically early spring of 2012. These observations serve as the first step toward the creation of a “green wave” product that will document, predict and eventually forecast forest green-up. We will continue our Green Wave campaign focused on leaf phenophases of maples, oaks, and poplars in 2014 and over the next several years.