Mapping leaf-out times using satellites and ground observations

Posted by Richard B. Primack

"Rather than love, than money, than fame, give me truth."

Henry David Thoreau, Walden

Data gathered by satellites are increasingly being used in studies of plant ecology, landscape ecology, and climate change biology. Researchers from the BU Biogeosciences Program are now using data from the Landsat satellite to determine the places where trees leaf out early and leaf out late at the scale of 30 m pixels. This unprecedented level of detail allows researchers to measure and predict how present and future climate change will affect the onset of leaf-out in our forests. Our research group is working with Eli Melaas to provide field observations of plants, in order to help verify the maps made using remote sensing data.

In this map of the Allandale Woods in the Jamaica Plain area of Boston, the average leaf-out times are shown, with the red indicating early leaf-out and the light tan indicating later leaf-out. Areas shown in green are lawns, fields, and other areas not occupied by trees (these areas were excluded from the phenology maps). We will be monitoring leaf-out times once a week along a transect through the Allandale Woods that ranges from early leaf-out to late leaf-out, during the spring season. We will also monitor several other transects that span the range of early to late leaf-out, around the Boston area.

Above, Richard Primack and Lucy Zipf observe the phenology of an urban tree at Bellevue Hill, while Eli Melaas marks the GPS point to later map the tree with its phenology 

Will leaf-out times on the ground correspond to leaf-out times using remote sensing data? Are different leaf-out times due to microsite differences in temperature, different species of trees in each location, or different shrub understory? Stay tuned to find out!