According to a new study by researchers at Princeton University, trees located in the continental United States could send out new spring leaves up to 17 days earlier in the coming century than they did before temperatures around the world began to rise. These climate-driven changes could also lead to changes in the composition of the northeastern forests, as well as give a boost to their ability to take up carbon dioxide.
Because trees play an important role is taking up carbon dioxide from the atmosphere, researchers wanted to evaluate predictions of spring budburst, which is when deciduous trees push out new growth after months of winter dormancy, from models that predict how carbon emissions will impact global temperatures.
The date of budburst affects how much CO2 is taken up each year. However, most climate models to date have used overly simplistic schemes for representing spring budburst. For example, most climate models use a single species of tree to represent all trees in a geographic region.
The Princeton team of researchers, which was led by David Medvigy, an assistant professor in Princeton's department of geosciences, published a new model relying on warming temperatures and the waning number of cold days to predict spring budburst. The model proved accurate when compared to actual data on budburst in the northeastern United States. This model was published in 2012 in the Journal of Geophysical Research.
In the current paper, which was published online in the Geophysical Research Letters, Medvigy and his team tested the model against a broader set of observations collected by the USA National Phenology Network, which is a nation-wide tree ecology monitoring network that consists of federal agencies, federal institutions, and citizen scientists.
The team used the 2012 model to make predictions of future budbursts based on four possible climate scenarios used in planning exercises by the Intergovernmental Panel on Climate Change. They estimated that compared to the late 20th century, red maple budburst will occur 8 to 40 days earlier, depending on the part of the country, by the year 2100. They also found that the northern parts of the U.S. will have more pronounced changes than the southern portions, with the biggest changes going on in Maine, New York, Michigan, and Wisconsin.