This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: For devout leaf peepers, timing is everything. A new study led by researchers from Duke University's Nicholas School of the Environment shows that leaf nutrient levels affect the onset of fall color.
The findings, published in Nature Communications, could improve leaf drop forecasts and carbon cycle tracking. Starting roughly in September in the United States, deciduous trees—species that seasonally drop their leaves—stop making the green pigment chlorophyll, used in photosynthesis. As other pigments become visible, leaves shift to shades of turmeric and crimson before dropping off.
By mid-November, most deciduous trees are bare. That process, called senescence, is a tree's way of conserving energy for winter. As days shorten, less sunlight is available to leaves to convert carbon dioxide from the air into life-sustaining sugars.
Photosynthesis, which is energy-intensive, basically becomes more trouble than it's worth for several months. Although trees in a given locale start changing color at roughly the same time each year, environmental factors such as temperature and rainfall can affect autumn leaf senescence. For example, more rain during autumn can extend how long leaves cling to trees.
Nutrients in leaves also play a role in senescence. For instance, the elements nitrogen, phosphorus and potassium regulate critical leaf processes, including chlorophyll production and the transport and use of sugars. Those same nutrients are also important components of fertilizers used on crops.
Their release into the environment could disrupt the balance of nutrients in leaves and therefore alter the timing of senescence, according to Tong Qiu, assistant professor of ecology at the Nicholas School, who oversaw the new study. However, measuring nutrient levels in leaves has traditionally been labor-intensive and expensive, inhibiting evidence-based research on autumn senescence. "Usually, measuring nutrients requires people to collect leaves and go back to the lab and do an experiment to quantify their concentrations," Qiu says.
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