Dr. Eli Melaas, postdoctoral scholar at the Department of Earth and Environment, Boston University gave an invited talk at American Geophysical Union 2016 about his work connecting urban heat islands to changes in tree leaf cycles (unfolding and coloring). Here is a portion of what he recently shared with NASA:
What are the major findings of this research? Results from this research show that a strong coupling exists between the surface urban heat island of Boston and the timing of spring leaf unfolding and autumn coloring of vegetation at both landscape and regional scales. On average, spring occurs 1.8 days earlier and autumn 2 days later for each 1 °C (1.8F) increase in mean growing season temperature. However, the spring phenology of urban woodland patches (largely consisting of native tree species) was less sensitive to urbanization.
What are the implications of your findings? Urban heat islands serve as a sort of proxy for climate change and, therefore, provide insight as to how plants may behave under future warming. Our results indicate that the advancement of spring phenology of temperate deciduous forests may be less than what has been previously suggested by studies using satellite remote sensing data.
Can you describe how the presence of exotic tree species may affect the phenology/temperature relationship? Previous research has demonstrated that exotic tree species (e.g., Norway maple) leaf out significantly earlier than native tree species in spring. Since surrounding rural areas are mainly composed of native species, it is important to accurately map native species within urban areas in order to appropriately assess the impact of elevated urban temperatures on phenology.—The original NASA item.
Environmental Research Letters
January 3, 2017 NewTerrain.