Phenology in urban heat islands

A study suggests how warming conditions are likely to affect plant phenology. Air temperatures in cities tend to be warmer than in rural surroundings. Hence, cities can be used as natural laboratories for studying the ecological effects of climate warming. How phenology, or the timing of recurring events in plants’ life cycles, differs between urban and rural environments, and the extent to which temperature contributes to this difference, remain unclear. Jiafu Mao, Yuyu Zhou, and colleagues examined changes in the start of plants’ greening season (SOS), derived from satellite data, in 85 cities with urban areas larger than 500 km2 in the coterminous United States from 2001 to 2014. SOS occurred 6 days earlier on average in most urban areas than in corresponding rural areas. However, the rate of SOS advancement with preseason mean air temperature was weaker on average in urban areas compared with rural areas. The reduced advancement rate mostly occurred in relatively cold regions, such as the northeastern and upper Midwestern United States; the magnitude of the urban-rural difference in both SOS and advancement rate mainly correlated with the urban-rural temperature difference. The results suggest that phenological responses to temperature become weaker under warming. Further, although the onset of spring phenology may continue to advance under future warming, the rate of advancement will likely slow down as warming continues, according to the authors.

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Article #19-11117: “Urban warming advances spring phenology but reduces the response of phenology to temperature in the conterminous United States,” by Lin Meng et al.

MEDIA CONTACT: Jiafu Mao, Oak Ridge National Laboratory, TN; tel: 865-804-5605, 865-576-7815; e-mail: <

[email protected]

>; Yuyu Zhou, Iowa State University, Ames, IA; tel: 515-294-2842; e-mail: <

[email protected]

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