Response of vegetation phenology to urbanization in the conterminous United States

Abstract

The influence of urbanization on vegetation phenology is gaining considerable attention due to its implications for human health, cycling of carbon and other nutrients in Earth system. In this study, we examined the relationship between change in vegetation phenology and urban size, an indicator of urbanization, for the conterminous United States. We studied more than 4500 urban clusters of varying size to determine the impact of urbanization on plant phenology, with the aids of remotely sensed observations since 2003-2012. We found that phenology cycle (changes in vegetation greenness) in urban areas starts earlier (start of season, SOS) and ends later (end of season, EOS), resulting in a longer growing season length (GSL), when compared to the respective surrounding urban areas. The average difference of GSL between urban and rural areas over all vegetation types, considered in this study, is about 9 days. Also, the extended GSL in urban area is consistent among different climate zones in the United States, whereas their magnitudes are varying across regions. We found that a tenfold increase in urban size could result in an earlier SOS of about 1.3 days and a later EOS of around 2.4 days. As a result, the GSL could be extended by approximately 3.6 days with a range of 1.6-6.5 days for 25th ~ 75th quantiles, with a median value of about 2.1 days. For different vegetation types, the phenology response to urbanization, as defined by GSL, ranges from 1 to 4 days. The quantitative relationship between phenology and urbanization is of great use for developing improved models of vegetation phenology dynamics under future urbanization, and for developing change indicators to assess the impacts of urbanization on vegetation phenology.

Enhanced Vegetation Growth in the Urban Environment Across 32 Cities in the Northern Hemisphere

“…We found that the urban environment leads to advanced SOS, delayed EOS, and extended GSL, but the situations vary drastically across regions in the Northern Hemisphere. In the north of East Asia and the east of North American, our results are consistent with those in Zhou et al () and Li et al (). In addition to satellite observations, we include analysis on ground‐based data in the region of North America.…”

“…Because both vegetation SOS and EOS are obtained using the same method, the systematic errors in calculating the differences between urban and rural vegetation phenological dates could be effectively eliminated. Most existing studies did not try to evaluate vegetation phenology metrics derived from remote sensing data due to data availability (Li et al, ; Zhou et al, ); it is obviously an important issue to validate satellite‐derived vegetation phenology with field observations when sufficient data become available, but there is a need to account for the scaling factor that results in differences between remote sensing and ground‐based observations.…”

“…There remain key issues in understanding how the urban environment impacts the vegetation phenophases. Most studies have found that the start of season (SOS) advanced and the end of season (EOS) delayed in urban areas as compared with those in rural areas when analyzing remote sensing data (Li et al, ; White et al, ; Zhang et al, ; Zhou et al, ) and in situ measurement data (Lu et al, ; Roetzer et al, ). Some studies only found marginal advance or even delay in vegetation SOS in urban areas (Gazal et al, ; Jochner et al, ; Ziello et al, ).…”

Impact of urbanization on abundance and phenology of caterpillars and consequences for breeding in an insectivorous bird

“…), could alter the phenology of each component of the system (Forrest , Li et al. ) and have consequences for demography and population dynamics. In this study, we used data from multiple sites and years to assess if urbanization alters (1) the phenology of a tri‐trophic plant–caterpillar–insectivorous‐bird system, (2) caterpillar abundance, and (3) has resultant impacts on avian reproductive success.…”

“…These impacts are often the result of large-scale alterations in habitat types, but more subtle effects can also arise through urban development altering biotic interactions including those between plants, phytophagous consumers, and their predators (Kozlov et al 2017). Numerous environmental factors associated with towns and cities, including urban heat island effects that can be similar to those of climate change (McCarthy et al 2010), could alter the phenology of each component of the system (Forrest 2016, Li et al 2016) and have consequences for demography and population dynamics. In this study, we used data from multiple sites and years to assess if urbanization alters (1) the phenology of a tri-trophic plant-caterpillar-insectivorous-bird system, (2) caterpillar abundance, and (3) has resultant impacts on avian reproductive success.…”