Abnormal shoot growth in Korean red pine as a response to microclimate changes due to urbanization in Korea.

Impacts of climate change (e.g., abnormal growth in plants, early flowering, and shifting vegetation zones) are being detected throughout the world. Urban land use and its resulting microclimates work in conjunction with the impacts of climate change. Among the principal environmental signals that modulate bud flush, only temperature has changed significantly in recent years. Throughout South Korea, abnormal shoots (usually known as lammas shoots) in Korean red pine (Pinus densiflora), which were once a rare phenomenon, have become notably more common in recent years. The phenomenon is prominent in urban site of each local area. These abnormal shoots appear at a higher frequency and grow to longer lengths in Seoul's hotter urban center than in suburban sites and showed a close positive correlation with urban density and a close negative correlation with vegetation cover expressed as NDVI. Differences in temperature among the urban center, urban edge, and suburban greenbelt were significantly correlated with land-use intensity. Korean red pines planted in urban parks at sites in urban centers showed a lower frequency of abnormal shoots, and the length of the shoots was shorter, compared with those at the other urban sites. Furthermore, the phenology of Korean red pines in an urban park with a fountain showed a spatial difference, depending upon the distance from the fountain: pine trees close to the fountain did not produce abnormal shoots, but abnormal shoot growth increased with the distance from the fountain. These results are noteworthy because they are related to the cooling effects of evapotranspiration from vegetated landscapes and evaporation from a water body. From the results of this study, we could confirm that microclimate change due to urbanization accelerates the impacts of climate change on plant phenology. Furthermore, we identified the possibility that judicious land-use planning could contribute to minimizing the adverse effects of climate change.