Under the background of global warming, phenology study can not only examine terrestrial ecosystem response to climate change, but also provide the more accurate input parameters for climate-carbon cycle models. With global urban expansion on the Earth's surface, the study of urban phenology will be an important research sub-area related to carbon cycle, urban heat island effect, and human health issues studies. This study is focused on intensive phenological observation and analysis in an urban woodlot on the University of Wisconsin-Milwaukee campus. We launched a general observation program in spring 2007 and detailed phenological observations in fall 2007. Moderate resolution remotely sensed (MODIS) data is used to determine the onset of spring and the end of fall, while high resolution remotely sensed data (LANDSAT 7, ASTER, and QUICKBIRD) is used to examine the detailed corresponding phenophases on several specific dates. Air and soil temperatures recorded by four HOBO sensors in the study area are employed to detect the climate change effect.
Results/Conclusions In this study, we expect to reach the preliminary results of understanding the primary characteristics of urban phenology, and the detailed relationship between urban phenology and the climatic factors. The preliminary study results show that the phenological events of understory take place a little earlier than those of trees in spring. Two dominant individual species, white ash and basswood, represent the noticeable difference on the changes of phenological events in fall. White ash showed a gradual variation in both leaves colored and leaves fallen, while basswood shows a slow, rapid, and then slow change in these two phenological events. Therefore, the whole community mainly composed by these two dominant tree species showed an integrative trend, growing relatively quickly and then slowly. To some extent, we can assume that photoperiod may be the crucial factor influencing the leaves coloring and falling of white ash. On the contrast, the fall phenophases of basswood may be significantly influenced by temperature. The Landsat NDVI values corresponded well to the phenological change of vegetation on the ground in fall. However, it is probably raised by the questionable remote sensing data that the Landsat NDVI values did not match the change of plant phenology in spring. For the fall observation, there is no obvious spatial correlation between the NDVI values and the phenological events in the study area.
