Vegetation Dynamics: Phenology

Phenological events, such as budburst and leaf abscission, regulate many ecosystem processes and influence biosphere-atmosphere feedbacks in the climate system. Phenology is also an indicator of biological responses to climate change. In recent years, remote sensing has emerged as a key tool used to study phenology at regional to global scales. In the Land Cover and Surface Climate Group, we are involved in two main activities related to remote sensing and modeling of phenology. First, we are responsible for maintaining and refining the MODIS Land Cover Dynamics Product (MCD12Q2), which provides global maps of seven phenological metrics for all ecosystems exhibiting identifiable annual phenology. These metrics include the date of year for: (1) the onset of greenness increase (greenup), (2) the onset of greenness maximum (maturity), (3) the onset of greenness decrease (senescence), and (4) the onset of greenness minimum (dormancy). The three remaining metrics are the growing season minimum, maximum, and summation of modeled daily vegetation index values from MODIS.

Second, with support from the National Science Foundation’s program in Macrosystems Biology and in collaboration with colleagues at Harvard University, the University of New Hampshire, and Washington University in Saint Louis, we are developing data sets to support continental monitoring of phenology at scales that range from individual trees to moderate resolution pixels provided by sensors such as MODIS. As part of this effort we are exploring how observations collected at different scales can be used to (1) increase understanding of how phenology controls land-atmosphere exchanges of carbon, water and energy, and (2) improve models of phenological responses to climate change .