Research Foci
We use remote sensing, in-situ measurements, and biogeophyical models to study local, regional, and global patterns and processes related to land cover and ecosytem properties that affect water, carbon and energy fluxes between the land surface and the atmosphere. We are especially interested in characterizing how terrestrial ecosystems are changing, and how these changes affect the climate system. Current investigations are organized into three broad and interrelated scientific focus areas:
Land Cover Science
Land cover and land cover change research in our group currently focuses on two main themes. First, we are responsible for maintaining and refining the MODIS Land Cover Type Product (MCD12Q1). This product includes a set of five layers in which land cover is mapped using different classification systems including the International Geosphere-Biosphere Programme classification, a 14-class system developed at the University of Maryland, a 6-biome system used by the MODIS LAI/FPAR algorithm, a biome classification developed by scientists at the University of Montana in support of ecosystems models, and a plant functional type classification designed to support land surface parameterizations in climate models. The most recent version of this product is collection 6, which is described in Sulla-Menashe et al. (in preparation).
The second main element of current land cover-related research focuses on monitoring change in global land cover. The goal of this work is to develop new methods and algorithms that make more effective and explicit use of time series information and techniques. This work specifically attempts to exploit the 11+ year time series of MODIS data using Bayesian and functional data analysis techniques to detect and characterize signatures of land cover change in MODIS time series. A central challenge of this work is to develop robust techniques that are suitable for use with moderate and higher spatial resolution data, and that are able to capture the wide range of processes (including both natural disturbance and human-induced land cover change) that produce change at global scales. Research activities in this area have strong overlap with our activities focused on human-dominated ecosystems.
Phenology and Climate
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 .
Human Dominated Ecosystems
Agriculture is far-and-away the most extensive land use on planet Earth. Urban areas occupy a very small portion of the Earth’s total land area, but have a disproportionate effect on the global environment. The impacts of cities and agriculture include greenhouse gas emissions, human appropriation of net primary productivity, hypoxic zones in the oceans from fertilizer runoff, increasing soil salinity caused by irrigation, and urban heat islands, to name only a few. Further, both types of land use have tremendous importance to society. Over 50% of the Earth’s population now lives in cities and agricultural land will need to produce more food in the coming decades to support a growing global population. Urban and agricultural systems are both threatened by climate change related changes in the Earth system. We use remote sensing to quantify and characterize patterns of land use and
land cover change at a sub-continental scale to better understand anthropogenic and climatic
impacts across South America’s Southern Cone. One major component of the project is to identify crop species (e.g., maize, soybeans) at the field level using Landsat and Sentinel imagery. Another component of the project is to estimate proportion of herbaceous and woody vegetation across Southern Cone pasturelands, monitoring for desertification and woody encroachment.
For information related to ongoing funding and projects, please click on the “Current Projects” link in the menu at the top of this page.