2010 Tropical dry forest height and foliage height profiles mapped with Landsat and ALI image time series

Forest age, vertical structure, disturbance history, and species composition are related forest attributes that affect avian habitat.  For studies of wintering habitat for the endangered Kirtland’s Warbler, scientists from IITF and collaborators showed for the first time that forest vertical structure can be mapped with a time series of satellite imagery.  They mapped forest height, height variance, and foliage height profiles on the island of Eleuthera , The Bahamas. They also provided the first example of simultaneously mapping forest age and disturbance type with an image time series in which the each time step in the image sequence is a mosaic of the cloud-free parts of many scenes.  The information proved invaluable for characterizing this species’ wintering habitat and for providing the first estimates of forest disturbance rates by disturbance type.

Remote sensing of forest vertical structure is also possible with lidar data, but lidar data that cover landscapes are rare and expensive.  In contrast, the types of imagery that this study used are widely and freely available, including Landsat imagery dated from 1984 to 2002 and Advanced Land Imagery (ALI) data from around 2005.  The ALI data are the precursor to the Landsat Data Continuity Mission that will launch in December of 2012.  The study also indicated that these newer images will improve our ability to map forest structure with satellite data.  The entire time series of images were critical to accurately mapping forest vertical structure, however.  After forest disturbance young forest spectral responses change as they grow taller and denser. Consequently, the scientists reasoned that the pattern of spectral responses over time should be related to forest height.

The article is published in Remote Sensing of Environment (http://www.sciencedirect.com/science/journal/00344257) and is a contribution to the Landsat Science Team and the Landsat Data Continuity Mission (http://landsat.usgs.gov/ and http://ldcm.nasa.gov/).