In Fall, 2002, we started a project to understand the invasive potential of Ailanthus altissima, a tree becoming known to us as 'Tree of Almost Heaven' (with apologies to John Denver). This work is funded by two major grants from the USDA (2002-2005) and NASA (2004; ongoing). I am increasingly being willing to stick my neck out and claim that Ailanthus may be the most serious invasive tree species threat to the esatern deciduous forest, both economically and ecologically. There are several objectives this research, including (a) quantifying short- and long-distance dispersal across the landscape, (b) developing remote sensing and image processing techniques to differentiate female and non-female Ailanthus from aerial imagery, (c) studying the present distribution of Ailanthus across the landscape using GIS in combination with vehicular and airborne geopositioning, (d) comparing the germination and establishment of Ailanthus in the forest compared with native colonizing species.

Colleague Tim Warner in the Department of Geography is working on the remote-sensing and image-processing elements of this work. Postdoctoral Associate Rick Landenberger is using his extensive experience in studies of edge species population dynamics to advantage in overseeing all project objectives. Masters student Nathan Kota’s work focuses on the comparative elements of dispersal and establishment for Ailanthus and native tulip poplar (Liriodendron tulipifera). We are beginning to work on a much larger project to quantify how different management trajectories for this one species would impact several classes of ecosystem services over the next century. Economists, social scientists and behavioral scientists, working alongside ecologists, geographers and foresters, would be needed to address this larger question.

Ailanthus stand near Morgantown, WV (far left). Birds' eye view of female Ailanthus from Piper Apache (left).

The Ailanthus project is an extension of my lab's long-term interest in using remote sensing as a way of remote censusing: literally collection of data for population projection matrix models using the tools of remote sensing and image processing. Working closely with Dr. Tim Warner (Dept. of Geology and Geography), we attended conferences and obtained seed grants beginning six years ago to explore the possibilities. Encouraged by the response, we wrote a major grant to NSF and were funded in full to work on the computational aspects of distinguishing tree species and individuals from aerial imagery. This research resulted in several publications, particularly with postdoctoral research associates, Rick Landenberger and Tomas Brandtberg.

Twin-engine Piper Apache aircraft used for digital imagery acquisition by forest remote sensing project (far left). Collaborator Dr. Timothy Warner preparing GPS system for takeoff.

In December, 2003, Rob Lamar completed his Ph.D work under my direction on the same issues with studies of hemlock in Shenandoah National Park. In the study area, hemlock is rapidly dying due to the introduced pest, hemlock woolly adelgid. We believe remote sensing can be used to spatially map hemlock mortality over a large scale, thus improving our understanding of why hemlock dies rapidly in some areas but not in others when hit by adelgid outbreaks.

	Winter aerial photograph of hemlock stand (partial photo) showing living individual trees.
	Same image after image processing using watershed segmentation algorithm developed by Rob Lamar

The exciting prospects for the methodological advances possible in a marriage of plant population biology with remote sensing fall into two classes: (1) detection of rare individuals or communities, and (2) detection of large-scale change in common elements of the forest. Detection of rare individuals could be invaluable in terms of both conservation of rare species and restoring now-rare species to their former prominence. For example, we have been investigating whether there are spectral signatures of American chestnut. While they were once one of the most common (and valuable) of all eastern deciduous forest trees, the exotic chestnut blight obliterated this species earlier in this century. Nevertheless, occasional large individuals remain in the forest, although any given forester is likely to have encountered only one or two in their lifetimes. Are these rare individuals there because of chance? Or, could they be genetically resistant to the blight? If genetic resistance is rare, the only way to find it would be by screening large numbers of individual trees. What is the best way to prospect for large numbers of a rare item in the forest canopy? Remote sensing. The chestnut is just one example of potential applications of bioprospecting. Detection of rare ‘pest’ or ‘exotic’ species, such as Ailanthus, is another application with potentially huge payoffs in terms of conservation – detecting invasions before they are out of control. See my link to conservation and remote sensing for a description of an application to conservation biology.

At the other end of the rarity scale are common species that are undergoing shifts in abundance due to many possible factors. Global climate change, for example, will have subtle effects over long periods of time. Detecting effects of such change on the forest requires scaling up the censusing of populations to the regional level.

All of this research is timely because it comes on the eve of high spatial resolution satellite remote sensing in the commercial sector. Developing the potential to make maximum use of such data now will position us to take advantage of this capability as it becomes available.