Using Remote Sensing to Track Invasive Trees
By Ann Perry
May 21, 2010
A team of
Agricultural Research Service (ARS)
scientists has refined remote sensing tools for identifying invasive Ashe
juniper shrubs and trees in central Texas and nearby regions. These findings
can help rangeland managers determine the extent and severity of Ashe juniper
infestations and boost mitigation efforts.
Over the past century, the expansion of Ashe juniper has reduced the
production and diversity of other rangeland plant species. Because Ashe juniper
has little nutritional value for grazing animals, the vegetative shift has also
reduced forage options for livestock and wildlife.
ARS agricultural engineer
Yang and rangeland scientist James Everitt evaluated remotely sensed data
to pinpoint the most accurate signal for identifying Ashe juniper
stands, which often grow within an assortment of other woodland plants. Yang
and Everitt work at the ARS
de la Garza Subtropical Agricultural Research Center in Weslaco, Texas.
Remotely sensed data were collected from two Texas sites that were populated
with Ashe juniper and other associated plant communities. The data spanned 98
spectral bandswhich are bands of light that are characterized by
different wavelengthsthat ranged from 475 to 845 nanometers.
Then the team used a statistical technique called minimum noise fraction
(MNF) transformation to reduce interference. In comparison with the original
imagery, MNF imagery takes less time to process and less data space to store,
especially when large amounts of remotely sensed data are being analyzed.
MNF transformation consolidated the spectral data into 50 distinct bands.
Further analysis indicated that the first 10 bands from this group were the
best for identifying Ashe juniper stands. Using these bands, the scientists
were able to sufficiently distinguish Ashe juniper from other mixed woody
species, other mixed herbaceous species, bare soil and water.
Results from this work were published in the International
Journal of Remote Sensing.
ARS is the principal intramural scientific research agency of the
U.S. Department of Agriculture.