Southern Arizona Ecological Forecasting – NASA DEVELOP Fall 2016 @ Jet Propulsion Laboratory

Southern Arizona Ecological Forecasting – NASA DEVELOP Fall 2016 @ Jet Propulsion Laboratory


>>ERIKA: Buffelgrass, or Pennisetum ciliare,
is a perennial bunchgrass that is originally from Africa, the Middle East, Asia and Europe. Despite its unintimidating name, buffelgrass
is an aggressive invasive species that has expanded across the southwestern United States
threatening urban settings and the native landscapes of the Sonoran Desert.>>CINDY: Typically, in the Sonoran Desert,
when you have a very natural landscape you’ll see a lot of spaces between plants. So if
lightning strikes and a fire starts it just burns up right there and doesn’t travel. But with this [buffelgrass] in the landscape,
it can carry the fire broadly. And a lot of these plants are not adapted
to fires.>>ERIKA: Currently, the NPS has been monitoring
the spread of buffelgrass through an expensive combination of of aerial and ground surveys. Efforts to eradicate buffelgrass have been
manual or through the application of herbicides. Herbicidal treatments, however, must be applied
when the plants are at least 50% photosynthetically active. The objective of this project was to improve
the capacity of the NPS to both detect and plan eradication efforts of buffelgrass
through NASA Earth Observations. The Southern Arizona Ecological Forecasting
team at JPL partnered with the US Geological Survey, Northern
Arizona University, and the National Park Service. Together, we looked at how to detect
buffelgrass presence in Organ Pipe Cactus National Monument in southwestern Arizona.>>NICK: The team acquired Normalized Difference
Vegetation Index or NDVI, Gross Primary Productivity, and Evapotranspiration data from the
MODIS sensor onboard Terra. High spatial resolution Imagery was also downloaded
from the commercial satellite WorldView-2. Precipitation
data was obtained from the PRISM Climate Group, and spectral data for buffelgrass was provided
by one of our project partners.>>MOLLY: The team evaluated two methods for
buffelgrass detection. The first used the Climate Landscape Response
or CLaRe metrics developed by Cynthia Wallace et al to predict buffelgrass
presence based on pixelwise correlation values between NDVI and Change in NDVI with different
accumulation periods of precipitation. We also investigated correlations with evapotranspiration
and water use efficiency. T-Tests were
performed to analyze whether correlations values at pixels with known buffelgrass presence
were statistically different from those where presence was unknown. A generalized linear model was also developed
to detect a probability threshold that could be used by land managers to
inform what specific correlation value indicate in terms of presence or absence of buffelgrass.>>NATALIE: We also tried a spectral-based
approach. Different types of land cover have different
levels of reflectance across the varying wavelengths of the electromagnetic spectrum. This is known as the spectral signature. We used a target detection method called Mixture
Tuned Matched Filtering, or MTMF, to measure the
occurrence of the buffelgrass spectra across the WorldView-2 images. MTMF produces two outputs
–the Matched Filter score, which represents the percent land cover of the buffelgrass
spectra, and an Infeasibility Value, which indicates
the likelihood of a false positive. High matched filter scores and low infeasibility
values are more likely to represent the target. We then
used these pixels to create a classification map of buffelgrass presence.>>ERIKA: By investigating the dynamics of
the landscape, this work will help park managers track the growth of buffelgrass within their
parks and plan eradication efforts to preserve the
native ecosystems of the southwest.

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