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Remote Sens. 2016, 8(7), 524;

Mapping Presence and Predicting Phenological Status of Invasive Buffelgrass in Southern Arizona Using MODIS, Climate and Citizen Science Observation Data

Western Geographic Science Center, U.S. Geological Survey, Tucson, AZ 85719, USA
Agricultural Research Station, U.S. Department of Agriculture, Tucson, AZ 85719, USA
Southern Arizona Buffelgrass Coordination Center, Tucson, AZ 85717, USA
USA National Phenology Network, U.S. Geological Survey, Tucson, AZ 85721, USA
Arizona Water Science Center, Tucson, AZ 85719, USA
Author to whom correspondence should be addressed.
Academic Editors: Yoshio Inoue and Prasad S. Thenkabail
Received: 25 February 2016 / Revised: 11 May 2016 / Accepted: 31 May 2016 / Published: 24 June 2016
(This article belongs to the Special Issue Citizen Science and Earth Observation)
PDF [6387 KB, uploaded 30 June 2016]


The increasing spread and abundance of an invasive perennial grass, buffelgrass (Pennisetum ciliare), represents a critical threat to the native vegetation communities of the Sonoran desert in southern Arizona, USA, where buffelgrass eradication is a high priority for resource managers. Herbicidal treatment of buffelgrass is most effective when the vegetation is actively growing, but the remoteness of infestations and the erratic timing and length of the species’ growth periods confound effective treatment. The goal of our research is to promote buffelgrass management by using remote sensing data to detect where the invasive plants are located and when they are photosynthetically active. We integrated citizen scientist observations of buffelgrass phenology in the Tucson, Arizona area with PRISM precipitation data, eight-day composites of 250-m Moderate-resolution Imaging Spectroradiometer (MODIS) satellite imagery, and aerially-mapped polygons of buffelgrass presence to understand dynamics and relationships between precipitation and the timing and amount of buffelgrass greenness from 2011 to 2013. Our results show that buffelgrass responds quickly to antecedent rainfall: in pixels containing buffelgrass, higher correlations (R2 > 0.5) typically occur after two cumulative eight-day periods of rain, whereas in pixels dominated by native vegetation, four prior 8-day periods are required to reach that threshold. Using the new suite of phenometrics introduced here—Climate Landscape Response metrics—we accurately predicted the location of 49% to 55% of buffelgrass patches in Saguaro National Park. These metrics and the suggested guidelines for their use can be employed by resource managers to treat buffelgrass during optimal time periods. View Full-Text
Keywords: buffelgrass; MODIS-NDVI; PRISM; phenology; correlation phenometrics; invasive species buffelgrass; MODIS-NDVI; PRISM; phenology; correlation phenometrics; invasive species

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Wallace, C.S.A.; Walker, J.J.; Skirvin, S.M.; Patrick-Birdwell, C.; Weltzin, J.F.; Raichle, H. Mapping Presence and Predicting Phenological Status of Invasive Buffelgrass in Southern Arizona Using MODIS, Climate and Citizen Science Observation Data. Remote Sens. 2016, 8, 524.

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