Detect the time of Tamarix defoliation at Colorado River in Arizona

Keywords: Tamarix, COLD, vegetation regrowth, timing
Abstract Type: Paper Abstract

Abstract

Tamarix is a widely spread invasive plant in southwestern United States. Tamarix reduced soil evapotranspiration, increased water consumption, soil salinity, fire possibility, floods and erosions. To control Tamarix, Diorhabda (Northern tamarisk beetle) was introduced and released in the field from 2001 to 2010. However, the success of controlling Tamarix is inconsistent as discussed in many studies. Vegetation indices did not decrease at some locations after the biocontrol program. Yet at other locations, those indices decreased in three to five years after the program and then started to increase afterwards. Therefore, in this study, we apply the COntinuous monitoring of Land Disturbance (COLD) model to detect the timing of Tamarix defoliation and vegetation regrowth at the Diorhabda observed and surrounding areas along Colorado River in Arizona with the 30m fusion products of MODIS and Landsat data. The plant communities along the Colorado River have been heavily invaded by Tamarix and intensive efforts have been made to control the invasive Tamarix with multiple releases of Diorhabda during the biocontrol program. The COLD model detects land disturbance in a near real-time manner. After model initialization, COLD will detect land disturbance with consecutive observed values that are out of an expected range. The detected defoliation and vegetation regrowth timing will provide important indication of the success of biocontrol program.