Detecting Tamarisk beetle induced defoliation and vegetation regrowth in Colorado River Tributary with Landsat time series

Keywords: Tamarisk beetles, Saltcedar, Time Series
Abstract Type: Paper Abstract

Abstract

The Tamarisk beetle was introduced as a biological control agent to reduce saltcedar (Tamarix spp.) populations. Although the field release of beetles was discontinued, they continue to spread along the Colorado River tributary. Tamarisk beetles typically take 3–5 years to defoliate saltcedar. However, the timing of beetle-induced defoliation and the subsequent regrowth of vegetation varies by location and is challenging to predict. To address this, we developed a framework to detect defoliation and vegetation regrowth driven by Tamarisk beetles along the Colorado River tributary. First, we trained a deep learning model using time series data from 2001 to 2022, combining all available Landsat imagery to detect various types of land disturbance. Next, we fine-tuned the model for beetle-observed sites along the tributary, focusing on changes in NDVI to identify specific disturbance patterns. Our results provide a reference on the impact of Tamarisk beetles on saltcedar and support planning for further vegetation conservation and restoration.