Threshold depth for girdling-induced mortality in Eucalyptus camaldulensis: a predictive approach for invasive species management.

Invasive species, such as Eucalyptus camaldulensis, pose significant ecological challenges in protected areas worldwide due to their environmental impacts and complex management. This study aimed to determine the threshold depth of girdling necessary to induce mortality in E. camaldulensis and to develop a predictive model for its practical application in invasive species management. Two populations of E. camaldulensis girdled in 2010 and 2017, along with a control group, were monitored for survival, decline, and phenological responses over one year. Survival analysis using Kaplan-Meier and Cox proportional hazards models revealed that girdling depth was the most significant factor affecting tree mortality, with a critical threshold of 6.55 cm. Trees girdled below this depth showed significantly higher survival rates. A positive linear relationship was identified between tree breast height circumference, and the minimum girdling depth required for mortality, enabling the development of a predictive model. Girdled trees exhibited a significant reduction in fruit and young leaf production, along with an increase in mature leaves and tree decline, compared to control trees. These findings provide a science-based and sustainable approach for managing E. camaldulensis populations in protected areas. The proposed model offers a practical tool for estimating the necessary girdling depth based on tree size, minimizing the use of chemical inputs and promoting adaptive management. This approach ensures targeted and efficient control of this invasive species, enhancing the conservation of native ecosystems.