Electronic Journal of Differential Equations, Vol. 2012 (2012), No. 237, pp. 1-18. Title: Optimal control applied to native-invasive species competition via a PDE model Authors: Wandi Ding (Middle Tennessee State Univ., Murfreesboro, TN, USA) Volodymyr Hrynkiv (Univ. of Houston - Downtown, Houston, TX, USA) Xiaoyu Mu (Univ. of Tennessee, Knoxville, TN, USA) Abstract: We consider an optimal control problem of a system of parabolic partial differential equations modelling the competition between an invasive and a native species. The motivating example is cottonwood-salt cedar competition, where the effect of disturbance in the system (such as flooding) is taken to be a control variable. Flooding being detrimental at low and high levels, and advantageous at medium levels led us to consider the quadratic growth function of the control. The objective is to maximize the native species and minimize the invasive species while minimizing the cost of implementing the control. An existence result for an optimal control is given. Numerical examples are presented to illustrate the results. Submitted September 5, 2012. Published December 26, 2012. Math Subject Classifications: 49J20, 34K35, 92D25. Key Words: Optimal control; partial differential equations; native-invasive species; salt cedar; cottonwood; spatial models.