Suppression of native plant by invasives' Verbena brasiliensis' increases with soil fertility.

The Stress Gradient Hypotheses suggests that plants in highly stressful environments compete less aggressively with one another and move more toward facilitation. Verbena Brasiliensis is an invasive perennial plant in Texas that often co-occurs with the native forb Lythrum alatum. Understanding how these plants respond to one another under different precipitation and soil nutrient conditions would be helpful in setting priorities for management of invasive plants, especially in the context of climate change. My research asks the question whether V. brasiliensis is less suppressive of the growth of the native L. alatum under increasing levels of nutrient and water stress. My expectation is that consistent with the Stress Gradient Hypothesis, the suppression of L. alatum growth by V. brasiliensis will be weaker at lower water and nutrient levels.