Native Plant Allelopathy: A Potential Approach to Limit Invasive Grass Encroachment in Thorn Forest Restoration

Less than 5% of the Tamaulipan thorn forest remains in the United States. For this reason, there have been many attempts at restoration of this ecosystem. Oftentimes these attempts are unsuccessful due to the high prevalence of invasive African grasses that outcompete the seedlings. In an effort to improve the efficacy of these restoration efforts, native plant allelopathy has been examined for its ability to exclude invasive guineagrass. Native species were surveyed and selected species were tested for allelopathy in laboratory bioassays. The species that exhibited allelopathy in the laboratory were then evaluated in pot experiments for their ability to reduce fungal infection in guineagrass roots, grass stem mortality, and grass growth, and in the field as mulch for their ability to reduce guineagrass cover and growth. There were several potentially allelopathic species identified, stem mortality was increased by E. ebano, V. schaffneri, and Z. fagara. The mulch of Z. fagara almost entirely excluded invasive grass growth and mulch from E. anacua and V. schaffneri reduced invasive grass growth. These experiments suggest that mulch from Z. fagara could be very useful in restoration due to its ability to prevent guineagrass growth