Identifying allelopathic native plants for use in thorn forest restoration

Emily A Mullins, Graduate Student Oral Presentation

Authors: Mullins, E., Fierro Cabo, A

Affiliation University of Texas Rio Grande Valley

The Tamaulipan thorn-forest is composed of species well adapted to semi-arid environments and is one of the most biodiverse regions in North America. This biome has been affected by extensive deforestation for agriculture, grazing, and urban development, resulting in a loss of over 95% of the original thorn-forest habitat. Most relevant restoration efforts are being undertaken by US Fish and Wildlife Service, Texas Parks and Wildlife Department, and The Nature Conservancy of Texas, and involve reforestation of abandoned fields frequently invaded by African grasses

Restoration efforts have been hindered by the presence of invasive grasses with the ability to outcompete seedlings for resources such as light, water, and nutrients. The “novel weapons” hypothesis suggests that some invasive species are very successful in new environments due to allelopathic compounds that native species me not adapted to tolerate. It is possible that this effect can be reciprocal, the “homeland security” hypothesis proposes that invasive species may be susceptible to allelochemicals produced by native species

To identify potentially allelopathic native plants, field surveys and laboratory bioassays were performed. Based on field observations, aqueous extracts and dilutions were prepared from dried leaf material of woody and herbaceous native plants selected from the Tamaulipan thorn forest. Extracts from several of these species slowed germination rates up to 78 percent and reduced seedling elongation by up to 47mm in bioassay experiments.

Research is part of The Nature Conservancy’s Sabal Palm/Thornscrub Research Project funded by the Robert J. Kleberg, Jr. and Helen C. Kleberg Foundation.  For further information, contact Sonia Najera at