Modeling future invasion of three non-native grasses and their effects on native species in semiarid lands

The effects of non-native, invasive grasses have been studied for decades, yet the implications that these introductions might have for future terrestrial ecosystems are just beginning to be observed and understood. To understand the effects that possible range expansions of three non-native grasses might have on present and future ecosystems in Texas and Puerto Rico, I designed and conducted three modeling exercises, one field experiment and one greenhouse experiment. Results showed substantial potential range expansion for Eragrostis lehmanniana and Nassella tenuissima and some modest increases for Cenchrus ciliaris in Texas; range expansion for C. ciliaris in Puerto Rico was restricted but raises concerns for offshore islands of conservation value. Soil nutrient assessment for C. ciliaris plots showed limited differences between treatments for sites in Texas and Puerto Rico. In Puerto Rico, native patches had more nitrogen in the Guánica Forest samples, while in Texas native plots in Big Bend NP had a higher pH than C. ciliaris plots, in Laguna Atascosa NWR native plots had larger values for sodium. Greenhouse competition experiments showed that the presence of the non-native grasses tended to negatively affect native plant survivorship, biomass production and nutrient allocation with increasing non-native density in the study pots. Results show that management of these grasses should be taken seriously and detected early on to minimize lasting ecosystem effects in conservation areas and active management in rangelands to optimize forage quality.

Embargo status: Restricted until 06/2024. To request the author grant access, click on the PDF link to the left.