Invasive grasses in South Texas rangelands: historical perspectives and future directions

Abstract

South Texas is home to a high diversity of species due to its location at the confluence of subtropical, desert, and coastal ecoregions. Historical overgrazing of South Texas rangelands transformed the savanna and prairie to a landscape dominated by woody plants and shrubs interspersed with low seral grass species and bare ground. During the first half of the 20th century, exotic grass species, coupled with the application of industrial agricultural practices appeared to be the future of forage production in South Texas and elsewhere. Several of these exotic species, namely King Ranch bluestem [Bothriochloa ischaemum (L.) Keng], Kleberg bluestem [Dichanthium annulatum (Forssk.) Stapf], Angelton bluestem [Dichanthium aristatum (Poir.) C.E. Hubbard], buffelgrass [Pennisetum ciliare (L.) Link], guineagrass [Urochloa maxima (Jacq.) R. Webster], Lehmann lovegrass (Eragrostis lehmanniana Nees), and Bermudagrass [Cynodon dactylon (L.) Pers.], have escaped pasture cultivation. Additionally, the native grass tanglehead [Heteropogon contortus (L.) P. Beauv. ex Roem. & Schult.] has begun displaying invasive behaviors. The monoculture growth habit of these species simplifies vegetation structure, reduces biodiversity, and decreases habitat for many species of wildlife. These grasses also alter natural fire regimes and nutrient cycling. This landscape-level transformation of vegetation composition and structure requires monitoring to quantify and assess the spatial and temporal distributions of invasive species as a basis to inform management practices. Current advances in remote sensing technologies, such as very high spatial resolution coupled with daily satellite imagery and unmanned aerial vehicles, are providing tools for invasive vegetation monitoring. We provide a synthesis of the natural history of these grasses, including their introductions, an overview of remote sensing applications in South Texas, and recommendations for future management practices.

Mitigating buffelgrass invasion through simulated targeted grazing: understanding restoration potential in a variable precipitation regime

“…Buffelgrass, with light grazing or no grazing, can dominate the native plant community, reduce diversity, and be more resilient to herbivory and drought (Wied et al 2020). In a previous study of this system, we showed that targeted grazing effectively reduced height, cover, and buffelgrass' negative impact on the plant community (Rhodes et al 2021).…”

Floristic composition and potential invasiveness of alien herbaceous plant in Western Mexico

“…The considerable biomass produced by this plant also provides large quantities of fuel which propagate fires (Veldman et al, 2009). Its robust and deep root systems and fastgrowing stalks allows it to recover rapidly after fires (Wied et al, 2020). These traits also make it very resistant to eradication efforts, such as mowing and herbicides (Ammondt et al, 2013;Clark et al, 2008).…”

Season of prescribed fire determines grassland restoration outcomes after fire exclusion and overgrazing

“…Bothriochloa ischaemum (King Ranch Bluestem) is another problematic fire-adapted, invasive grass, which is now widespread in central Texas. Because of its high tolerance to grazing and resistance to drought, this perennial C 4 bunchgrass, native to temperate and subtropical Eurasia, was introduced in the early 1900s to serve as livestock forage (Wied et al 2020). Whereas prescribed fires in the winter promote B. ischaemum invasion (Gabbard andFowler 2007, Havill et al 2015), short-term studies suggest that summer fires can reduce B. ischaemum abundance (Simmons et al 2007, Reemts et al 2019.…”