Theme 1-2: Rangeland/Grassland Ecology--Poster Sessions
Description
Guinea grass (Megathyrsus maximus syn. Panicum maximum) is an important pasture grass that has been introduced pantropically, yet in many cases has escaped cultivation and is invading native rangelands – threatening biodiversity at multiple trophic levels. An increasing challenge of rangeland management is balancing the importance of pasture grasses with their negative impact on ecosystem processes. Given this challenge, it is critical to understand the mechanisms that underlie grass invasion. In this descriptive study, our objective was to assess the ecological stress release hypothesis by comparing the relative abundance and functional traits of Guinea grass in Kenya's home range with its introduced range in Texas, USA. To characterize Guinea grass dominance in Texas vs. Kenya, we measured plant height and cover and examined the associated arthropod and ungulate abundances. We characterized these associations across three habitat types of differing resource availability; 1) Under woody legumes with higher soil moisture and soil nitrogen, 2) grasslands with higher light yet drier soils, 3) riparian areas with higher soil water moisture and light. We found that Texas Guinea grass was 50% taller than Kenyan Guinea grass except for riparian environments comparable to its introduced range. Texan Guinea grass occupied 50% more area than Kenyan Guinea grass and was especially abundant under woody legumes. Texas ungulate communities were less diverse and abundant. The arthropod herbivore diversity was twice as high on Kenyan Guinea grass. These results suggest that Guinea grass has escaped a rich assemblage of herbivores and likely explains some of its spread in nonnative ranges. The interaction between resource environment and herbivory may elucidate mechanisms important for Guinea grass escaping cultivation in its introduced range and lays the foundation for future ecological studies and a search for biological control.
Citation
Rhodes, A. C.; Plowes, R. M.; Martins, D. J.; Ng'Iru, I.; and Gilbert, L. E., "Characterizing Invasiveness through a Descriptive Study of Guinea Grass (Megathyrsus maximus) Growing in Three Habitat Types and Differing Herbivore Assemblages in Both Kenya and Texas" (2022). IGC Proceedings (1993-2023). 6.
https://uknowledge.uky.edu/igc/24/1-2/6
Included in
Characterizing Invasiveness through a Descriptive Study of Guinea Grass (Megathyrsus maximus) Growing in Three Habitat Types and Differing Herbivore Assemblages in Both Kenya and Texas
Guinea grass (Megathyrsus maximus syn. Panicum maximum) is an important pasture grass that has been introduced pantropically, yet in many cases has escaped cultivation and is invading native rangelands – threatening biodiversity at multiple trophic levels. An increasing challenge of rangeland management is balancing the importance of pasture grasses with their negative impact on ecosystem processes. Given this challenge, it is critical to understand the mechanisms that underlie grass invasion. In this descriptive study, our objective was to assess the ecological stress release hypothesis by comparing the relative abundance and functional traits of Guinea grass in Kenya's home range with its introduced range in Texas, USA. To characterize Guinea grass dominance in Texas vs. Kenya, we measured plant height and cover and examined the associated arthropod and ungulate abundances. We characterized these associations across three habitat types of differing resource availability; 1) Under woody legumes with higher soil moisture and soil nitrogen, 2) grasslands with higher light yet drier soils, 3) riparian areas with higher soil water moisture and light. We found that Texas Guinea grass was 50% taller than Kenyan Guinea grass except for riparian environments comparable to its introduced range. Texan Guinea grass occupied 50% more area than Kenyan Guinea grass and was especially abundant under woody legumes. Texas ungulate communities were less diverse and abundant. The arthropod herbivore diversity was twice as high on Kenyan Guinea grass. These results suggest that Guinea grass has escaped a rich assemblage of herbivores and likely explains some of its spread in nonnative ranges. The interaction between resource environment and herbivory may elucidate mechanisms important for Guinea grass escaping cultivation in its introduced range and lays the foundation for future ecological studies and a search for biological control.
