Ecophysiology and ecosystem-level impacts of an invasive C4 perennial grass, Bothriochloa ischaemum

dc.contributor.advisorFowler, Norma L.
dc.contributor.advisorLitvak, Marcy E.
dc.creatorBasham, Tamara Sueen
dc.date.accessioned2014-02-11T17:47:31Zen
dc.date.issued2013-12en
dc.date.submittedDecember 2013en
dc.date.updated2014-02-11T17:47:32Zen
dc.descriptiontexten
dc.description.abstractThe anthropogenic introduction of species into new ecosystems is a global phenomenon, and identifying the mechanisms by which some introduced species become dominant in their introduced ranges (i.e., invasive) is crucial to predicting, preventing, and mitigating the impacts of biological invasions. Introduced perennial C₄ grasses are invading semi-arid grassland and savanna ecosystems throughout the south-central U.S. We hypothesized that in these semi-arid ecosystems, where variable precipitation patterns strongly influence vegetation dynamics, the success of an invasive plant species may be due in part to ecophysiological traits that enable high performance in response to unpredictable water availability. We also hypothesized that increased primary productivity and decreased plant input quality associated with these grass invasions have the potential to alter ecosystem carbon and nitrogen cycling and storage by altering the ratio of inputs (productivity) to outputs (decomposition/respiration). We tested the first hypothesis by quantifying ecophysiological performance differences between an invasive C₄ grass, Bothriochloa ischaemum, and co-occurring C₃ and C₄ native grasses under wet and dry conditions in the field and under two levels of simulated precipitation frequencies in a greenhouse experiment. We tested the second hypothesis by examining whether increased primary productivity and decreased C₃:C₄ grass ratios in savanna grass-matrices associated with B. ischaemum invasion altered (1) plant input quality and thus nutrient cycling and/or (2) net ecosystem carbon uptake in invaded areas. B. ischaemum's success as an invader was not directly related to its ability to cope with precipitation variability and availability, but its ability to rapidly produce large amounts of biomass may allow it to directly out-compete native species. B. ischaemum invasion decreased plant input quality and soil nitrogen availability. B. ischaemum invasion shifted ecosystem C-uptake from being nearly year-round to occurring predominantly in the summer. Greater C-uptake during the summer and under drier conditions compensated for a shorter growing seasons in B. ischaemum-invaded areas and cumulative annual NEE was similar between invaded and native-dominated areas. We conclude that B. ischaemum's impacts on soil nitrogen availability and plant-canopy microhabitat may allow it to exclude native species from invaded areas, but that its impacts on ecosystem C sequestration may be small.en
dc.description.departmentPlant Biologyen
dc.format.mimetypeapplication/pdfen
dc.identifier.urihttp://hdl.handle.net/2152/23141en
dc.language.isoen_USen
dc.subjectInvasive speciesen
dc.subjectEcophysiologyen
dc.subjectNet ecosystem carbon exchangeen
dc.subjectSoil nitrogenen
dc.subjectNutrient cyclingen
dc.subjectStanding dead residence timeen
dc.subjectLitter qualityen
dc.subjectLitter decompositonen
dc.subjectSoil respirationen
dc.subjectPerennial grassen
dc.titleEcophysiology and ecosystem-level impacts of an invasive C4 perennial grass, Bothriochloa ischaemumen
thesis.degree.departmentPlant Biologyen
thesis.degree.disciplinePlant Biologyen
thesis.degree.grantorThe University of Texas at Austinen
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophyen
Files
Original bundle
Now showing 1 - 1 of 1
Loading...
Thumbnail Image
Name:
BASHAM-DISSERTATION-2013.pdf
Size:
2.08 MB
Format:
Adobe Portable Document Format
License bundle
Now showing 1 - 2 of 2
No Thumbnail Available
Name:
LICENSE_1.txt
Size:
1.84 KB
Format:
Plain Text
Description:
No Thumbnail Available
Name:
LICENSE.txt
Size:
1.84 KB
Format:
Plain Text
Description: