Comparative Analysis of Drought Tolerance in Native and Invasive Grass Species

Thesis Abstract

Drought stress poses a significant threat to grassland ecosystems worldwide, adversely affecting plant vitality, biodiversity, and forage productivity. Within this context, the differential drought tolerance between native and invasive grass species warrants comprehensive investigation to inform sustainable management practices and ecological restoration efforts. This study aims to compare the physiological, morphological, and biochemical responses of selected native and invasive grass species to drought conditions, thereby elucidating their adaptive mechanisms and resilience thresholds. The specific objectives are to (1) assess variations in plant water use efficiency, stomatal behavior, and root system architecture under water deficit; (2) examine changes in biochemical markers such as proline, malondialdehyde (MDA), and antioxidative enzymes; and (3) identify phenotypic traits associated with drought tolerance through multivariate analysis. The research adopts a comparative cross-sectional design, integrating both controlled greenhouse experiments and field surveys across semi-arid regions. The population comprises four native grass species—Panicum maximum, Andropogon gerardii, Bouteloua dactyloides, and Panicum virgatum—and four invasive counterparts—Cenchrus ciliaris, Melinis repens, Saccharum officinarum, and Cynodon dactylon. A stratified random sampling technique was employed to select 30 healthy mature plants per species, totaling 240 specimens. Data collection encompassed physiological measurements (e.g., stomatal conductance via porometers, chlorophyll fluorescence), morphological assessments (e.g., root length density, biomass), and biochemical assays (e.g., proline via spectrophotometry, MDA levels through thiobarbituric acid reactive substances assay). Soil moisture content and climatic parameters were recorded to contextualize drought severity. Data analysis incorporated Analysis of Variance (ANOVA) to examine interspecies differences, multivariate regression models to identify predictors of drought resilience, and principal component analysis (PCA) to reduce data dimensionality and reveal trait syndromes associated with tolerance. It is anticipated that invasive species will exhibit enhanced drought resilience, characterized by higher water use efficiency, robust root systems, and elevated levels of osmoprotectants such as proline, alongside more effective antioxidative responses. These findings are expected to highlight key adaptive traits that confer resilience, with implications for both management of invasive populations and conservation of native biodiversity under increasing drought frequency and intensity driven by climate change. The study contributes to the existing body of knowledge by elucidating trait-based mechanisms underpinning drought tolerance among grass species, integrating physiological, biochemical, and morphological perspectives in a comparative framework, and applying the theoretical model of stress adaptation as posited by the Stress-Response Theory. In conclusion, results will inform ecological restoration initiatives aiming to select drought-resilient native species and devise management strategies to curb invasive spread. Recommendations include fostering native species with traits identified as markers of drought tolerance and developing integrated management frameworks that leverage ecological resilience. The study also advances methodological approaches in plant stress physiology research, providing a template for future cross-species comparative analyses. Further studies are suggested to explore genetic gene expression profiles associated with drought adaptation and to validate laboratory findings under long-term field conditions.