Seasonal Dynamics of Dominant Grasses in the Nutrient Network
C3 and C4 grasses have varying physiological adaptations in grassland ecosystems, including C3 grasses being able to dominate when nutrients and water are plentiful, and C4 grasses dominating in hotter and drier conditions. Species competition for limiting resources depends on ecophysiological tradeoffs. Nutrient addition may shift these competitive balances, leading to tradeoffs in spatial and temporal partitioning. C3 and C4 grass interactions in grassland ecosystems may rely on nutrient availability to influence the ecophysiological tradeoffs, which cause shifts in abundance and competitive ability throughout the growing season. Looking at the seasonal dynamics of dominant C3 and C4 grasses' physiology and relating to competitive outcomes and ecosystem functions helps to describe the competitive shifts caused by excess nutrient availability, determining which grasses may be more abundant in eutrophied ecosystems. This was studied by measuring (1) competitive outcomes through percent cover, (2) nutrient use efficiency through leaf C:N ratio, and (3) light competition through light asymmetry and height, between Elymus repens–the dominant C3 grass at the study site–and Andropogon gerardii–the dominant C4 grass at the study site–throughout the 2022 growing season. The data was analyzed to determine the main cause of changes in dominance between the C3 and C4 grasses in plots with NPK addition, compared to Control plots.