Effects of warming and altered precipitation regime on managed grassland structure and function 
Rebecca L. McCulley, University of Kentucky
Abstract
The proposed research will evaluate how managed grassland ecosystems respond to alterations in climate. The forage species that dominate these grassland systems have been selected for tolerance to climatic variability and herbivory, and they employ several strategies to accomplish these ecological feats (e.g., phenological plasticity, rapid maturation, production of secondary compounds, and associations with fungal endophtyes). The main objective of this proposal is to determine if managed grassland response to climate change can be predicted based on known species-specific physiological traits.
The over-arching hypotheses are that: 1) C4 and endophyte-infected C3 forage species will maintain higher rates of productivity under warmer, drier environmental conditions than endophyte-free C3 species; however, increases in secondary chemical production resulting from the increased dominance and activity of these species will alter the microbial community and slow nutrient cycling rates; and 2) These species-level responses will result in alterations in carbon and nitrogen storage within the plant-soil system.
This research project will occur primarily in a managed grassland located at the University of Kentucky’s Spindletop Agricultural Farm located near Lexington, KY.
I will utilize a field climate manipulation approach, where both precipitation and temperature modified in a mixed species managed grassland. Four climate treatments will be implemented: increased average annual daily air temperature (3-4°C), increased summer precipitation (+10% mean annual precipitation), increased temperature and precipitation, and an ambient control. I will measure both ecosystem (e.g., above- and belowground net primary production, litter quality and decomposition rates, nitrogen mineralization rates, trace gas fluxes, and nutrient pools) and species-specific parameters (e.g., leaf water potentials, photosynthesis rates, secondary compound concentrations, and endophyte infection frequencies) in order to determine if ecosystem response to climate change is controlled by species traits.
This project will quantify the response of common, broadly utilized forage species and the managed grassland ecosystems they form to alterations in precipitation and temperature (Focus 1). The resulting data and database will inform modeling efforts that attempt to predict the response of this ecosystem type to future alterations in climate.
