Responses to climate change of C4 and C3 species native to South-central Region

P.I.Institution: K. Raja Reddy, Mississippi State University

Co-PI/Institution: V.G. Kakani, Mississippi State University

What hypotheses are to be tested or what question (goal) will be answered by the proposed research?
Climate change models project an increase in atmospheric CO2 concentration, air temperature, surface ozone and UV-B radiation, and variation in precipitation patterns in the current century. Global climate change would alter the vegetation patterns on Earth’s surface. The impact studies of projected climate change were mainly restricted to crop species. Studies conducted so far to determine changes in vegetation pattern of natural ecosystems, either through experimentation or modeling, were based on the vegetative growth or biomass determined by photosynthesis of the species. Several other plant physiological processes respond to changing climates that determine plant adaptation. Under natural environments, distribution and succession of a species is through reproduction, and products of reproduction (seeds) play an important role in population establishment. Research was not carried so far to study the effects of climate change on reproduction of native species in US Southcentral region in general and Mississippi in particular that include both C3 and C4 types. Although increase in CO2 is known to increase biomass, we hypothesize that increase in intensity, frequency and duration of temperature would reduce the reproductive ability of the species native to Mississippi.

What is the importance of the question or hypothesis? Anthropogenic factors cause increases in atmospheric CO2, leading to higher global mean temperatures and changes in amount and timing of precipitation. The CO2 and temperature are essential factors for vegetation distribution dynamics on a given geographic region. Our proposed experiments will provide a unique data set describing interaction effects between rising CO2 and temperature on the growth and reproduction of species native to Mississippi in the South-central region. The response functions and interactions effects on reproduction can be incorporated into current ecological models to simulate the changes in vegetation density and distribution.

Summary of proposed work: This project addresses the long-term goal of understanding the interactive effects of increasing atmospheric carbon dioxide concentration ([CO2]), surface air temperature, water deficit and UV-B on native C3 and C4 species of Mississippi in the South-central region. Despite many experiments on the effects of elevated CO2 alone on many species, there are still few studies that have addressed the interactive effects of elevated CO2, and temperature stress, none with native species of Mississippi. Here we propose to fill these knowledge gaps using a unique outdoor controlled environment facility that will allow us to examine these interactions in select species (Big Bluestem (Andropogon gerardii) and Virginia wildrye (Elymus virginicus) of the Mississippi of the Southentral region. The immediate objectives of this proposal are to test the hypothesis that elevated [CO2] in interaction with temperature will modify the response of seed set in native grass species and to understand the physiological, biochemical basis of these interactions. The species will be grown from sowing to maturity in elevated and current and elevated atmospheric [CO2] in combination with a range of temperatures for the current growing region of the species. The outcome of the project will identify and assess the performance of these species in response to these climatic variables and to develop response functions that can be used to detect change in composition of these species in the natural environment. These algorithms, once integrated into ecological models, can be used to detect climate change-induced species distribution patterns across a wider area, and also serve as model species for other grasses native to this area.