Responses of an old-field plant community to interacting factors of elevated [CO2], warming, and soil moisture

Aims: The direct effects of atmospheric and climatic change factors—atmosphericCO₂], air temperature and changes in precipitation—canshape plant community composition and alter ecosystem function.It is essential to understand how these factors interact tomake better predictions about how ecosystems may respond tochange. We investigated the direct and interactive effects ofCO₂], warming and altered soil moisture in open-top chambers(OTCs) enclosing a constructed old-field community to test howthese factors shape plant communities. Materials and methods: The experimental facility in Oak Ridge, TN, USA, made use of4-m diameter OTCs and rain shelters to manipulate CO₂] (ambient,ambient + 300 ppm), air temperature (ambient, ambient + 3.5°C)and soil moisture (wet, dry). The plant communities within thechambers comprised seven common old-field species, includinggrasses, forbs and legumes. We tracked foliar cover for eachspecies and calculated community richness, evenness and diversityfrom 2003 to 2005. Important findings: This work resulted in three main findings: (1) warming had species-specificeffects on foliar cover that varied through time and were alteredby soil moisture treatments; (2) CO₂] had little effect onindividual species or the community; (3) diversity, evennessand richness were influenced most by soil moisture, primarilyreflecting the response of one dominant species. We concludethat individualistic species responses to atmospheric and climaticchange can alter community composition and that plant populationsand communities should be considered as part of analyses ofterrestrial ecosystem response to climate change. However, predictionof plant community responses may be difficult given interactionsbetween factors and changes in response through time.