Do Internal N Signals Regulate Interspecific Variability in N Uptake Response to Elevated CO?

University Of Illinois At Chicago, Chicago IL

Investigators

Abstract

While there is a general consensus among scientists that the projected rise in the concentration of atmospheric CO2 will have a profound impact on productivity and composition of terrestrial ecosystems, our capacity to reliably predict the exact nature of these changes remain tenuous. The unknown effects of other environmental factors such as nitrogen (N) and water are major sources of this uncertainty. N is an essential mineral nutrient whose availability and utilization regulates plant responses to high CO2. This high leverage by N is fortuitous when one considers the intricate connection between carbon (C) and N in plant biology. It is well recognized that in the short term, plants exposed to high CO2 will enhance their C uptake. Theoretically, however, only those species that can maintain a balance between N and C demand will sustain a long-term positive effect. The few available data indicate that plant species vary widely in their N uptake responses to high CO2. However, observations from a few empirical studies can not be extrapolated to cover a wide range of species around the globe and we currently lack a mechanistic understanding to develop such a roadmap. Here we propose to elucidate the major mechanism(s) that control plant N uptake when CO2 concentration is elevated using species from contrasting ecosystems. We propose to develop physiological and biochemical markers that could be used to gauge the extent to which a target species can maintain its N and C balance. The physiological and biochemical markers targeted here are known to control plant N uptake under natural conditions and therefore are likely to control N uptake responses under high CO2 as well. The findings are equally important for basic research and management/policy issues that must deal with increasing pressure to cope with the future climate. The proposed research will be conducted at six nationally funded Free Air Carbon dioxide Enrichment (FACE) experiments, two CO2 natural springs in Italy and New Zealand, and a number of open-top chambers at the University of Illinois at Chicago. The results generated here will be critical for the development of predictive models designed to forecast the fate of terrestrial ecosystems in a future climate.