Effects of climate change on water use efficiency in rain-fed plants

Document Type: Research Paper

Authors

Institute of Atmospheric Environment, China Meteorological Administration (Shenyang).

Abstract

Water use efficiency (WUE) reflects the coupling of the carbon and water cycles
and is an effective integral trait for assessing the responses of vegetated ecosystems
to climate change. In this study, field experiments were performed to examine leaf
WUE (WUEleaf) in response to changes in CO2 concentration and other
environmental variables, including soil moisture and air temperature. We also used
yield of maize and soybean, soil water content and precipitation data to calculate
water use efficiency at the level of grain yield (WUEgrain) in a manner that enabled us
to analyze the effects of climatic factors on WUEgrain. The results showed that the
WUEleaf measurements of maize and soybean plants were negatively correlated with
soil moisture and air temperature. At a photosynthetically active radiation (PAR) of
1.600 μmol m-2s-1, increasing ambient CO2 concentrations (from 400 to 800 μmol
mol-1) improved WUEleaf by 52.0% and 75.8% for maize (a C4 species) and soybean
(a C3 species), respectively. Increased annual precipitation stimulated maize WUEgrain
up to levels of approximately 500-550 mm, although maize WUEgrain decreased when
annual precipitation exceeded 550 mm. It appears that 400-450 mm is an economical
evaportranspiration (ET) for spring maize in Chaoyang area of northeast China. For
soybean, more water often reduces WUEgrain, and there is a linear relationship
between changes in WUEgrain and changes in annual temperature. The different
responses of WUEgrain and WUEleaf to climate change suggest that caution should be
taken when attempting to up-scale WUE from leaf to grain or biomass levels.

Keywords