资源环境科技发展态势分析平台

From 1890 to 2015, anthropogenic carbon dioxide emissions have increased atmospheric CO2 concentrations from 270 to 400mol mol(-1). The effect of increased carbon emissions on plant growth and reproduction has been the subject of study of free-air CO2 enrichment (FACE) experiments. These experiments have found (i) an increase in internal CO2 partial pressure (c(i)) alongside acclimation of photosynthetic capacity, (ii) variable decreases in stomatal conductance, and (iii) that increases in yield do not increase commensurate with CO2 concentrations. Our data set, which includes a 115-year-long selection of grasses collected in New Mexico since 1892, is consistent with an increased c(i) as a response to historical CO2 increase in the atmosphere, with invasive species showing the largest increase. Comparison with Palmer Drought Sensitivity Index (PDSI) for New Mexico indicates a moderate correlation with C-13 (r(2)=0.32, P<0.01) before 1950, with no correlation (r(2)=0.00, P=0.91) after 1950. These results indicate that increased c(i) may have conferred some drought resistance to these grasses through increased availability of CO2 in the event of reduced stomatal conductance in response to short-term water shortage. Comparison with C-3 trees from arid environments (Pinus longaeva and Pinus edulis in the US Southwest) as well as from wetter environments (Bromus and Poa grasses in New Mexico) suggests differing responses based on environment; arid environments in New Mexico see increased intrinsic water use efficiency (WUE) in response to historic elevated CO2 while wetter environments see increased c(i). This study suggests that (i) the observed increases in c(i) in FACE experiments are consistent with historical CO2 increases and (ii) the CO2 increase influences plant sensitivity to water shortage, through either increased WUE or c(i) in arid and wet environments, respectively.