A mechanism for the influence of vegetation on the response of the diurnaltemperature range to changing climate

We propose a new mechanism that could contribute to the observed decrease i n the diurnal temperature range (DTR) over the last century: the physiologi cal behavior of vegetation in response to climate. Using a physiologically based land surface model, we analyze the influence of vegetation on the res ponse of the DTR to perturbations in the state of the climate and vegetatio n. Increasing down-welling long wave radiation and surface air temperature together, conditions that could occur as a result of doubling of atmospheri c CO2, produced little change in the DTR. Changes in the state of the veget ation (i,e, amount, physiological capacity, stress) produce changes in the DTR of the order or larger than observed. Results emphasize that DTR modeli ng studies need to consider vegetation responses and suggest that recently reported increases in vegetation over the last decade could contribute to t he observed decreases in the DTR.