Sensitivity Experimental Study On The Response Of Future Arid Region Evolution To Changes In Vegetation Stomatal Conductance

Under the background of global climate change,accurate estimation of potential evapotranspiration(PET)change and evolution of drylands is very important to predict future drought situation and climate change.In this study,Penman-Monteith equation was used to conduct numerical experiments,and the global PET change characteristics and the evolution law of drylands in the future with the change of vegetation stomatal conductance were analyzed in detail.The results show that the traditional Penman-Monteith may overestimate the growth of pet and the expansion of arid areas in the future.The main conclusions are as follows:(1)In addition to SSP126,PET in the world and all continents will show a growth trend in the future.The most obvious areas growth is in Oceania and Africa.The higher the CO₂concentration,the more obvious the growth trend of PET in the later stage of the future.With the decrease of stomatal conductance,the trend of PET in the world and all continents decreases(except for the later stage of SSP126).The most obvious areas decline is in Oceania and Africa,and the more obvious the decline is in the situation of higher CO₂concentration.(2)In the SSP126 scenario,the mainland will be mainly controlled by temperature in the early stage and relative humidity in the later stage;Under the SSP245 scenario,in the later stage of the future,northern North America and other regions will change from temperature control to relative humidity control,and Central Africa will change to net radiation control;In the context of SSP370,the dominant factors in a small part of the region change from temperature to CO₂;In the later stage of SSP585 scenario,except that the dominant factor in northern North America and Northern South America is temperature,the dominant factor in most regions(83.85%)changes to CO₂.(3)The expansion of arid areas in the future is mainly the growth of humid and dry areas and semi-arid areas.With the decrease of stomatal conductance,the area of global dryland will be reduced by 0.69%?0.93%?1.27%and 1.10%respectively.Later in the future,with the decrease of stomatal conductance,in the climate scenario with higher CO₂concentration,the shrinking area of arid area will be more,shrinking by 0.98%?1.79%?3.01%and 4.86%respectively.The area is mainly in central North America and eastern South America,indicating that previous studies overestimate the expansion of arid area,and the overestimation is more obvious in the climate scenario with higher CO₂concentration.(4)Under the climate scenarios of SSP126 and SSP245 with low CO₂concentration,the area dominated by PET is decreasing,while under the scenarios of SSP370 and SSP585with high CO₂concentration,the area dominated by PET is increasing.Except for SSP126,with the decrease of stomatal conductance,the area with PET as the dominant factor continues to decrease,and the decrease is more obvious in the climate situation with higher CO₂concentration,which is mainly reflected in the transformation of the dominant factor from P to PET in eastern North America and from PET to P in some parts of Central Asia.