| The vegetation canopy stomatal conductance estimation is the basis of accurate simulation of evapotranspiration,on a global scale vegetation canopy stomatal conductance,the response of ecosystem vegetation to global change and adaptation mechanism,and to predict the future carbon water circulation under the background of global change between vegetation and atmosphere will be of important significance.In this study,statistical analysis of plant leaf stomatal characteristics,based on the Leuning-Ball model,and Franks model is constructed based on different types of vegetation canopy stomatal conductance model(Leuning-Franks model),and the introduction of Ball-Barry model and Leuning-Ball model of vegetation type is subdivided into C3,C4 vegetation(Leuning-Franks-BallBarry model,Leuning-Franks-LeuningBall model).The Leuning-Franks model was applied to simulate the stomatal conductance of maize canopy in Heihe basin.The canopy conductance was simulated by using the measured data of the experimental station and the Penman-Monteith formula,and the accuracy and sensitivity of the simulated canopy conductance were evaluated.In the Heihe basin,the changes in the stomatal conductance of the canopy of the Heihe River Basin from 6 to September 2012 and their spatial differences were simulated and analyzed by remote sensing data,and the following conclusions were drawn:(1)The stomatal density of vegetation leaves is different from that of vegetation length.The maximum stomatal density is 1439.9/mm2,the smallest is 15.4/mm2,and the length of leaf stomata is 5m?64.8m?64.8.The stomatal length of the leaves of the same genus is similar,but the stomatal density is different,and there is no uniform rule.(2)The simulation results of Leuning-Franks model are in good agreement with the measured values,the average correlation coefficient is 0.6454,and the consistency index is 0.7832.The sensitivity analysis showed that the Leuning-Franks model(L)in addition to the stomatal length and stomatal density(SD)is the most sensitive,leaf area index(LAI)and vapor pressure deficit(VPD)of the extinction coefficient(kQ)and maximum stomatal conductance of visible light flux density(Q50)of half the most insensitive.(3)The distribution of VPD in the Heihe basin is not very different,and the trend of decreasing from south to north is present.The 2.74kPa with the highest VPD value was in August;the peak value of LAI appeared in July,the highest value was 6.85,and the vegetation type was evergreen coniferous forest.The area with high leaf area index is mostly concentrated in the area of maize,grassland and forest.The photosynthetically active radiation varies with time and space.The spatial distribution is basically the same in every month.The total photosynthetically active radiation in September is the most significant.(4)The greater guide value is mostly in the southern meadow,the smaller the guide degree is generally in the south,and the thicket of the shrubs is more.The stomatal conductance of the vegetation canopy in the Heihe River Basin basically appeared below the middle reaches,showing increasing from north to south.The stomatal conductance of the vegetation canopy was greatly influenced by vegetation types in large scale,and the difference of vegetation canopy conductance in the same area was significant in different months.In 7 and August,the average stomatal conductance of the vegetation canopy in the Heihe river basin is relatively large,and the area in many places is above 0.01m/s,and the maximum value can reach 0.26m/s.In June,the average stomatal conductance distribution in Heihe basin was similar to that in September,and the total stomatal conductance was smaller than that in September,and the maximum value was 0.148m/s. |
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