北方典型半干旱区不同林龄樟子松人工林蒸腾速率和气孔导度变化特征OA

To explore the transpiration water consumption processes and the age-dependent differences in stomatal regulation of Pinus sylvestris var.mongolica plantations in semi-arid sandy areas,we selected 13-,32-and 41-year-old P.sylvestris var.mongolica plantations in Zhanggutai area at the southern edge of Horqin Sandy Land as research objects.Sap flow density was continuously monitored,and meteorological factors and soil volumetric water content were simultaneously meas-ured.On this basis,canopy stomatal conductance and dimensionless decoupling coefficient were inversely calculated.The results showed that the transpiration of P.sylvestris var.mongolica plantations at three stand ages was all affected by envi-ronmental conditions,while their adaptive ranges varied among different stand ages.Air temperature,vapor pressure defi-cit and photosynthetically active radiation were the key factors controlling transpiration per unit leaf area.The mean tran-spiration per unit leaf area during the growing season for young,middle-aged and mature stands was 0.44,0.75 and 1.35 mm·d-1,with cumulative values of 71.79,121.16 and 216.83 mm,respectively.Stomatal conductance exhibited slight fluctuations throughout the growing season,with average values of 67.82,83.55 and 109.04 mmol·m-2·s-1 in se-quence.The average dimensionless decoupling coefficient was 0.190,0.140 and 0.044,indicating that the canopy of P.sylvestris var.mongolica in the study area was strongly coupled with the ambient atmosphere,and transpiration variation was largely restricted by stomatal behavior.Stomatal conductance was negatively correlated with vapor pressure deficit.The fitted slopes of young,middle-aged and mature stands were-24.325,-32.893 and-10.362,respectively.This sugges-ted that stomata of young and middle-aged stands were more sensitive to atmospheric drought.Although mature stands maintained relatively high stomatal conductance,their response amplitude to changes in vapor pressure deficit was smaller.Overall,stand age altered the transpiration intensity,stomatal sensitivity and canopy-atmosphere coupling degree of P.syl-vestris var.mongolica plantations,thereby affecting their water regulation strategies under semi-arid environments.