绿洲农田防护林树干水分传输的方位差异OA北大核心CSTPCD

[Objective]This study aims to determine the azimuthal variations of water transport in the sapwoods of the trees under special site conditions,so as to provide a scientific basis for improving the accuracy in estimating tree transpiration by sap flow through observing and comparing the sap flow velocity of sapwoods facing and backing to an irrigation channel in the oasis farmland protection forest trees planted alongside the channel.[Method]Three typical poplar species(Populus×popularis,P.alba var.pyramidalis and P.deltoides cl.Beikang)in the oasis farmland shelterbelt in Ulan Buh Desert were selected as the research objects.The heat field deformation(HFD)method was used to synchronously monitor the sap flow velocity of the trunk that was either face to or back to the irrigation channel in eight measuring sites.[Result]Sap flow velocity of sapwood facing to the irrigation channel(JQ-side)was significantly higher than that of sapwood backing to the irrigation channel(JNQ-side)in each tree species(P<0.01).JQ-side values of P.×popularis,P.alba var.pyramidalis and P.deltoides cl.Beikang were 1.83(R2=0.90),1.40(R2=0.71)and 3.55(R2=0.71)times of corresponding JNQ-side values,respectively.On sunny days,the average JQ-side peak values of the three tree species were 3.38,2.47,and 5.35 cm·h-1,respectively.The differences in sapwood sap flow velocity between the two sides reached the maximum around noon.Both JQ-side and JNQ-side showed a decreasing trend with the increase of sapwood depth,and the sap flow velocity at each point(1.5-7.5 cm)of sapwood facing to the irrigation channel was significantly higher than that of sapwood backing to the irrigation channel(P<0.01).The radial variation pattern of sap flow velocity in different azimuths in each poplar specie was consistent,which could be well fitted by the negative exponential function(R2>0.98).[Conclusion]The irrigation channel causes significant differences in the sapwood water transport between facing side and backing side to the channel,but does not change the radial variation pattern of sap flow of the trees in farmland shelterbelt.