Variation of Stem Sap Flow in Prunus Sibirica L.in North Shaanxi Province

The dynamics of sap flow rates in apricot and related environmental factors in ecotone of agriculture and animal husbandry were observed using TDP sap flow measuring meter from May to September in 2009 in Wuqi County.The results showed that:(1) Abroad peak curve of diurnal sap flow change was occurred in apricot forest with the beginning of sap flow at 7:40 and the peak value at 12:00—14:00 and the quick declining at 18:30.And obvious stopping sign of the sap flow did not exist even at night.Moreover the sap flux from 8:00 to 18:30,which accounted for 60% of the sap flux of whole day,was the major part of sap flux.(2) The significant difference in the change of sap flow was detected in typical sunny and rainy day with a higher daily sap flow rate in sunny day than in rainy day.(3) The value of sap flow increased first and then decreased with time.And the highest value occurred in July with a mean value of 64.247 g/h,followed in June whose mean value was 58.139 g/h,while the lowest value of 49.156 g/h appeared in September.(4) The variation trend of sap flow in bough was similar to that in lateral branch.But compared to lateral branch,the bough had a higher sap flow velocity.The lateral branch was more sensitive to the variation of environmental factors than the bough and the response of bough to sap flow was slower than lateral branch and showed an obvious lag efffect.(5) There was significant difference in the sap flow rate of apricot among different positions.The sap flow rate in the upper side is higher than that in the middle part which is higher than lower part.(6) Environmental factors influenced the sap flow variances of apricot.The order of intensity of influence was as follows: air temperaturesaturation vapor pressurerelative humiditysolar radiationwind speedsoil temperature.