Abstract:

The heat pulse technique was applied to study the variation of the stem sap flow of individual plant of Populus euphratica in different direction and depth of trunk in the Ejina oasis in the lower reaches of Heihe River. The results showed that the sap flow velocity increased with increment of depth and arrived at the maximum in 15 mm, and subsequently decreased gradually. The closer the point was to cambium, the earlier the sap flow moved. In four direction, the sap flow velocity in the south and west was more than that in the north and east; The sap flow in the south moved earlier and dropped more quickly than that in the west; The sap flow velocity was similar in the north and east. Based on it, the water transportation of near-mature P. euphratica stand was calculated using stem area as a scalar. There was a high correlation between the stem area of P.euphratica forest and diameter by power function. So the stem area of forest could be calculated by the distribution of diameter measured in the field. The water consumption of near-mature P. euphratica forest in the lower reaches of Heihe River in the growth season from May to October was 3 172 m³·hm^-2 by measuring the sap flow flux of individual plant with heat pulse technique.

Key words: Populus euphratica, sap flow of individual plant, forest water consumption