Abstract:

Water is the key factor to vegetation growing in Loess area. Therefore, researchers are keen on the study of tree transpiration for a long time. In order to provide the scientific basis and practical instruction for the vegetation reconstruction and recovery in Loess area, the paper measured and calculated water consumption of potted Platycladus orientalis, Robinia pseudoacacia, Armeniaca vulgaris and Pyrus hopeiensis separately during the growing season (from Apr. to Nov.), which were the main afforestation species in western Shanxi of Loess area, based on the principle of water balance. Besides, according to the data of soil water dynamic and the range of available moisture of potted mature trees, the relationship between water supply and consumption and the soil moisture availability and deficit state were analyzed. Several conclusions are listed as follows: 1) In the dry year (2002), during the growing season the precipitation was 430.7 mm and the water consumption of potted trees was from 430 mm to 490 mm. More water consumption and less available water supply occurred, showing a serious water deficiency. In the rainfall_rich year (2003), during the growing season the precipitation was 870.2 mm and the water consumption of potted trees was from 480 mm to 515 mm. Due to uneven distribution of rainfall, the water budget lost balance a bit in May and Nov. 2) The curves of soil water content of different species had similar change trends in annual but different in the same month, and those of the same tree species in different test plots had different change trends in the same month either. 3) Non-available soil water content of P. orientalis, R. pseudoacacia, A. vulgaris and P. hopeiensis was less than 8.0%, 8.4%, 9.2% and 9.7% respectively, which indicated that P. orientalis used water more efficiently than others. In the deficit water year (2002), for several months, soil water content of potted trees was lower than its non_available soil water content, which could influence trees healthy growing. After supplements of precipitation of winter in the year and spring in the next year, soil water contents were higher than the lower limit of soil readily available moisture content, which implied that interannual water supply and consumption could keep balance.

Key words: afforestation species, water consumption of single tree, soil water characteristic curve, Loess area