The Water And Growth Function Of Main Afforestation Tree Species In Semi-arid Region On Loess Plateau

Forestry development can only depends on rain in semi-arid region on Losses Plateau. In the region, water is the key factor to limit the growth and survival rate of man-made forest. On the base of the SPAC theory, this paper studies how water influences the physiological activities and growth of the main trees for forestation. Then it chooses the transpiration water consumption as the factor to research the water and growth function of trees. The result can become the basic theory of artificial reforestation in the region.In May to September 2005, selected four trees (Ailanthus altissima, Prunus armeniaca, Larix gmelinii, Platycladus orientalis) to observe the factors of their physiological activities and growth, studied the relationship between the soil water content and the factors.The growth of the four trees was closely related to soil water, especially in July. In this period, low soil water content would badly affect the trees, and enough water must be offered. In May to September, all the factors except RS were become lower with the decrease of the soil water content. The lower, the worst.The relationship between the trees' growth and water is reflected by the relationship between growth and the transpiration water consumption. So takes the transpiration water consumption and the amount of trees' dry matter to make the water and growth function. The functions are: Y=0.4683Ln(x)-1 .4198(Ailanthus altissima) , Y=0.4355Ln(x)-1.2468 (Prunus armeniaca), Y=0.3672Ln(x)-1.0351(Larix gmelinii), Y=0.5795Ln(x)-1.8096 (Platycladus orientalis) .