Study on the Transpiration Characteristics of 10 Species of Plants under the Different Depths of Groundwater Level

By applying the lysimeters, in this paper the transpiration characteristics of 10 species of psammophytes and xerophytes including Haloxylon ammoderdron, Caragana korshinskii, etc. in Minqin County, Gansu Province, are investigated. The results show that, from the high value to the low value, the total transpiration of the tree species in 5 years is in an order: Elaeagnus angustifolia: 4 303.32 kg; Hedysarum scoparium: 3 287.02 kg; Atraphaxis bracteata: 1 406.29 kg; Caragana korshinskii: 1 312.34 kg; Haloxylon ammodendron: 1 138.27 kg; and Calligonum leucocladum: 726.86kg. The transpiration coefficients of the tree species are in a decrease tend but the evapotranspiration coefficients are in an increase tend with the increase of their age. The transpiration occurs mainly during the period from June to September, which occupies 80%～90% of the total annual transpiration. The transpiration of the plants was going up with the increase of age and the increment of transpiration rate varied with different species. The transpiration of the plants increases rapidly with the increase the plants' age, however, the increase amplitudes are different from the different species of plants. Both Calligonum leucocladum and Calligonum mongulicum can reach the maximum height in 2～3 years after planting, therefore, they have the quickest growth and the highest increment of transpiration.