Study On The Influence Of Two Kinds Of Poplars Shelterbelts On The Salt Balance In The Hetao Area

The issue about'Influence of Farmland Shelterbelt to Salt Equilibrium in Irrigation Area'is rarely reported. This paper studies the influence of P. Popularis'〔Populus simonii×(Populus pyramidalis+Salix matsudana)cv.'Poplaris'〕shelterbelt and P. alba var.pyramidalis(P. alba var.pyramidalis) shelterbelt to the salt equilibrium in the protecting zone in Hetao irrigation area and supplies basic data to the analysis on the equilibrium of water and salt and irrigation area management.The soil and ground water in irrigation area is an open system. The study focuses on the soil. When the soil salt content changes, it is difficult to distinguish that is resulted from shelterbelt or other factors. The paper studies the water use at different stage, the salt ion concentration in each part at different stage and the biomass in different part of the standard wood, inquires into their saltness and analyses the movement of salt ion in the tree~water use~soil (groundwater) system. By adopting heat equilibrium method, the paper studies the function of the two kinds of shelterbelts to decrease evaporation and saltness of surface soil in the farmland. The main conclusions are: 1) Both shelterbelts have the effective function to reduce evaporation and the salinity accumulation of the soil in cultivation layer in the protecting zone, the water saving and salt reducing function of the shelterbelt of P. Popularis'is superior to that of the shelterbelt of P. alba.var.pyramidalis at the same age. 2) The 90% of salt ion, which is in the water use of the two kinds of poplars, is accumulated in the soil—ground water system under the woods and has the tendency to reduce the composition ratio of Ca2+ there, the function to increase salt content under woods of P. Popularis'is bigger than that of P. alba.var.pyramidalis. 3) Some salt can be taken away when both of the two poplars are cut but their salt reducing function can be neglected. 4) The water use of P. alba var.pyramidalis is less than that of P. Popularis'.The paper also makes some basic research and the results are: 1) Both poplars have the similarity in the absorbability of soluble salt ion and its distribution in different part of...