Analysis For Causes Of Low-quality Sand-break Forest Of Populus ×xiaohei T.S. Hwang Et Liang In The West Of HeiLongjiang

This research aimed at influence of physical and chemical properties of soil,plant diseasesand insect pests on shelter belt's growen. Mainly mensurateed: the soil bulk specific gravity, thebulk porosity and the water content, the field capacity soil, can be studied by Link knife skilland drying law. Through the potential method, the potassium dichromate capacity-hotrelease. the alkaline hydrolysis diffusion,the soaking of 0.5mol/L sodium bicarbonatesolution,soil pH value,the organic matter, the hydrolysis nitrogen,the effective phosphorus theavailable potassinm,we can reseach the chemistry. The research was carried on three type placesin Hongqi forestry centre of Daqing,which had Populus×xiaohei T. S. Hwang et Liang. One ofthem grew well,while the others didn't.The result indicated that, The calcic horizon is thick and the distince from surface isshort.This is one of the reason for Low-quality forest The best fields of Populus×xiaohei T. S.Hwang et Liang, the deeps of calcic horizon appeared is deepest for 30.5cm in average. Thethickness of calcic horizon is thinnest for 23.3cm. The bad fields of Populus×xiaohei T. S.Hwang et Liang,the calcic horizon is most thick.At the layer of 5-10cm,The total porosity of the best fields of Populus×xiaohei T. S. Hwanget Liang is 39.3% and 38.6%. That is higher than the total porosity of the bad fields of Populus×xiaohei T. S. Hwang et Liang's 21.9%, 22.4% and 29.3%. At the layer of 20-25cm is so.The low content of available Phosphorus and available Potassium is one of the reason forLow-quality forest. The available Phosphorus of the best fields of Populus×xiaohei T. S.Hwang et Liang is 1.84mg/kg,1.68mg/kg. That is higher than the bad ones,which content is0.82mg/kg,0.83mg/kg and 1.07mg/kg. The content of available Potassium is so. The contentof available Potassium of the best one is 142.14mg/kg and 128.67mg/kg in average. It is distincthigher than the bad ones,which is 85.21mg/kg,85.93mg/kg and 109mg/kg.Density of holes of the best fields of Populus×xiaohei T. S. Hwang et Liang is 36,thedensity of holes in the bad ones,which is 129, 197 and 120. All of above,the insect pest has aheavy influence on the growing of the bad fields.