Hard To Cover The Impact Of Street Trees On City Streets Soil Respiration

The respiration of the crust－covered soil under the trees along the People's Street in Changchun city was measured using captive test in this paper. The chemical and physics qualities, temperature, the changing of microbes' content of the crust covered soil and the influence to the respiration of the soil were studied. The result showed as following:The arrangement and the structure of the soil were changed by the crust－covered paving. It made the capacity of soil bigger, the hole smaller and the organic materials less,however it had little influence on the content of the N,P,K in the soil. The content of the microbes in the soil was decreased and the process of the translation between the biology and chemistry of nutriments was hindered by the crust－covered paving. It is very harmful for the providing of the nutriments to the trees growing.The crust－covered paving would lead to the higher temperature of the soil under the same conditions and burn the root in the surface layer and stock when under the summer high temperature. Plant cells could not adapt to the great temperature change for the freezing between the cells and in the cells which would lead to the break of cell membrane and in the end lead to the death of the trees when the autumn is coming.The air exchange between the air and the soil would be hindered by the crust－covered paving. It increased the concentration of CO2 in the soil. With the stress of high concentration of CO2 for a long time, the roots had to respire under anaerobic condition. Ultimate products (lactic acid, mainly ethanol)would prevent the growth of the roots and the transit of the consume iron. The infiltration of the roots would decrease and finally,the trees would die. The improvement methods to the soil conditions under the crust－covered paving were put forward as following:The area of the crust－covered soil should be decreased and the area of the uncovered soil should be increased so that there is enough soil capacity for the trees' growing. If condition permitted, the paving which can make the breath freely or soft covered paving should be used instead of the crust－covered soil. The pipeline or the well to make soil breathe freely should be put under the ground if necessary. The methods of improving the soil conditions and supplying water and nutriment to soil should be adapted in order to improve conditions for the trees growing.