[Artifical improvement of soil fertility in a regraded forest ecosystem by using municipal sewage sludge].

The increasing occurrence of forest ecosystem degradation is a serious problem in tropical and subtropical regions. Field experiments showed that the application of sludge from a sewage treatment plant could not only promote the growth and reproduction of trees, including the increase in the height and diameter of trees and thus being advantageous to the growth of shrub and herb of trees, but also improve soil fertility such as increasing soil organic matter and available nitrogen and phosphorus. The test of residual heavy metals of soil indicated that the application of sludge increased the content of Pb in the soil and the increment of Pb was varied with the increase of sludge usage. There was no significant increase in other heavy metals.