In order to understand the effects of different improving patterns for badly degraded Robinia pseuc-doacacia plantation in the Yellow River Delta area

soil enzyme activity

soil density

porosity

saline-alkali content and soil nutrients under the plantation improved for five years were determined. Four improving measures

including cotton field

pure forest of Fraxinuschinensis

agro-forestry of F. chinensis + cotton and mixed forest of F. chinensis + R. pseucdoacacia

were selected

with the badly degraded R. pseuc-doacaciaplantation serving as the control (CK). Results are as follows:(1) The improving patterns clearly affected soil phosphatase

urease and polyphenol oxidase

but not soil peroxidase. Soil phosphatase and ure-ase activity increased

but soil polyphenol oxidase decreased. The activities of polyphenol oxidase and urease showed such an order of mixed forest>pure forest>agro-forestry>cotton field. Phosphatase activities in mixed forest

agro-forestry

pure forest and cotton field were 3.5

3.2

1.7and 1.6times of that of CK

re-spectively. (2) Soil density and soil salt content decreased after adopting the four improving patterns

a nd these indexes were in the order of mixed forest