Abstract: Activities of the four soil enzymes(i.e.invertase,urease,alkaline phosphatase and catalase),key to recycling of C,N and P,were studied under four different land use patterns in the Dongting Lake area.Results show that the effect of land use on soil enzyme activities in the surface layer(0-30 cm) was significant,and decreased gradually with depth of the soil profile.Among the four soil enzymes,urease,invertase and alkaline phosphatase were affected by land use throughout the entire soil profile,but the effects on catalase were only limited in the soil surface layer(0-30 cm).All the enzymes,except catalase that did not vary much,showed a downward tendency in activity with depth of the soil profile,which suggests that soil organic matter decomposition and soil nutrient recycling are closely related to the structure of soil profile.

Key words: Dongting Lake area, enzyme activity, land use, spatial distribution