Abstract:

 Soils were sampled in rape field， native wetlands， and wetlands returning from farmland to lake within different periods （3， 7， 9， 11 and 21 years） to analyze changes of soil physicochemical properties and microbial biomass carbon and nitrogen The results showed that soil bulk density decreased with the increase of periods since farming abandoned For example， the soil bulk density in abandoned farmland within 3 years was 151 g/cm3 while that in abandoned farmland within 21 years was 079 g/cm3. Soil moisture and clay content increased gradually with abandoning period， moreover the water content of abandoned farmland in 21 years was 2100% higher than that of rape field， and 687% higher than that of 3 years abandoned farmland. The clay content of 21 years abandoned farmland was 258% higher than that of rape field， and 434% higher than that of 3 years abandoned farmland. Soil organic matter and total nitrogen content increased gradually， such as the soil organic matter content of 3 years abandoned farmland being 2124 g/kg and that of abandoned farmland in 21 years being 5266 g/kg. The total nitrogen content of abandoned farmland in 3 years being 105 g/kg and 11 years abandoned farmland being 252 g/kg The total phosphorus reduced with the increase of farming abandoned periods， such as that in 3 years abandoned farmland being 054 g/kg and that in 21 years abandoned farmland being 040 g/kg. The soil microbial biomass carbon content range was 33377-70075 mg/kg，while the soil microbial biomass nitrogen range was 3080-6401 mg/kg Soil microbial biomass carbon was highly significantly correlated （P<001） with soil organic matter， total nitrogen and pH， and was significantly correlated （P<005） with the soil clay content. The soil microbial biomass nitrogen was highly significantly correlated （P<001） with soil organic matter， total nitrogen and bulk density， and was significantly correlated （P<005） with soil pH The analyses and discussion of results indicated that with the hydrological regime and vegetation condition of wetland recovering after farmland abandoning， the soil physicochemical properties were improved towards the native wetland， which promoted soil microbial biomass carbon and nitrogen increasing， but had not reached native wetland condition yet