Effects of fencing and grazing on soil carbon, nitrogen, phosphorus storage in degraded alkali-saline grassland

The relationships between grazing managements and soil carbon, nitrogen, phosphorus storage and their variations were studied in the degraded alkali-saline grassland by comparative study between fencing and grazing on time series. The results showed that aboveground biomass of degraded grassland decreased by 10.3%, 52.6% and 80.7% after 5, 6 and 8-years continuous grazing, respectively, however, the aboveground biomass of degraded grassland increased by 33.9%, 72.4% and 92.2% after 5, 6 and 8-years fencing, respectively. The underground biomass had similar response with aboveground biomass to grazing managements. Continuous grazing increased the soil pH and bulk density and reduced soil nutrient concentration whereas fencing reduced soil pH and bulk density and increased soil nutrient concentrations. With fencing, organic carbon and total phosphorus storage in surface layer soil gradually increased, however, total nitrogen storage firstly decrease and then increased. With grazing, soil carbon, nitrogen and phosphorus storage in surface layer soil all firstly increased and then decreased. After 5 years for fencing, the soil carbon, nitrogen and phosphorus storage was lower than grazing due to decreasing soil bulk density. The soil organic carbon significantly responded to aboveground biomass which suggested that the aboveground vegetation can be used as an effective indicator for soil carbon storage.