In the research, acetylene reduction was applied to investigate the nitrogenase activity of algal crusts in artificial vegetation areas with different restoration time and natural vegetation area, as well as their responses to simulated precipitation and temperature. Results showed that the nitrogenase activity of algal crusts varied in a range of 4.31~16.6 mmol·m-2·h-1 in the region. Significantly positive correlation was observed between nitrogenase activity and restoration time in the artificial vegetation area, the nitrogenase activity in natural vegetation area was significantly lower than in 52-year-restoration artificial vegetation area, while profoundly higher than 16-year-restoration artificial vegetation area. Significantly positive correlations between nitrogenase activity and Chl a, as well as with crust cover were observed. The nitrogenase activity increased dramatically with increase of simulated precipitation when the precipitation amount was less than 1.1 mm, while when the precipitation was from 1.1 mm to 5 mm, the nitrogenase activity gradually showed steady status. The nitrogenase activity of different vegetation areas showed similar pattern with air temperature. All nitrogenase activity showed a higher value under the air temperature of 24 ℃ compared with 13 ℃ in the artificial vegetation area.

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The variation patterns of nitrogenase activity of algal crusts at artificial vegetation areas and natural vegetation subjected to simulated precipitation