温带荒漠区藻结皮固氮活性沿时间序列的变化

利用乙炔还原法,测定腾格里沙漠东南缘沙坡头地区不同年代建植的人工植被固沙区和相邻自然植被区藻结皮的固氮活性及其对水分和温度的响应特征。结果表明,不同植被区藻结皮的固氮活性在4.31~16.6 mmol·m-2·h-1;人工植被区藻结皮的固氮活性与植被恢复时间呈显著的正相关关系,自然植被区藻结皮的固氮活性显著小于52龄人工植被区,但显著高于16龄人工植被区;藻结皮的固氮活性与叶绿素a含量和盖度呈显著正相关关系;模拟降雨量<1.1~1.5 mm,不同人工植被区和自然植被区藻结皮的固氮活性随着模拟降雨量的增加而急剧增加,但当1.1~1.5 mm<模拟降雨量<5 mm时,藻结皮的固氮活性随模拟降雨量的增加无显著增加;不同植被区藻结皮的固氮活性与温度的关系表现出一致的变化趋势,当温度为13 ℃时,藻结皮的固氮活性显著低于最热月的均温(24 ℃)。

Nitrogenase Activity Chronosequence of Algal Crusts in Temperate Desert Region

In this study,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\5m-2\5h-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.