冬季低温及模拟升温对生物土壤结皮固氮活性的影响

以腾格里沙漠东南缘固沙植被区和相邻天然植被区发育的藻类和藓类结皮为研究对象,采用不同规格的OTCs研究了冬季低温及短期模拟升温对其固氮活性的影响。结果表明:不同规格的OTCs装置冬季全天气温升温幅度在1℃左右,不同深度土层升温幅度更加明显,约为3.2℃;冬季试验期,湿润条件下藻类和藓类结皮均具有固氮活性,平均固氮活性分别为1.2×104和0.4×104nmolC2H4·m-2·h-1,藻类结皮的固氮活性显著高于藓类结皮(P<0.01);试验期藻类和藓类结皮的固氮活性均与培养期气温显著正相关(P<0.001),与试验前3d降水量也呈显著正相关(P<0.001)。低温湿润冷冻环境下,结皮生物体胞内冰晶形成而导致的固氮酶体系受损可能是造成冬季结皮固氮活性降低的主要原因,冬季升温能促进结皮固氮活性的提高。本研究表明,在未来全球变暖和降水格局变化背景下,冬季升温能促进生物土壤结皮对区域生态系统的氮贡献。

Effects of wintertime low temperature and simulated warming on nitrogen-fixing activity of soil biocrusts

Taking the soil algal and moss crusts in natural and re-vegetated areas at the southeast edge of Tengger Desert as test objects and by using different types of OTC,this paper studied the nitrogen-fixing activities of the crusts under effects of wintertime low temperature and simulated warming.In the OTCs,the increment of wintertime daily air temperature was about 1 ℃,and that of the soil temperature at different depths was about 3.2 ℃.During the experimental period,the average nitrogen-fixing activity of algae crust was 1.2×104 nmol C2H4·m-2·h-1,which was significantly higher than that of moss crust(0.4×104 nmol C2H4·m-2·h).The nitrogen-fixing activities of algal and moss crusts were significantly positively correlated with the air temperature in whole experimental period,and with the precipitation amount three days before the experiment.Under the low temperature,wet,and freezing conditions in wintertime,the damaged nitrogen-fixing enzyme system because of the intracellular ice formation of crust organisms could be the main reason for the decline of the crust’s nitrogen-fixing activities,while warming could promote the crust’s nitrogen-fixing activities.Our study suggested that under the background of future global warming and precipitation pattern change,the increase of air temperature in wintertime could promote the nitrogen contribution of soil biocrusts to arid area ecosystems.