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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。
The algae and moss crusts developed in the sand-fixing vegetation area and adjacent natural vegetation southeastern margin of the Tengger Desert were studied. OTCs with different specifications were used to study the effect of winter low temperature and short-term simulated warming on their nitrogen fixation activity. The results showed that the OTCs with different specifications had a temperature rise of about 1 ℃ in winter and a temperature increase of about 3.2 ℃ in different depths. In winter, algal and moss crusts had nitrogen fixation activity under wet conditions , The average nitrogen fixation activities were 1.2 × 104 and 0.4 × 104nmolC2H4 · m-2 · h-1, respectively, and the nitrogen fixation activity of algal crusts was significantly higher than that of moss crusts (P <0.01). The algal and moss crusts Nitrogen fixation activity was significantly and positively correlated with air temperature during incubation (P <0.001), and also positively correlated with precipitation before the experiment (P <0.001). In low temperature and humid environment, the damage of nitrogenase system caused by intracellular ice formation in crusting organisms may be the main reason for the decrease of nitrogen fixation activity in winter crusts. Winter temperature increase can promote the activity of nitrogen fixation in crusts. This study shows that winter warming can promote the contribution of biological soil crusts to nitrogen in the regional ecosystem in the context of changes in global warming and precipitation patterns in the future.