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坚韧胶衣Collema tenax是干旱和半干旱生态系统中生物土壤结皮的重要组分,其固氮作用对生态系统氮素循环具有重要影响。该地衣生长于温度和水分条件变化剧烈的土壤表面,但在我国北方其固氮活性对冻融的响应尚不清楚。采用乙炔还原法研究了坚韧胶衣固氮活性在不同水分条件下(湿冻组:地衣体含水量>200%干重;干冻组:地衣体含水量<20%干重)和4次冻融处理之间的差异。坚韧胶衣固氮活性为2,371.0-8,701.8nmolC2H4/m2·h,湿冻组固氮活性低于干冻组,对照组固氮活性最高,湿冻组和干冻组的固氮活性(对照的百分比)均与冻融次数呈显著的线性负相关关系(干冻组:R2=0.916,p<0.001;湿冻组:R2=0.965,p<0.001),但湿冻组的斜率绝对值(25.05)明显高于干冻组斜率绝对值(7.60)。结果表明低温对坚韧胶衣固氮活性具有显著抑制作用,干燥条件下坚韧胶衣固氮活性对于低温胁迫的敏感性比地衣体湿润条件下更低,这种较低的敏感性可能是该地衣对我国北方干燥和冷热变化剧烈的气候特点的生理适应策略。
Tough gel coat Collema tenax is an important component of biological soil crusts in arid and semi-arid ecosystems. Its nitrogen fixation plays an important role in ecosystem nitrogen cycling. The lichen grows on the soil surface where the temperature and moisture conditions change drastically, but its response to freeze-thaw in the northern part of China is not clear. Acetylene reduction method was used to study the nitrogen fixation activity of tough gel coat under different water conditions (wet-frozen group:> 200% dry weight of lichen body; dry-frozen group: moisture content of lichen body <20% dry weight) Differences between the treatments. The nitrogen-fixing activity of tough gel coat was 2,371.0-8,701.8nmolC2H4 / m2 · h, the nitrogen fixation activity of wet-freezing group was lower than that of the dry-frozen group, while the nitrogen fixation activity of the control group was the highest. The nitrogen fixation activity (percentage of control) There was a significant linear negative correlation between the number of thawing cycles (R2 = 0.916, p <0.001 for wet-frozen group: R2 = 0.965, p <0.001) Freeze group absolute value of slope (7.60). The results showed that low temperature had a significant inhibitory effect on the nitrogen fixation activity of tough gel coat. Under dry conditions, the nitrogen fixation activity of tough gel coat was less sensitive to low temperature stress than under dry conditions. The lower sensitivity was probably that the lichen had no effect on our country North dry and hot and cold weather characteristics of the physiological adaptation strategy.