中文摘要：

地卷目地衣是对许多生态系统的氮素循环具有重要影响的固氮类群,但其固氮活性的种间差异研究甚少。将不同产地和不同馆藏时间的12种地卷目地衣于相同条件下培养,即：亚石胶衣Collema subflaccidum、亚黑胶衣C.subnigrescens、坚韧胶衣C.tenax、裸果猫耳衣Leptogium hildenbrandii、猫耳衣L.menziesii、柄猫耳衣L.pedicellatum、土星猫耳衣L.saturninum、黑猫耳衣L.trichophorum、犬地卷Peltigera canina、分指地卷P.didactyla、裂芽地卷P.praetextata和地卷P.rufescens。以乙炔还原法（acetylene reduction assay）于培养1d、10d和15d测定其固氮活性,结果显示所有地衣的固氮活性在培养10d与15d之间差异不显著,表明经过至多10d的培养后地衣固氮活性即可完全恢复;培养10d和15d的固氮活性平均值表现出显著的种间差异（P〈0.001）：黑猫耳衣Leptogium trichophorum固氮活性最高[（4.532±0.368）μmol C2H4/gdw·h],约为犬地卷Peltigera canina的2倍[（2.349±0.223）μmol C2H4/gdw·h];其他10种地衣固氮活性大致相近。显示地衣固氮作用的可塑性较大,是地衣具有较强适应能力的又一例证。

英文摘要：

The order Peltigerales is an important group of N-fixing lichens that are essential for ecosystem N cycling in many terrestrial ecosystems.But differences in N-fixing activity among species are not well understood at present.Twelve peltigeralean species collected in different localities and subjected to various desiccation durations,namely Collema subflaccidum,C.subnigrescens,C.tenax,Leptogium hildenbrandii,L.menziesii,L.pedicellatum,L.saturninum,L.trichophorum,Peltigera canina,P.didactyla,P.praetextata and P.rufescens,were cultured in the same condition.N-fixing activity was measured using acetylene reduction assay after 1d,10d and 15d cultivation.No significant differences in N-fixing activity for all lichens were found between 10d and 15d cultivation,suggesting N-fixing activity for lichens was fully recovered after 10d cultivation.A significant difference in N-fixing activity among species was found in terms of mean N-fixing activity averaged over 10d and 15d cultivations （P0.001）,with the highest value for Leptogium trichophorum [（4.532±0.368）μmol C2H4/gdw·h] which is about 2 times higher than that for Peltigera canina [（2.349±0.223）μmol C2H4/gdw·h].N-fixing activity of the other 10 lichens was roughly similar （2.635-3.379μmol C2H4/gdw·h）.These results show lichens have high N fixation plasticity,which can be an evidence for the adaption of lichens to fluctuating environment conditions.