摘要
坚韧胶衣Collema tenax和分指地卷Peltigera didactyla是分布于我国北方干旱和半干旱草原中的两种固氮地衣,对生态系统氮素循环具有重要影响,其生理活性对土壤水分条件比较敏感。目前,干旱持续时间对该区域中地衣固氮活性的影响尚不清楚。本文调查了一个克氏针茅Stipa krylovii草原生态系统中坚韧胶衣和分指地卷的盖度,采用乙炔还原法研究了不同干旱持续时间(分别为0、1、2、4、8和16d)对两种地衣固氮活性的影响。结果表明,坚韧胶衣盖度(3.26±1.24%)显著高于分指地卷(0.02±0.07%)(p<0.01);在绝大多数干旱持续时间处理下,两种地衣之间的固氮活性差异并不显著,且均随干旱持续时间延长而呈S形下降。不超过2d的干旱时间并不引起地衣固氮活性的显著变化,4d的干旱时间导致坚韧胶衣和分指地卷固氮活性分别下降了34%和54%,干旱持续8d导致两种地衣固氮活性降幅达90%,16d的干旱使二者降幅均超过99%。表明干旱对坚韧胶衣和分指地卷固氮活性的抑制作用随干旱持续时间的延长而增强。干旱对地衣固氮作用的负效应可能与地衣体内光合产物和能量水平、复水至表达固氮活性之间的延迟时间和达到最高固氮活性的延迟时间有关。
Collema tenax and Peltigera didactyla are N-fixing lichens in arid and semiarid grasslands, where water and nitrogenavailability are essential factors influencing ecosystem structure and functions. The response of N-fixing activity of lichens to drought in temperate grasslands of China has received little attention in the past ecological studies. The purpose of the present study was to investigate the effects of drought duration on N fixation of C. tenax and P. didactyla by measuring potential N-fixing activity of both lichens that have been subjected to drought for 0, 1, 2, 4, 8 and 16 days. All samples were collected from a semiarid grassland in Inner Mongolia and N-fixing activity was measured using acetylene reduction assay. Most drought duration treatments yielded insignificant differences in N-fixing activity between species. N-fixing activity of both C. tenax and P. didactyla sigmoidally decreased with drought duration （R2 = 0.9996 and R2 = 0.9954, respectively）. These results show an inhibitory effect of drought on N fixation for both lichens. This effect can be intensified by prolonged drought duration. No significant changes in N fixation of both lichens were found in the drought duration less than 2 days. However, a 4-day drought resulted in a significant decline in N-fixing activity of C. tenax and P. didactyla （decreased by 34% and 54%, respectively）. N-fixing activity of both lichens decreased by up to 90% when being dried for 8 days, and declined by more than 99% in 16-day drought duration. The negative effects of drought on N fixation of both lichens could be attributable to the low levels of photosynthate and energy, and to the lag time after rewetting before N-fixation was initiated and before maximal N-fixing activity was reached.
出处
《菌物学报》
CAS
CSCD
北大核心
2009年第6期783-789,共7页
Mycosystema
基金
中国科学院创新群体项目(No.30521002)
国家自然科学基金(No.30700107)
关键词
地衣
水分
乙炔还原法
lichen, water, acetylene reduction assay
