Abstract:

Spartina alterniflora, an alien species, has invaded and severely harmed the intertidal coast with different effects on the ecology, landscape and economy in China. Therefore, it is urgent to study the invasion mechanism of S. alterniflora to effectively control it. Yellow River Delta (YRD) is one of the most affected areas by S. alterniflora in North China. In this study, a transplanting experiment of S. alterniflora was carried out in the intertidal zone of YRD. In June 2019, the seedlings (seed germinated seedlings) and clonal ramets (rhizome germinated seedlings) of S. alterniflora were transplanted to different locations with elevations ranging from 65.5 cm to 114.7 cm. To detect the effect of different elevation on the growth and expansion of S. alterniflora seedlings in the intertidal zone and the elevation threshold for S. alterniflora survival, regular investigations of the growth status of S. alterniflora, tide and soil properties at the transplanting sites were conducted. The results showed that, (1) With the increase of elevation, there were significant differences in the duration and depth of tidal flooding in the intertidal zone of YRD. (2) In YRD, the main factors affecting the growth and reproduction of S. alterniflora were the average flooding time, average flooding depth and soil salinity resulting from the combined action of elevation and tide. (3) In general, the growth status of seedlings and clonal ramets of S. alterniflora became worse with the increasing elevation, the seedlings could survive in the Suaeda salsa dominant area, and clonal ramets could survive in areas dominated by Phragmites australis and Tamarix ramosissima at higher elevation. And (4) along the direction from sea to land, S. alterniflora could rapidly expand to the Suaeda salsa dominant area in a short time, and after a long term, S. alterniflora might invade to Phragmites australis or even Tamarix ramosima dominant zones. Therefore, the control of S. alterniflora in northern China is urgent. Firstly, the sexual reproduction of S. alterniflora seeds should be effectively controlled to limit or prevent its long-distance expansion by the seeds. Secondly, the control pace of S. alterniflora should be accelerated. Otherwise, after long-term adaptation, S. alterniflora is likely to expand further to the land, leading to direct competition with the native vegetation Phragmites australis and Tamarix ramosissima, and strengthening its threat to intertidal ecosystems.

Key words: Spartina alterniflora, Yellow River Delta, intertidal zone, sexual reproduction, asexual reproduction

摘要：

外来物种互花米草（Spartina alterniflora）入侵中国后,对潮间带滨海湿地的生态环境危害巨大,对河口湿地生态、景观、经济等方面均有不同程度影响,研究其入侵机制对有效防治互花米草是不可或缺的。黄河三角洲是中国北方受互花米草侵害最严重的地区之一。该研究在黄河三角洲潮间带开展互花米草移栽试验,2019年6月,在由海向陆方向上,把互花米草实生苗（种子萌发苗）与克隆苗（根茎萌发苗）移栽至高程范围为65.5—114.7 cm的不同地点,定期调查移栽点互花米草生长状况,同时进行潮汐与土壤性质监测,揭示潮间带不同高程对互花米草幼苗生长与扩散的影响,确定互花米草存活的高程阈值。结果表明：（1）随着高程升高,黄河三角洲潮间带的潮汐淹水时长和淹水深度有显著差异;（2）在黄河三角洲,影响互花米草生长与繁殖的主要环境因素为高程和潮汐共同作用的平均淹水时间、平均淹水深度和土壤盐度;（3）总体而言,互花米草实生苗与克隆苗的生长状况随高程升高而变差,实生苗可在盐地碱蓬分布区存活,克隆苗可在高程更高的芦苇和柽柳分布区存活;（4）在由海向陆方向上,短期内互花米草可快速扩散至盐地碱蓬分布区,经过长期适应后,互花米草可能扩散至芦苇分布区甚至柽柳分布区。因此,中国北方互花米草防控刻不容缓,首先应有效控制互花米草种子的有性繁殖,限制或阻止其通过种子进行远距离扩散,其次,应加快互花米草控制步伐,否则,经过长期适应之后,互花米草很可能继续向陆地方向扩张,与本土植被芦苇和柽柳产生直接竞争,扩大其对潮间带生态系统的威胁。

关键词: 互花米草, 黄河三角洲, 潮间带, 有性繁殖, 无性繁殖