外源氮输入对互花米草生长及叶特征的影响

入侵种互花米草（Spartina alterniflora）是滨海盐沼湿地的多年生草本植物,研究人类活动引起的外源氮输入对其生长的影响有助于了解滨海湿地生态系统结构和功能的未来变化趋势。运用随机区组试验设计方法,模拟海滩水分条件（间歇淹水和持续淹水）,研究了互花米草的地上部生物量、叶片光合特征以及形态特征对外源氮输入的响应。结果表明：互花米草地上部生物量在施氮条件下显著增加,且在土壤处于间歇淹水状态时表现更为明显;施氮条件下植株分蘖数比对照处理分别增加了60.0%和60.2%,是引起地上部生物量增加的主要原因。施加氮素促进了互花米草叶片的生长,叶面积、叶数、叶长和叶宽均显著增加,而叶数的变化是导致植物叶面积增加的主要因素。外源氮输入促进了互花米草叶绿素含量的增加,而对净光合速率的季节变化特征无明显影响。持续淹水处理的植物地上部生物量、生长速率、分蘖数、净光合速率和叶面积均低于间歇淹水处理,说明持续淹水状态对互花米草生长造成了一定的抑制作用。

Influence of exogenous N import on growth and leaf character of Spartina alterniflora

Spartina alterniflora,has become an invasive halophyte in China.Investigating effect of exogenous N on its growth may contribute to understanding variation trend of structure and function of ecosystem in littoral wetland.We studied responses of biomass of Spartina alterniflora,photosynthesis and morphology character of leaves,to exogenous N under two water condition.The aboveground biomass significantly increased under N application,and this trend showed be more pronounced under intermittent flood condition compared to persistent flood condition.Tillering number increased by 60.0% and 60.2% under N import,which profoundly resulted in enhancement of aboveground biomass.N application significantly boosted leaf area,leaf number,leaf length and leaf width,and variation of leaf number was the major factor for increase of leaf area.Chlorophyll content enhanced significantly under N import,while seasonal pattern of net photosynthetic rate variation were not significantly influenced.The measured growth index always decreased under persistent flood condition,indicating that persistent flooding inhibited growth of Spartina alterniflora.