Data from: Increased nitrogen input enhances Kandelia obovata seedling growth in the presence of invasive Spartina alterniflora in subtropical regions of China

Mangroves in China are severely affected by the rapid invasion of the non-native species Spartina alterniflora. Although many studies have addressed the possible impacts of S. alterniflora on the performance of mangrove seedlings, how excessive nitrogen (N) input due to eutrophication affects the interactions between mangrove species and S. alterniflora remains unknown. Here, we report the results from a mesocosm experiment using seedlings of the native mangrove species Kandelia obovata and the exotic S. alterniflora grown in monoculture and mixed culture under no nitrogen addition and nitrogen (N) addition treatments for 18 months. Without N addition, the presence of S. alterniflora inhibited the growth of K. obovata seedlings. Excessive N addition significantly increased the growth rate of K. obovata in both cultures. However, the positive and significantly increasing relative interaction intensity index under excessive N input suggested that the invasion of S. alterniflora could favour the growth of K. obovata under eutrophication conditions. Our results imply that excessive N input in southeastern China can increase the competitive ability of mangrove seedlings against invasive S. alterniflora.中国红树林正受到外来物种互花米草（Spartina alterniflora）快速入侵的严重影响。尽管已有多项研究探讨了互花米草对红树林幼苗生长表现的潜在影响，但富营养化引发的过量氮（N）输入如何影响红树林物种与互花米草之间的种间相互作用，目前仍不明晰。本研究依托一项中型受控生态系统实验（mesocosm experiment），以本土红树物种秋茄（Kandelia obovata）与外来种互花米草的幼苗为实验材料，设置单种、混种两种种植模式，并施加无氮添加、氮添加两种处理，持续培养18个月，对实验结果进行了报道。在无氮添加的条件下，互花米草的存在会抑制秋茄幼苗的生长。过量氮输入则显著提升了两种种植模式下秋茄的生长速率。然而，过量氮输入下相对相互作用强度指数呈现正向且显著上升的趋势，这表明在富营养化条件下，互花米草的入侵反而可能促进秋茄的生长。本研究结果暗示，中国东南沿海地区的过量氮输入，能够提升红树林幼苗对抗入侵种互花米草的竞争能力。