Coastal Ecosystems Research Station of the Yangtze River Estuary, Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, The Institute of Biodiversity Science, Fudan University, Shanghai 200433, China.
Oecologia. 2011 Mar;165(3):797-807. doi: 10.1007/s00442-010-1887-7. Epub 2011 Jan 4.
Invasive alien plants increase both plant N and soil inorganic N pools in many terrestrial ecosystems. This is believed to be the result of altered plant-soil-microbe feedbacks that accelerate N cycling. However, it may also be due to the greater ability of invasive species to uptake lateral N subsidies that can modify ecosystem N dynamics. We conducted manipulative field experiments to determine the impact of smooth cordgrass (Spartina alterniflora) invasion on the N cycling of salt marsh ecosystems in the Yangtze Estuary, China. The results showed that the aboveground plant N and soil inorganic N pools in S. alterniflora marshes, 14.39 and 3.16 g N m(-2), were significantly higher than those in native common reed (Phragmites australis) marshes, 11.61 and 2.29 g N m(-2). These increases after invasion were explained by a significantly higher uptake of dissolved inorganic N (DIN) from tidal subsidies in S. alterniflora marshes (6.59 g N m(-2)) than from those in P. australis marshes (1.61 g N m(-2)), and not by soil organic N mineralization, which was not significantly different between S. alterniflora (6.45 g N m(-2)) and P. australis marshes (6.84 g N m(-2)) during the growing season. Our study indicated that the ecosystem engineering effects of S. alterniflora, which increases the interception of external N input, can be an alternative mechanism that increases plant N and soil inorganic N pools--especially in ecosystems with ample anthropogenic N subsidies, such as the coastal wetlands of China.
入侵的外来植物会增加许多陆地生态系统中的植物氮和土壤无机氮库。这被认为是改变植物-土壤-微生物反馈的结果，这种反馈加速了氮循环。然而，这也可能是由于入侵物种吸收侧向氮补贴的能力更强，从而改变了生态系统的氮动态。我们进行了控制性野外实验，以确定光滑大米草（Spartina alterniflora）入侵对中国长江口盐沼生态系统氮循环的影响。结果表明，光滑大米草沼泽地上植物氮和土壤无机氮库分别为 14.39 和 3.16 g N m(-2)，明显高于本地芦苇（Phragmites australis）沼泽地上的氮库，分别为 11.61 和 2.29 g N m(-2)。入侵后这些氮的增加可以通过光滑大米草沼泽地从潮汐补贴中吸收的溶解无机氮（DIN）（6.59 g N m(-2)) 明显高于芦苇沼泽地（1.61 g N m(-2)) 来解释，而不是由于土壤有机氮矿化，在生长季节，光滑大米草（6.45 g N m(-2)) 和芦苇（6.84 g N m(-2)) 之间的矿化没有显著差异。我们的研究表明，光滑大米草的生态系统工程效应增加了对外来氮输入的截留，这可能是一种增加植物氮和土壤无机氮库的替代机制——特别是在有充足人为氮补贴的生态系统中，如中国沿海湿地。
