title: Spartina alterniflora invasion increases soil inorganic nitrogen pools through interactions with tidal subsidies in the Yangtze Estuary, China.
abstract: 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.
authors.affiliation: 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.
authors.forename: Rong Hao
authors.initials: RH
authors.lastname: Peng
authors.forename: Chang Ming
authors.initials: CM
authors.lastname: Fang
authors.forename: Bo
authors.initials: B
authors.lastname: Li
authors.forename: Jia Kuan
authors.initials: JK
authors.lastname: Chen
mesh_terms: D002681:China; D004784:Environmental Monitoring; D058865:Introduced Species; D009584:Nitrogen / Q000032:analysis*; D009586:Nitrogen Fixation; D006109:Poaceae / Q000254:growth & development*; D011157:Population Dynamics; D012987:Soil / Q000737:chemistry*; D014872:Water Movements; D053833:Wetlands
chemical_list: D012987:Soil; D009584:Nitrogen