In situ soil net nitrogen mineralization in coastal salt marshes (Suaeda salsa) with different flooding periods in a Chinese estuary |
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| Affiliation: | 1. Finnish Environment Institute, P.O. Box 111, FI-80101 Joensuu, Finland;2. Department of Geographical and Historical Studies, University of Eastern Finland, 80101 Joensuu, Finland;3. Finnish Environment Institute, P.O. Box 140, FI-00251 Helsinki, Finland;4. Natural Resources Institute Finland, 80101 Joensuu, Finland;1. State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, PR China;2. Fujian Forestry Survey and Planning Institute, Fujian 350003, PR China;3. Apprisal Center for Environment and Engineering, Ministry of Environmental Protection, Beijing 100012, PR China;1. Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China;2. University of the Chinese Academy of Sciences, Beijing 100049, China;1. INRA, UR 1158 AgroImpact, site de Laon, F-02000 Barenton-Bugny, France;2. AUREA, F-45160 Ardon, France;3. ARVALIS - Institut du Végétal, F-91720 Boigneville, France;4. Terres Inovia, Centre INRA de Toulouse, CS 52627, F-31326 Castanet-Tolosan Cedex, France;5. INRA, UMR INRA/INPT 1248 AGIR, Auzeville, CS 52627, F-31326 Castanet-Tolosan Cedex, France;1. State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200241, China;2. Key Laboratory of Geographic Information Science (Ministry of Education), East China Normal University, Shanghai, 200241, China;3. School of Geographic Sciences, East China Normal University, Shanghai, 200241, China |
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| Abstract: | Flooding periods can be one of the most important factors influencing nitrogen (N) biogeochemical processes in wetlands ecosystem. We conducted a field study using in situ incubation method to investigate the seasonal dynamics of soil net N mineralization in three coastal salt marshes (Suaeda salsa) with different flooding periods (i.e., short-term (STF), seasonal (SF), and tidal (TF) flooding wetland) in the Yellow River Delta. Selected soil inorganic N pools (ammonium, nitrate and inorganic N) and N transformation (mineralization, nitrification and ammonification) rates in the top 0–10 cm soils were repeatedly quantified from April to October. Clear seasonal patterns in inorganic N pools and transformation rates were observed in accord with the seasonal variations of temperature and moisture. Generally, higher levels of soil inorganic nitrogen, ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3－-N) occurred in the early-growing season (April), and NH4+-N contents got a small accumulative peak in midsummer (September). The lower rates (negative) of net mineralization (Rmin), nitrification (Rnit) and ammonification (Ramm) were observed in the early-growing season (April–June) and fall (September–October), whereas higher values (positive) in midsummer (August–September). Flooding had a significant influence on inorganic N pools (except for NH4+-N) and transformation rates (p < 0.05). Rmin values in SF wetland were significantly higher in the August-September period than those in other incubation periods. Rnit values in TF wetland exhibited a small variation and the highest value occured in the June–August period. The results of principal component analysis showed that soil samples were clearly divided into two groups before and after flow-sediment regulation. After flooding events, the Rmin and Ramm values generally increased in the three wetlands, whereas a significant decrease in Rnit values was observed in SF wetland (p < 0.05), thus the differences in NO3－-N among these wetlands were eliminated. These results suggested that seasonal variations in temperature and moisture are important factors influencing inorganic N pools and transformation rates. |
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| Keywords: | Nitrogen mineralization Flooding periods Soil inorganic nitrogen Coastal wetlands |
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