engleski

Nutrient leaching heterogeneity across a dynamic floodplain mosaic

Abstract: Riverine floodplains are a mosaic of aquatic, semi-aquatic and terrestrial habitats. While spatially distinct, these habitats are well connected by flows of carbon and nutrients, and thus the ecological processes occurring in one habitat have ramifications for others. The aim of this study was to: 1) compare nutrient and organic matter leaching, a key process in riverine ecosystems, across diverse floodplain-habitat types ; 2) assess the role of inundation duration and temperature on release rates ; 3) determine leaf litter contribution to nutrient leaching. In the Tagliamento floodplain (NE Italy), we collected replicated samples of leaf litter accumulations (Populus nigra L.) and sediments form various aquatic and terrestrial habitat types. Samples were dried at air-temperature and leaching experiments were conducted under controlled laboratory conditions. Using artificial river water we simulated leaching at three temperatures (4, 12, 25°C) and 12, 36 and 96hrs of immersion. The POC, TN and TP contents in leaves were several times higher then in sediments. Total leachets for DOC, TP and TN were significantly higher in leaves compared to sediments. Relative leachates (per total of respective element in sample) only for DOC and TP. Leaching rates ranged from 0.04 (gravel) to 59.81 (leaves) mg DOC/g POC ; 7.54 (ponds) to 59.47 (leaves) mg N/g N and 0.13 (ponds) to 134.81 (leaves) mg P/g P. Leaching of DP and DOC was negatively related to temperature and inundation duration. Leaching of NO2 was positively related to both inundation duration and temperature. In terrestrial habitats, leaching of DN and NH4 significantly increased with longer inundation duration. From these results we conclude: that leaf litter is the key source for C and P within the floodplain contributing with 98% to total floodplain release ; DOC may be promptly utilized by biota (or adsorbed), while NH4 in aquatic habitats is either flushed downstream or biologically transformed to other N ions.

ispiranje; Tagliamento; poplavna ravnica

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