Response of nitrogen dynamics in semi-natural and agricultural grassland soils to experimental variation in tide and salinity |
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Authors: | A Martijn Antheunisse Roos Loeb Marzia Miletto Leon P M Lamers Hendrikus J Laanbroek Jos T A Verhoeven |
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Institution: | (1) Landscape Ecology, Institute of Environmental Biology, Utrecht University, P.O. Box 800.84, 3508 TB Utrecht, The Netherlands;(2) Department of Aquatic Ecology & Environmental Biology, Institute for Water and Wetland Research, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands;(3) Department of Microbial Wetland Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Centre for Limnology, Rijksstraatweg 6, 3631 AC Nieuwersluis, The Netherlands |
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Abstract: | In the framework of rehabilitation efforts to enhance the ecological value of closed-off estuaries, we studied the effects
of restoring a tidal movement and seawater incursion on soil nitrogen conversion rates and vegetation response of semi-natural
and agricultural grasslands in an outdoor mesocosm experiment. Intact soil monoliths including vegetation were collected in
June 2004 on two locations on the shores of the Haringvliet lagoon in the south-western part of the Netherlands, which used
to be a well-developed estuary before closure in 1970. For more than 1 year, soil monoliths were continuously subjected to
a full-factorial combination of tidal treatment stagnant/tidal (0.20 m amplitude)] and water type (freshwater, oligohaline
(salinity = 3)]. Soil, soil moisture and water nitrogen concentrations were monitored for a year, as well as vegetation response
and nitrogen conversion rates in the soil. As expected, nitrogen mineralization rates were enhanced by the tidal treatment
in comparison with the stagnant treatment. Denitrification rates however, were much less affected by tide and were even lower
in the tidal treatments after 3 months in the agricultural grassland soils, implying that in general, soils were more oxic
in the tidal treatments. Oligohaline treatments had virtually no effect on soil nitrogen conversion rates compared to freshwater
treatments. Vegetation performance, however, was lower under saline conditions, especially in the semi-natural grassland.
No further significant differences in response to the tidal and oligohaline treatments were found between the two soils although
they differed strongly in soil characteristics. We conclude that if the rehabilitation measures in the former Haringvliet
estuary are carried out as planned, drastic changes in soil nitrogen processes and vegetation composition will not occur. |
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Keywords: | Denitrification Ecological restoration Estuary Grassland Mesocosm experiment Nitrogen |
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