Iron-rich dune grasslands: relations between soil organic matter and sorption of Fe and P.
Effects of high atmospheric nitrogen-deposition partly depend on availability of phosphate. Lime-poor, but iron-rich dune grasslands are supposedly protected from grass-encroachment, due to P-fixation in iron phosphate. However, in iron-rich Dutch hinterdunes, dunes have low, but dry former beach plains high grass-encroachment. To test whether these zones differ in nutrient availability, and whether this changed with duration of grass-encroachment, we measured net N-mineralization, microbial characteristics and different fractions of P and Fe from pioneer and shortgrass to tallgrass stages approximately 10, 20 and >25 years old. N-mineralization did not differ between zones, but increased in older tallgrass stages in the organic layer. P-availability was significantly lower in the low grass-encroachment zone, with SOM values below 3% and mineral Fe above 40% allowing for P-fixation in iron phosphates. In the high grass-encroachment zone, however, P-availability increased, because SOM increased and Fe became incorporated in organic matter complexes, with more reversible P-sorption.
Kooijman
A M
AM
Institute of Biodiversity and Ecosystem Dynamics, Paleoecology & Landscape Ecology, University of Amsterdam, Amsterdam, The Netherlands. a.m.kooijman@uva.nl
Lubbers
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I
van Til
M
M
D000327:Adsorption; D006812:Humic Substances / Q000032:analysis*; D007501:Iron / Q000737:chemistry / Q000378:metabolism*; D010758:Phosphorus / Q000737:chemistry / Q000378:metabolism*; D006109:Poaceae / Q000737:chemistry / Q000378:metabolism*; D012987:Soil / Q000737:chemistry*
D006812:Humic Substances; D012987:Soil; D010758:Phosphorus; D007501:Iron