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| Titel |
Long-term grassland management effects on soil Phosphorus status on rewetted Histosols |
| VerfasserIn |
Sebastian Heller, Jürgen Müller, Manfred Kayser |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250151940
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| Publikation (Nr.) |
 EGU/EGU2017-16713.pdf |
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| Zusammenfassung |
| Since the Neolithic Period, the cultivation of wetlands has played a significant role for the
settlement of Humans northwest Germany. A continuing drainage of the wetlands over the
centuries and an intensified soil cultivation during the last decades has caused irreversible
peat degradation and led to fundamental changes in the landscape. Nowadays, almost
70 % of the 4345 km2 peatland of Lower Saxony is altered by agriculture. For the
revitalization of wetland ecosystems, permanent rewetting is an integral component to
preserve the functions of organic soils and achieve resilient, speciesrich wetlands.
However, permanent rewetting measures are not always feasible. In our study area
at the Osterfeiner Moor, a fen located in the Dümmer lowlands near Osnabrück,
intensive forage cropping areas were converted into extensive permanent grasslands
accompanied by temporary rewetting during winter. This management practice combined
with zero fertilization and a low mowing and grazing intensity aims at mitigating
mineralisation of peat layers and creating a habitat for endangered meadow bird
species.
In this semi-natural ecosystem soil phosphorus (P) dynamics play a crucial role. However,
longterm research results on P availability of degraded and rewetted fens are still lacking.
Thus, we investigated the interaction of different grassland uses and P dynamics in the
soil. We described P depletion of the topsoil over a time scale of 17 years after
the implementation of restoration measures. Our study site comprises of 180 ha
protected grassland divided into 52 management plots. According to the management
system, we divided the plots into meadows, pastures and combinations of cutting
and grazing. The soils in our study area can be characterised as drained organic
soils, WRB: Rheic Sapric Histosols (Drainic), with drastic degradation properties
through moorsh forming processes. Plant-available P (double lactate extraction
method: PDL) was analysed from representative topsoil samples (0-10 cm) from all
fields.
During the first four years of extensive grassland use, changes in PDL were negligible.
Values of PDL reached an arithmetic mean of about 70 mg l1, while in the last 13 years,
mean PDL decreased to less than 44 mg l1. Changes in PDL status in soil were significantly
depending on time and type of grassland management. After 17 years we found highest PDL
concentrations in the soil in pastures (44 mg l1) while meadow grassland had a lower PDL
concentration of 23 mg l1. Fields with a combination of cutting and grazing had a
PDL concentration of 36 mg l1.
Generally, on grazed fields, the majority of nutrients returns to the soil through
excrements. Therefore, on permanent pastures, even with no fertiliser applications or feeding
supplements to the grazing livestock, concentrations of PDL in the soil will only slowly
decline. On the other hand, nutrient flux via biomass production on meadows cause stronger
depletion of PDL in the longterm. These results have consequences for nutrient
management of extensive grassland on rewetted fens in practice and in turn has an
effect on botanical composition, feed quality and on the abundance of soil fauna. |
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