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Fate of airborne nitrogen in heathland ecosystems: a 15 N tracer study
Author(s) -
FRIEDRICH UTA,
FALK KIRSTEN,
BAHLMANN ENNO,
MARQUARDT THORBEN,
MEYER HARTMUT,
NIEMEYER THOMAS,
SCHEMMEL SIEGFRIED,
von OHEIMB GODDERT,
HÄRDTLE WERNER
Publication year - 2011
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2010.02322.x
Subject(s) - tracer , sink (geography) , ecosystem , environmental science , environmental chemistry , leaching (pedology) , moss , nitrogen cycle , nitrogen , cycling , soil horizon , ecology , chemistry , soil science , soil water , biology , history , physics , cartography , organic chemistry , archaeology , nuclear physics , geography
In the present study, we analyze the fate of airborne nitrogen in heathland ecosystems (NW Germany) by means of a 15 N tracer experiment. Our objective was to quantify N sequestration and N allocation patterns in an ecosystem that is naturally limited by N, but that has been exposed to airborne N inputs exceeding critical loads for more than 3 decades. We hypothesized that the system has a tendency towards N saturation, which should be indicated by low N sequestration and high N leaching. We analyzed 15 N partitioning (aboveground biomass and soil horizons) and investigated 15 N leaching over 2 years following a 15 N tracer pulse addition. 15 N tracer recovery was 90% and 76% in the first and second year, respectively. Contrary to our expectations, more than 99% of the tracer recovered was sequestered in the biomass and soil, while leaching losses were <0.05% after 2 years. Mosses were the most important short‐term sink for 15 N (64% recovery in the first year), followed by the organic layer. In the second year, the moss layer developed from a sink to a source (23% losses), and soil compartments were the most important sink (gains of 11.2% in the second year). Low 15 N recovery in the current year's shoots of Calluna vulgaris (<2%) indicated minor availability of 15 N tracer sequestered in the organic layer. N partitioning patterns showed that the investigated heaths still have conservative N cycling, even after several decades of high N loads. This finding is mainly attributable to the high immobilization capacities for N of podzols in soil compartments. In the long term, the podzol A‐ and B‐horizons in particular may immobilize considerable amounts of incoming N. Since N compounds of these horizons are not readily bio‐available, podzols have a high potential to withdraw airborne N from the system's N cycle.