15N natural abundance during early and late succession in a middle-European dry acidic grassland.
delta(15)N and total nitrogen content of above- and belowground tissues of 13 plant species from two successional stages (open pioneer community and ruderal grass stage) of a dry acidic grassland in Southern Germany were analysed, in order to evaluate whether resource use partitioning by niche separation and N input by N(2)-fixing legumes are potential determinants for species coexistence and successional changes. Within each stage, plants from plots with different legume cover were compared. Soil inorganic N content, total plant biomass and delta(15)N values of bulk plant material were significantly lower in the pioneer stage than in the ruderal grass community. The observed delta(15)N differences were rather species- than site-specific. Within both stages, there were also species-specific differences in isotopic composition between above- and belowground plant dry matter. Species-specific delta(15)N signatures may theoretically be explained by (i) isotopic fractionation during microbial-mediated soil N transformations; (ii) isotopic fractionation during plant N uptake or fractionation during plant-mycorrhiza transfer processes; (iii) differences in metabolic pathways and isotopic fractionation within the plant; or (iv) partitioning of available N resources (or pools) among plant groups or differential use of the same resources by different species, which seems to be the most probable route in the present case. A significant influence of N(2)-fixing legumes on the N balance of the surrounding plant community was not detectable. This was confirmed by the results of an independent in situ removal experiment, showing that after 3 years there were no measurable differences in the frequency distribution between plots with and without N(2)-fixing legumes.
Beyschlag
W
W
Department of Experimental and Systems Ecology, University of Bielefeld, Bielefeld, Germany. w.beyschlag@uni-bielefeld.de
Hanisch
S
S
Friedrich
S
S
Jentsch
A
A
Werner
C
C
D017753:Ecosystem; D007887:Fabaceae / Q000378:metabolism*; D005858:Germany; D006863:Hydrogen-Ion Concentration; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000378:metabolism; D006109:Poaceae / Q000378:metabolism*; D013997:Time Factors
D009587:Nitrogen Isotopes; D009584:Nitrogen