Trophic interactions as indicators of ecosystem regeneration in disturbed grassland : a stable isotope approach
Stable isotope techniques were used to identify regeneration patterns in the trophic structure of the reassembling communities in order to describe the development of a disturbed grassland ecosystem (Steudnitz) that had been subjected to anthropogenic pollution for more than 30 years. Mean values of the frequency distribution of [delta]15N differences between epigeic arthropods and their diet indicated the adjustment of food web components to their food sources with trophic level enrichments between 3 and 4 [Promille] ('3.4[Promille]-rule') at the most recovered sites. Temporal changes of the animal 15N signatures reflected the development of the food web at the four differently impacted sites. Similar dynamics, i.e., minimal variations between species representing different trophic levels, imply functional stability of the trophic relationships. Moreover, the difference between soil and animal [delta]15N values mirrored the level of functional integration between soil food web and aboveground food web, and, parallel development of the [delta]15N values of epigeic species relative to those of the soil indicated the attainment of stable relations between aboveground and belowground processes. The study highlighted that - due to its 'isotopic memory' - substantial information to understand the functioning of terrestrial ecosystems can be found in the soil.