Grazing by red deer counteracts atmospheric nutrient deposition in semi-natural open habitats

Abstract

Semi-natural habitats are vulnerable to eutrophication, which can result from atmospheric deposition. Maintaining habitat-specific nutrient conditions despite atmospheric inputs is a challenge for conservation. Grazing wild red deer (Cervus elaphus) is suggested as an alternative management measure for open habitats, but effects of red deer on nutrient dynamics have not yet been evaluated. To quantify import and export of nitrogen (N) and phosphorus (P) by red deer, we collected data on vegetation productivity, forage removal, dung quantity, and nutrient concentrations from permanently marked plots in two habitat types (European dry heaths, lowland hay meadows) on a military training area in Germany.
The annual nutrient export of N and P by red deer grazing was notably higher than the nutrient import through excreta in both habitats. Net nutrient removal averaged 13.9 and 29.5 kg N ha-1 yr-1 and 1.1 and 3.3 kg P ha-1 yr-1 in heathlands and grasslands, respectively, thus exceeding estimated values for local atmospheric deposition. In consequence, red deer grazing can mitigate the effects of atmospheric nutrient deposition in semi-natural open habitats.