Changes in soil properties induced by red oak along a fertility gradient

Background and Aims In Europe, the American red oak (Quercus rubra L.) often outcompetes autochthonous species. Its invasiveness is likely to increase with climate change, as it tolerates abiotic stresses better than autochthonous species. Red oak depresses native microbial soil communities due a little palatable litter, and we hypothesized it induces negative feedbacks on biocycling especially in low fertility conditions, where plants take up nutrients as soon as they are made available with litter decomposition. Methods Three areas were selected in Norther Italy along a fertility gradient, and litter degradability and indicators of element biocycling were compared below read oak and autochthonous vegetation. Results Along the fertility gradient, litter degradability changes as a consequence of species shifts (autochthonous to allochthonous vegetation), with the most responsive parameters being: humus forms, C/N of the top mineral horizons, mineralization rates of the partly decomposed Oe horizons. Also the indicators of element biocycling differ between species along the fertility gradient. While the pools of available elements in the first 30 cm did not vary, the availability of elements along the profile and the cation exchange complex resulted more and more different between the two vegetation types moving along the gradient, evidencing how an effective biocycling below red oak was possible only in the most fertile site. Conclusions Our findings demonstrate the negative effects of red oak on plant-soil feedbacks and element availability in forest soils, and we hope these evidences will lead to application containment practices of red oak, especially in low fertility sites.