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The vitality of European forests continues to decline due to new pests and diseases, climate-change related disturbances and high loads of atmospheric nitrogen deposition. Deteriorating soil health is a major factor underpinning the low vitality of West-European forests. Selecting tree species with soil ameliorative traits is proposed as an avenue to counteract soil acidification and improve overall forest vitality. Here we evaluate the impact of black cherry (Prunus serotina Ehrh.), a known rich litter species, on the vitality of neighboring pedunculate oak (Quercus robur L.) in ten mixed forests on sand in Germany, Belgium and the Netherlands. We found that black cherry admixture increases foliar N and P to a surplus whereas it causes deficiencies in foliar Mg, thereby resulting in an overall negative effect on oak foliar nutrient concentrations. Contrary, defoliation of oak leaves by herbivory decreases with the proximity of black cherry. Using structural equation modelling (SEM), we tested the hypothesized 'improved soil health' pathway. Our analyses showed that black cherry admixture leads to lower accumulation in the humus layer, resulting in higher soil base saturation which has a positive effect on foliar Ca yet a negative effect on total chlorophyll. Moreover, the SEM illustrated that herbivory of oak leaves decreases when black cherry is admixed, both via dilution and improved soil health. Indirect effects of black cherry on oak vitality via "improved soil health" in our SEM are however small in comparison to direct relations. Hence, our study showed that the combined positive and negative impacts of black cherry on oak vitality are limited, which tempers the potential benefits of using the rich litter species to counteract oak decline via improved soil health - yet, the concern of black cherry as an invasive alien species negatively affecting the vitality of mature pedunculate oak trees may also be exaggerated. [ABSTRACT FROM AUTHOR]

Black Cherry (Prunus serotina Ehrh.) is a broadleaved tree species native to Northern- and Central-America which was introduced in many other parts of the world, especially in European countries. In many places it has been classified as an invasive species and its management is subject to hotly debates. This review provides an overview of the existing knowledge on the ecology and management of this species in its native and non-native range, with special focus on Europe. Based on the reviewed literature, Black Cherry is a fast-growing and light-demanding forest gap specialist, which tolerates most soil conditions. Depending on the forest site, the species has an either positive or negative influence on soil conditions and nutrient cycling. It is able to alter the forest species composition and site conditions in its non-native range, necessitating control measures in nature conservation areas. However, the elimination of this species has been unsuccessful. Instead, the silvicultural integration of Black Cherry may provide a cost- and labor-effective alternative with additional benefits for forest owners. As a specialist for disturbed forest sites, the future importance of Black Cherry might increase under a changing climate, not only as an intermediate species in secondary succession, but also as a timber species comparable to other non-native tree species in Europe. • Black Cherry (Prunus serotina Ehrh.) has an either positive or negative influence on soil conditions and nutrient cycling depending on the forest site. • Integration into silvicultural practices is a cost- and labour-effective alternative to control measures. • Black Cherry is able to alter species composition and site conditions demanding its control in nature conservation areas. [ABSTRACT FROM AUTHOR]

• Rich litter (RL) admixture improves base saturation of oak stands on acidified soils. • A RL share higher than 30% basal area is needed for a significant effect. • Clay content amplifies the rich litter effect in these sandy soils. Many West-European forests are located on degraded and acidified soils. Soil acidification has resulted in hampered ecosystem functioning and lower delivery of ecosystem services. Forest management, particularly the choice of tree species, can accelerate or counteract soil acidification by the quality of litter input. The positive impact of so called 'rich litter' on the soil nutrient status and belowground ecosystem functioning has already been evidenced in common gardens. Here, we evaluate the effect of the rich litter species black cherry (Prunus serotina Ehrh.) in mixed forest stands dominated by pedunculate oak (Quercus robur L.). We study the effects using a replicated set-up of 10 established forest stands (age 30 to 90) in Belgium, the Netherlands and Germany along an edaphic gradient in sandy soils on Pleistocene aeolian deposits. We hypothesize that black cherry has a positive effect on the soil nutrient status and aim to answer the following research questions: (i) does admixture of black cherry increase soil pH and base saturation? (ii) what proportion of rich litter admixture is needed in a poor litter matrix to observe significant improvement of the soil nutrient status? and (iii) does the magnitude of the rich litter effect interact with initial soil properties? The results of this study indicate that admixture of black cherry enhances the forest floor turnover and enriches topsoil chemical conditions significantly. Thickness of the litter layer decreases from a mean of 7 cm under oak to a mean of 4.5 cm under cherry and correspondingly base saturation increases to a maximum of 25%, NO 3 − concentration to 26 mg/mg and organic matter content to 8%. However, large shares of rich litter admixture (>30% basal area) are needed to improve topsoil conditions. Moreover, we find that rich litter effects are more pronounced on sandy soils with higher fine particle (loam + clay) content. This suggests that the actual impact of restoration efforts in acidified forest soils is a product of the trinity "litter quality – litter share – site quality". [ABSTRACT FROM AUTHOR]