Recovery of post-agricultural forest: tree species determines soil properties and possibilities for ecosystem restoration

Reforestation of agricultural land in many European countries has progressed more slowly than anticipated. Many years’ fertilization has caused an accumulation of nutrients in the top soil layer. Phosphorus (P) has proven to be particularly persistent and elevated concentrations in soil and vegetation are found up to thousands of years after agricultural abandonment. This persistently elevated bioavailable P is a paradox for ecosystem recovery in post-agricultural forests: on one hand, higher P bioavailability stimulates stand productivity and tree growth but, on the other hand, it limits the development of typical forest plant communities (Baeten et al. in press) and associated organisms. Limitation of bioavailable P seems to be a necessity for the recovery of species-rich target communities and for the conservation of endangered species (Wassen et al. 2005). Reforestation of agricultural land results in a decrease in soil pH with increasing forest age, but the extent and rate of soil acidification differs highly between tree species. Gymnosperm tree species are often contrasted to angiosperms because of their acidifying impact on soils. We will present data showing that rapid (within 2 decades) changes in soil properties can also occur beneath different broadleaved tree species. Ca concentra¬tions in leaf litter seem to be the driving factor for differences between species: tree species with higher litter Ca concentrations such as Populus and Fraxinus support a significantly higher soil pH, base saturation degree and lower quantities of bioavailable aluminum compared to the Ca-poor Fagus and Quercus species. Tilia and Prunus trees are intermediate between these ‘soil preservers’ and ‘soil acidifiers’. Furthermore, tree species have a major influence on the short-term and long-term bioavailability of P. Below ‘soil acidifiers’ we found significantly higher bioavailable and slowly cycling P fractions compared to ‘soil preservers’ which mainly retained P in less soluble pools. To date, there are no integrated studies on the long-term effect of different broadleaved tree species on soil properties in general and the bioavailability of P through soil acidification in particular. Most studies evaluating the bioavailability of P use extraction methods that only provide short-term dose-response insights into the readily available P pool for plants and soil microbes. However, for studying the role of P in recovering (semi)natural ecosystems, it is much more relevant to gain insight into time-scales extending a single growing season (Richter et al. 2006) and to include more slowly cycling P fractions. We discuss six common garden experiments in which broadleaved tree species have been planted on loamy agricultural soil for between 5 and 35 years. We argue that vegetation choice can be an important driver of regional biogeochemistry and biodiversity

Modellering van de impact van het vegetatietype (loofbos, naaldbos en heide) in infiltratiegebieden op de waterkwaliteit in het stroomgebied: deposities en uitspoeling van nutriënten onder bos en heide in het stroomgebied van de Zwarte Beek

B

Verzuring

B