Forest as a nitrogen buffer (EVINBO)

Details

The forest area of Flanders consists mainly of forests that originated a few decades ago and that differ greatly from long-established forests in terms of function and biodiversity. These young forests often originated on fields or grasslands that were fertilised to a greater or lesser extent, while the soil of long-established forests (forest habitat) has not been fertilised or has been fertilised very little. Due to the high nutrient reserves and high pH of the soil in young forests, trees often grow faster there and, in the first few decades, fast-growing pioneer tree species can also be planted.

It is not well known to what extent young deciduous forests can store nutrients such as nitrogen and phosphorus and thus be an effective buffer against acidification and eutrophication of adjacent protected nature (Natura 2000 habitat) and still develop themselves into forest habitat under high nitrogen deposition. The differences in the ability of fast-growing deciduous tree species and slower-growing climax species to retain or utilise nutrients are also not yet sufficiently known. Slow-growing climax tree species such as oak are characteristic of forest habitat and are therefore often planted as target species, especially in public forests. Pioneer tree species such as cultivated poplar grow very quickly on nutrient-rich soil and are therefore often planted in private forests. With this project, we want to map the stocks of macronutrients and their change over time and space. We are looking at nitrate leaching because this outgoing flux has a negative impact on nearby protected nature. A better understanding of this can help to assess whether young forests are suitable as buffers for vulnerable nature, what is the best strategy to optimise this buffering effect, and how the biodiversity of forest habitat has the best chance of establishing itself in young forests that function as buffers for vulnerable protected nature.

Previous research focused on the filtering effect of coniferous forest versus deciduous forest on nitrogen deposition. This research showed that coniferous tree species maximise nitrogen capture and have a lower nitrogen requirement than deciduous tree species, which can lead to faster nitrogen saturation and nitrate leaching, with possible negative effects on adjacent habitats. In addition, conifers cause faster soil acidification and coniferous forests are less suitable for developing forest habitat biodiversity.

In this project, we focus on young deciduous forests that have developed on soil with elevated nutrient concentrations. Recent research shows that deciduous tree species can also immobilise nitrogen outside the growing season, similar to evergreen coniferous tree species. Moreover, young deciduous forests can not only have a buffering effect on vulnerable nature by capturing and sequestering nitrogen deposition, but may also provide important co-benefits such as carbon storage and the development of forest habitat biodiversity. For many species groups, little is known about young forests, but research indicates that biodiversity development in young forests is more likely if the young forest borders existing forest habitat, unless species are introduced.

Status	Running
Actual start/end date	01/01/2026 - 31/12/2029

Teams

• Forest Ecology and - Management

INBO Research theme(s)

• Forest