Research team

Expertise

Willem-Jan Emsens is eco-hydrologist, vegetation scientist, restoration ecologist and biogeochemist. He studies the relationships between vegetation, biogeochemistry and microbial communities, and aims to gain a better understanding of the functioning of biodiverse ecosystems. Key to his research is to investigate if and how we can restore heavily degraded ecosystems, with a focus on grasslands and wetlands. His PhD thesis dealt with the restoration of small sedge and brown moss communities in iron-rich peatlands. His line of research is based on the idea that one cannot fully comprehend the functioning of an ecosystem based on one scientific discipline, or solely by the study of one group of taxa. Therefore, his research is usually interdisciplinary, with a combined use of techniques from different fields of science (e.g. hydrochemistry, biogeochemistry, vegetation science, botany, microbiology, zoology, etc.). He is currently involved in several projects, amongst others a study on microbial communities in pristine, drained and rewetted peatlands across Europe (as part of BiodivERsa and FWO). Here, he investigates interactions between micriobial community composition, plant functional traits, nitrogen deposition and the emission of greenhouse gases (CO2 and CH4).

Ecosystem recovery after wildfire in Landschap de Liereman, Belgium 03/05/2023 - 01/03/2025

Abstract

A sudden wildfire in nature reserve "Landschap De Liereman," Belgium, burned down 30 hectares of wet heathlands and peatland. The affected area consists of highly threatened Natura 2000 habitats including dry and wet heathlands (4030 and 4010) and transition mires (7140). The fire destroyed most of the vegetation and soil fauna. A key question is whether (and if so, which) changes occurred in biotic and abiotic conditions, and whether these changes may hamper the recovery of the affected ecosystems and their endangered species. Moreover, it is unknown whether the wildfire led to dramatic changes in ecosystem functioning. In this study, we examine the multi-year effects of wildfire on soil biogeochemistry, vegetation communities, greenhouse gas emissions, mesofauna and soil microbial communities. Finally, we evaluate the ecosystem recovery process, and we provide feedback to the local site manager (Natuurpunt).

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  • Research Project

Grassland restoration by soil inoculation: interactions with environmental filters and priority effects. 01/04/2020 - 31/03/2021

Abstract

The majority of originally nutrient-poor grasslands in Western Europe has been eutrophied and degraded by human activities, which has resulted in a loss of associated biodiversity. The re-establishment of nutrient-poor conditions is the first step in grassland restoration, but despite abiotic recovery many restoration grasslands remain stuck in a seemingly stable and species-poor state. Emerging evidence suggests that not only edaphic filters but also dispersal limitation of plants and microbes -and their interactions- drive vegetation assembly. In this project, we use the framework of an existing large-scale and long-term field experiment to investigate if grassland restoration can be steered and accelerated by hay transfer and by inoculation of top soil collected in a mature and species-rich donor grassland. We combine state-of-the-art molecular techniques with methods from biogeochemistry and vegetation science to assess whether soil inoculation has a positive effect on vegetation assembly through the establishment of complex belowground plant-microbial correlation networks, and we investigate if the outcome of soil inoculation is dependent on edaphic properties of the grassland and on restoration treatments, including removal of the existing grass layer. Our interdisciplinary approach allows us to disentangle if, how, and through which mechanisms active manipulation of the soil microbiome affects ecosystem development.

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    • Research Project

    Development opportunities for Nardus grasslands on selected parcels in Landschap de Liereman. 13/03/2020 - 31/12/2020

    Abstract

    The central question in this study is whether the development of the microbial community in species-poor grasslands in nature reserve "de Liereman" can be controlled by the introduction of sod cut material collected in species-rich and well-developed reference grasslands ("soil inoculation"). We use state-of-the-art molecular techniques such as metabarcoding and qPCR.

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      • Research Project

      Greenhouse gas emissions from rewetted and eutrophied fens: from carbon sink to source? 01/10/2019 - 30/09/2022

      Abstract

      Fens are nutrient-poor wetlands characterized by active accumulation of organic plant matter (peat). This process requires waterlogged conditions and low microbial activity. Fens are important global sinks for atmospheric carbon dioxide (CO2), an important greenhouse gas (GHG). Unfortunately very few undisturbed fens remain, and most fens have been drained by human activity. Drainage triggers a myriad of cascading effects on fen biogeochemistry, vegetation and microbiology, and turns fens into sources of CO2. To make matters worse, fens are also increasingly threatened by nitrogen (N) enrichment. This may hamper peat formation, and could increase emissions of other potent GHGs such as methane (CH4) and nitrous oxide (N2O). The idea that degraded fens can quickly be restored by raising water levels seems naïve: recent observations suggest that rewetted fens often become nutrient-rich marshes. The effect of the drainage-rewetting cycle on GHG emissions is largely unknown, but might be dramatic. In this project, I will disentangle the interactive effects of fen hydrology and nitrogen enrichment on GHG emission. Moreover, I will investigate the influence of shifts in plant- and microbial community composition on altered GHG emissions. We hypothesize that drainage and N enrichment turn fens from sinks into sources of GHGs, and that this is partly due to shifts in plant- and microbial community composition. This change may be irreversible within human time-scales.

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      • Research Project

      Iron-mediated catastrophic shifts in peatlands: positive feedbacks and phytotoxicity. 01/10/2015 - 30/09/2017

      Abstract

      In this study, I aim to conduct fundamental research on a set of biogeochemical processes that, after rewetting, inhibit a shift from a drained (previously peat-accumulating) organic soil with net decomposition towards a soil with organic matter accumulation and nutrient retention. The emphasis will be on positive feedback loops on OM decomposition, with experiments to elucidate the effects of water table dynamics, iron chemistry and vegetation assembly.

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        • Research Project

        Iron-mediated catastrophic shifts in peatlands: positive feedbacks and phytotoxicity. 01/10/2013 - 30/09/2015

        Abstract

        In this study, I aim to conduct fundamental research on a set of biogeochemical processes that, after rewetting, inhibit a shift from a drained (previously peat-accumulating) organic soil with net decomposition towards a soil with organic matter accumulation and nutrient retention. The emphasis will be on positive feedback loops on OM decomposition, with experiments to elucidate the effects of water table dynamics, iron chemistry and vegetation assembly.

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          • Research Project

          Catastrophic shifts mediated by biogeochemical processes: feedback loops in organic soils. 01/10/2012 - 30/09/2013

          Abstract

          In this study, I aim to conduct fundamental research on a set of biogeochemical processes that, after rewetting, inhibit a shift from a drained (previously peat-accumulating) organic soil with net decomposition towards a soil with organic matter accumulation and nutrient retention. The emphasis will be on positive feedback loops on OM decomposition, with experiments to elucidate the effects of water table dynamics, iron chemistry and vegetation assembly.

          Researcher(s)

          Research team(s)

            Project type(s)

            • Research Project