Research Willem-Jan Emsens

Abstract

Anthropogenic soil acidification alters ecosystem functioning and triggers a decline in vegetation diversity, particularly in grasslands and heathlands. A solution for ecosystem recovery may be Enhanced Silicate (rock) Weathering (ESW), which was initially developed as a climate change mitigation technique. ESW consists of fine-grinding of silicate rocks, and then applying the powder to soils. During subsequent weathering, CO2 reacts with the mineral surfaces and is captured from the atmosphere, while HCO3- and base cations (e.g. K+) are released into the soil where they counter acidification. Although this procedure may remedy two urgent but also disparate problems, rising CO2 levels and biodiversity loss, effects of ESW have barely been explored in an ecosystem restoration context. The lack of holistic and long-term empirical data has resulted in an outlook of ESW that may be too optimistic, and potentially adverse effects of ESW have been disregarded. For example, we have no knowledge of how ESW and subsequent base cation regeneration affects community assembly of plants and microbes, nor do we understand how ESW interacts with soil organic matter (SOM) or with biotic actors, or how these interactions affect the ecosystem carbon (C) balance. In this project, we will fill in key knowledge gaps by combining three complementary approaches: (i) a synthesis of existing long-term field trials on ESW, (ii) a novel field experiment, and (iii) a full-factorial mesocosm experiment.

Researcher(s)

• Promoter: Emsens Willem-Jan

Research team(s)

• Ecosphere

Project type(s)

• Research Project

Abstract

"De Zegge" in Geel, the oldest nature reserve in Flanders, is a groundwater-fed peatland that harbours unique but highly threatened flora and fauna. The aim of this project is to map the current habitat quality through permanent quadrats ("PQs") in order to contribute to the conservation and restoration of the reserve. The project consists of vegetation, biogeochemical, hydrochemical and microbial surveys.

Researcher(s)

• Promoter: Emsens Willem-Jan

Research team(s)

• Ecosphere

Project type(s)

• Research Project

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).

Researcher(s)

• Promoter: Emsens Willem-Jan

Research team(s)

• Ecosphere
• Geobiology

Project type(s)

• Research Project

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.

Researcher(s)

• Promoter: Emsens Willem-Jan

Research team(s)

Project type(s)

• Research Project

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.

Researcher(s)

• Promoter: van Diggelen Ruurd
• Co-promoter: Emsens Willem-Jan
• Co-promoter: Verbruggen Erik

Research team(s)

Project type(s)

• Research Project

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.

Researcher(s)

• Promoter: van Diggelen Ruurd
• Co-promoter: Janssens Ivan
• Fellow: Emsens Willem-Jan

Research team(s)

• Geobiology

Project type(s)

• Research Project

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)

• Promoter: van Diggelen Ruurd
• Fellow: Emsens Willem-Jan

Research team(s)

Project type(s)

• Research Project

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)

• Promoter: van Diggelen Ruurd
• Fellow: Emsens Willem-Jan

Research team(s)

Project type(s)

• Research Project

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)

• Promoter: van Diggelen Ruurd
• Fellow: Emsens Willem-Jan

Research team(s)

Project type(s)

• Research Project