Research Tobias Ceulemans

Abstract

Forests constitute a large and persistent carbon stock, which has increased over the past few decades. While the exact mechanisms remain unclear, it has been suggested that increased inorganic nitrogen input resulting from human activities has contributed to the observed increase in terrestrial carbon stocks. However, this nitrogen-induced carbon sequestration appears to vary widely across geographic locations, urging for a better understanding of its underlying mechanisms. Given the importance of microorganisms in both the carbon and nitrogen cycle, we expect that they play a central role in driving nitrogen-induced carbon sequestration. This project aims to investigate the role of microbial communities in driving nitrogen-induced carbon sequestration using a combination of a large-scale field study and a mesocosm experiment. We will collect litter and soil samples from temperate forests across a large nitrogen deposition gradient in Europe and use advanced molecular and laboratory methods to determine soil organic matter composition, fungal and bacterial communities and their functioning. To elucidate the distinct contributions of direct (increased nitrogen) and indirect effects (altered soil microbiome) of nitrogen deposition on soil functioning we will conduct a mesocosm experiment. Overall, our findings are expected to enhance our understanding of the role microbes play in coupling the carbon and nitrogen cycle and how global change is affecting forest carbon stocks.

Researcher(s)

• Promoter: Ceulemans Tobias
• Fellow: Boeraeve Margaux

Research team(s)

• Ecosphere

Project type(s)

• Research Project

Abstract

Insects are keystone species as they provide vital pollination services. Among the most cited drivers of insect decline worldwide are landscape homogenization, spread of introduced pathogens, use of pesticides, ongoing climate change and, most importantly, the loss of floral resources. Therefore, current environmental strategies to mitigate insect loss mainly advocate enhancing the floral resource abundance. However, whereas the primary focus now lays on increasing the quantity of food provisioning, maintaining sufficient food quality may be equally, or perhaps even more important for conservation. The quality of floral resources is primarily contingent upon the composition and relative abundance of nutrients such as nitrogen, phosphorus and base cations, sugars (mainly sucrose, fructose and glucose) and proteins and amino acids in both plant tissue and nectar and pollen. One of the primary environmental factors that can affect the nutritional quality of floral resources is plant nutrient availability, as it strongly affects plant physiological processes. However, nutrient pollution of natural and semi-natural ecosystems currently constitutes one of the most important components of global change worldwide, which is reflected by an approximate respective 100% and 400% increase of reactive nitrogen and phosphorus fluxes in global nutrient cycles. In an era of ever increasing nutrient pollution, this research proposal will focus on the specific contribution of different types of nitrogen pollution on the current biodiversity crisis. This research proposal is original in its focus on the link between nitrogen pollution and host plant quality, studying the underexplored hypothesis that degradation of plant resource quality may contribute to the widely observed insect decline. Further unique novelties include experimentally disentangling direct and indirect effects of nitrogen pollution and its common mitigation strategies in nature restoration and disentangling effects of pollution with reduced (mainly originating from agriculture) versus oxidized (mainly originating from combustion processes) nitrogen compounds via experiments and large-scale observational evidence across Europe (>25 000 standardized observations in >10 countries). We also aim to identify, for the first time, species-specific critical thresholds of pollution with oxidized and reduced nitrogen across taxonomic groups. This novel evidence may have far reaching ramifications for environmental policy regarding nitrogen that currently does not discriminate among reduced versus oxidized compounds for biodiversity conservation. To obtain these goals, we will use host plants and butterflies as model species as they have been proven to be very sensitive to environmental changes and relatively easy to use in experimental designs. The general objectives of this research proposal are to quantify the effects of nitrogen pollution on plant resource quality on the one hand, and to evaluate the subsequent effects on the behavior and fitness of phytophagous butterflies, on the other. Furthermore this proposal aims to disentangle the primary effects of nitrogen pollution from secondary, potentially confounding effects of nature restoration methods to mitigate nitrogen pollution. The general expectation is that the nutritional quality of plant resources is affected by nitrogen pollution and, in turn, negatively affects butterfly fitness and behavior. We also expect that current nitrogen pollution mitigation strategies also negatively affect butterflies, potentially compounding the general decline of insects. Finally, we expect that the experimentally determined relative contribution of both drivers will be reflected in large-scale observations of species decline and that these insights will lead to novel environmental policies and nature restoration strategies to mitigate biodiversity loss.

Researcher(s)

• Promoter: Ceulemans Tobias

Research team(s)

• Ecosphere

Project type(s)

• Research Project

Abstract

LIFE HARWIN is part of the LIFE sub-programme "Nature and Biodiversity". The project region suffers from several threats like habitat fragmentation and too small populations of key species. In this project we aim for the ecological restoration and quality improvement of 350 ha qualifying habitats along the entire gradient of the Winge Valley: aquatic habitats 3130 (annex species Luronium natans), 3140, 3150; heathland habitats 6230*, 4030, 4010; grassland habitats 6410, 6510; fen habitats 7140, 7230 and forest habitats 9120, 91E0*, 9160. Target locations for the restoration of habitats are consistently chosen adjacent to restore habitat connectivity and attain a favorable habitat size. This is crucial because remaining habitats are mostly small and isolated, characterized by a lot of species loss and not part of a sustainable natural ecosystem anymore. This restoration will also benefit the expansion or (re)colonization of several Annex I species of the Birds Directive and Annex II species of the Habitat Directive. For achieving this goal, Natuurpunt and ANB, two professional nature conservation managers and the main landowners of the project area will implement the restoration actions. This cooperation is reinforced by the academic input of APM and Antwerp University , both with experience within the project area, who will bring in their expertise in studying populations confronted with environmental pollution and habitat fragmentation and with restoration of remnant populations through ex-situ cultivation and reintroduction . The partnership thus ensures the valorization in practical applications of environmental science, in defiance of any gap that can exist between academic scientists and professionals and volunteers. Therefore, the expertise of the Dutch umbrella foundation LA, that was founded precisely to bridge the gap between academic institutions and professionals and volunteers, will be indispensable for the goals of this project.

Researcher(s)

• Promoter: Ceulemans Tobias

Research team(s)

• Ecosphere
• Geobiology

Project website

Project type(s)

• Research Project