Soils are the largest organic carbon reservoir in terrestrial ecosystems, storing carbon as organic matter derived from decomposed plant, microbial, and animal residues that resist microbial decomposition. Recent research has revealed that organic molecules adsorbed onto soil mineral nanoparticles, such as iron and aluminum oxides, form the most stable and persistent pool of organic carbon in soils. However, the environmental factors driving the formation and destabilization of mineral-associated organic matter (MAOM) remain poorly understoodIn boreal and subarctic regions, climate change is causing trees and shrubs to encroach upon tundra ecosystems, leading to significant decreases in soil organic carbon stocks. While most studies have focused on the organic layers of soils—primarily composed of particulate plant residues—there is limited knowledge about how changes in vegetation types affect organic carbon stored in the mineral soil layers as MAOM.
Objectives
This project aims to understand how the progression of trees and shrubs affects MAOM processes in subarctic soils. To achieve this, we will utilize a natural ecotone from dwarf birch forest to tundra in the Swedish subarctic as our study site. By employing a new probe system, we will quantify MAOM formation and destabilization rates across this gradient. We will then compare these rates with various plant parameters (such as species composition, and tree density), soil parameters (including organic matter stocks, pH, moisture, and temperature), and microbial parameters (bacterial and fungal community diversity and composition). This project aims to identify the abiotic and biotic drivers influencing MAOM processes in subarctic mineral soils.
Methodology
- Analyze MAOM probes to determine stabilization and destabilization rates.
- Assess plant parameters to evaluate their influence on MAOM processes.
- Measure soil parameters to determine their effect on MAOM processes.
- Examine soil microbial parameters to understand their role in MAOM processes.
Skills and techniques acquired
- Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy.
- Stable isotope tracing using ¹³C and ¹⁵N isotopes.
- Soil organic matter fractionation techniques.
- Bacterial and fungal metabarcoding to determine soil microbial community composition.
- Advanced statistical analysis and data visualization.
Application process
- Flexible starting date,
- 45-60 cr
- Interested candidates should contact Dr. François Maillard at francois.maillard@biol.lu.se.