Case study in the Arctic
The objective of this work package is to provide the long-term spatial patterns in soil biogeochemical properties across the tundra Arctic, the short-term response of the Critical Zone for soil respiration and carbon/nutrient fluxes, and the integration of these observations at the landscape scale.
5.1 - Field monitoring of permafrost soils during the late shoulder season
Collect long-term spatial patterns of vegetation structure, geomorphology, micro-topography, soil depth, soil structure and soil texture via the geophysical methods, and collect selected soil samples to add analysis of C quality and stability to the available data on soil carbon distribution, distribution of rock-derived nutrients, and parent material lithology available from the project WeThaw at UCLouvain.
5.2 - Soil hydrology characterization at a high space and time resolution
Proximal sensing observations at high spatial and temporal resolutions of soil moisture (droneborne GPR survey), land surface temperature (UAV-Thermal IR), frozen/unfrozen soil (on-ground GPR), and salinity (EMI) biweekly for 5 weeks (in June-July when the active layer is thickening). The surveys will be performed synchronously with ground-based measurements (Task 5.3) and sampling (Task 5.4).
5.3 - Soil water chemistry and associated redox conditions
Perform point measurements of soil moisture, soil temperature, and soil respiration along 5 positions in the toposequence and in 10 positions selected based on the electrical conductivity mapping (Task 5.1) to increase spatial coverage. One chamber will be used for continuous field measurements of Rs (continuous for 1 week at each position for 5 different locations along the toposequence), and sensors at the 15 positions will be used to obtain CO2 fluxes (biweekly for 5 weeks). Selected samples will be collected for the determination of CH4 fluxes. In addition, direct measurements of water table depth and active layer depth will be collected biweekly for 5 weeks.
5.4 - DOC and nutrient fluxes
Sample within 72h of the time-lapse survey (Task 5.2) soil pore waters for direct measurements of dissolved nutrients and DOC concentrations in solution at the positions of Task 5.3 (biweekly for 5 weeks). Measurements of soil water pH and redox potential will be performed. The stream draining the catchment will be sampled as an integrator of the response in dissolved nutrients and DOC concentrations combined with discharge punctual measures (biweekly for 5 weeks). Measurements of DOC biolability will be performed on selected water samples.
