One of the ALFAwetlands project assignments is to study organic soils in wetland environments. Nine different wetland types across Europe, from restored peat extraction areas over wetland and riparian forests to coastal wetlands are being actively investigated. This broad range of environmental conditions require a unified approach to gather detailed information on greenhouse gas fluxes, changes in carbon stocks, relevant environmental factors, and specific methods for microbial and chemical analysis of soil samples.
Intensive studies may be challenging, both from technological and capacity perspectives: the annual soil carbon dioxide (CO2) balance is formed using summarized CO2 flux data over the year in monitoring and coherent data on mass-based Carbon (C) stock changes from above and below the ground (Fig. 1).
The diverse natural and local conditions need special attention during all stages – before (preparations, installations), during (measurements, sampling), and after the monitoring (evaluation). For instance, the C sequestration occurs in several dimensions horizontally and vertically, but also spatially and temporarily:
- extensive and diverse vegetation communities often go coherent with uneven spatial distribution (horizontal and spatial dimension)
- carbon is transferred from (living) biomass to dead organic matter in above-, below-ground and in-between (vertical dimension)
- physical and biochemical properties of organic soils and biological processes change over time, and depend strongly on external influences such as weather conditions or site management (if any), (temporal dimension)
- release of CO2 from soils by heterotrophic () process comes with recently deposited litter (“fresh”) and in soil made of previously accumulated dead organic matter (“old”). Thus, the CO2 (heterotrophic) needs to be treated separately from CO2, that is produced during autotrophic respiration (“plant respiration”).
Typically, the data used to calculate the soil carbon balance includes at least one year of monitoring; however, in the case of ALFAwetlands, two consequential years of periodic sampling are applied to gather a more precise picture: (I) determination of GHG (CO2, CH4, N2O) and environmental parameters such as soil temperature and soil water content, (II) the chemical analysis of soils, soil water, the (III) microbial analysis of soils, and (IV) the carbon content from above and below ground compartments such as defined litter fractions (if applicable) (Fig. 3)
To achieve one goal of calculating area-based emission factors, the complex experimental and site design structures require detailed installation, measuring, sampling and analyzing protocols for every single process step. Consequently, all partner institutions across Europe produce replicable and comparable results. Our harmonized methodologies represent a balancing best-fit approach for dozens of monitored sites in parallel, dedicated to all partners’ experience, respective allocated financial, technical and human resources for field work, laboratory analytics and final data collation and analysis. However, continuous technological developments enhance the periodic re-evaluation of our used state-of-the-art research methods to, for instance, increase the sampling frequency.