Insights from soil sampling in Germany's Eifel Region

What are the soil characteristics in the regions where the sampling campaign is conducted?

The sampling campaign is conducted in the Eifel region in North Rhine Westphalia, Germany. In the northern Eifel, clay-slate and greywacke are widespread. On slopes above the limestone, however, rendzinas, as shallow, mostly stony soils that dry out easily above the permeable ground, are often found. The typical brown soil is a loamy to sandy-loamy soil. The texture varies depending on the parent rock. The soils at the experimental sites are Cambisols (agricultural, semi-natural, and forest) with a weak horizon differentiation and Technosols (urban and mining), which are constructed and formed by human action.

What unique factors influence the composition and structure of the soil in each of these regions?

The soils in the Eifel region have developed due to many factors, such as stones, climate, plant and animal populations, and human activity.

The composition and structure of the soils in the experimental sites are mainly influenced by:

Agricultural: soil tillage, fertilization, soil compaction due to heavy machinery
Semi-natural: fertilization, soil compaction due to heavy machinery
Forest: tree felling and removal of wood with heavy machinery
Urban: compaction due to walking and leisure activities, entry of human materials (e.g., plastic), high emissions due to traffic activity on roads and railway lines nearby.
Mining: artificial backfilling and substrate layering during recultivation processes.

Did you face any challenges related to the specific climatic or geographical conditions of each region? What challenges? How did you face these challenges?

Some of the semi-natural sites are characterized by very stony and shallow soils, which made sampling difficult. Pushing the auger with the plastic liner to a depth of 30 cm was not always possible. Furthermore, the mixed samples contain more stones than the other land use types samples. Considering these adjustments, it was nevertheless possible to take all necessary samples.

With regard to the mining sites, the most recent recultivation site had a high proportion of sand and gravel in the topsoil. This material was relatively dry and still rather loosely layered, so it often fell out of the soil core samplers. Several attempts were often necessary to obtain the corresponding sample.

Have you discovered any unexpected peculiarities in a particular region’s soil structure or composition?

In areas with seminatural land use, the soil was extremely stony, even leading to one auger breaking during sampling. In regions affected by mining, the soil was notably loose and struggled to hold together in the soil core samplers.

How does this soil sampling campaign differ from other soil sampling campaigns? Can you indicate the main difficulties that you find on a big soil sampling like this?

First, we needed to identify sites with five totally different land use systems within one region. Then, securing the permissions also presented a challenge, as we had to convince owners/users/managers of the selected sites to allow sampling and sign the consent form. Additionally, there is a huge number of samples to be collected in a very tight time window with limited personnel. We also used new sampling methods and equipment that hadn’t been previously tested and sampled in land use systems where we had no prior experience.

Another challenge was the dense vegetation with shrubs and small trees in the forest and mining sites, which made movement and orientation difficult.

What factors can increase the diversity of soil organisms? And which ones decrease it?

Reducing management intensity can enhance soil organism diversity, whereas increasing it can reduce diversity.

What advice would you give to other researchers planning to conduct similar studies?

At the early stages of the project, it is important to draft a comprehensive and detailed protocol for sampling methods and procedures, similar to a handbook. Additionally, proper planning of these methods and procedures should be conducted in advance.

In general, it is advisable to get an idea of the conditions on the individual sites before starting the sampling campaign. This allows potential problems to be identified in advance and included in the planning. In this way, the size of the area and the time and personnel capacities can be optimally coordinated.