- What are the soil characteristics in the regions where the sampling campaign is conducted?
The soil in the region was formed after the last Ice Age and is relatively young, with an absolute age not exceeding 15000 years. The landscape in the sampling region is characterized by plains, and the elevation above sea level does not exceed 25 meters.
The region is characterized by peat, gley, and podzol soils, where inland dune relief was formed. Peat soils are classified as hydromorphic soils, formed under the prolonged influence of surface waters and shallow groundwater, where the capillary fringe of water reaches the soil surface (or was at the surface before drainage). In natural conditions, hydromorphic soils typically have a peat layer thicker than 30 cm.
In region-dominated histosol, muck and mucky peat are found in wetland land use, while moderately and well-decomposed wood, sedge, and sphagnum peat are present in mining, forest, semi-natural, and agronomy land use.
- What unique factors influence the composition and structure of the soil in each of these regions?
The development of soils in Latvia is primarily influenced by human economic activity
and climate in a boreonemoral zone where precipitation exceeds evaporation. Elevated moisture levels and anaerobic conditions promote the accumulation of poorly decomposed organic matter – peat.
The largest threat to the health of peat soils in this region is the drainage systems. Drainage aerates the peat soil, enriching it with oxygen. This process makes nutrients more available to plants, increasing primary productivity, but negatively affects the peat layer by exposing it to mineralization and compaction.
Drained peat is often poor in mineral elements, and historically, fertilizers (P and K elements) have been applied to improve growing conditions. Restoring the hydrological regime in formerly fertilized areas raises concerns about the leaching of mineral nutrients.
- Did you face any challenges related to the specific climatic or geographical conditions of each region? What challenges? How did you face these challenges?
In the boreal zone, the relatively short vegetation season and the delayed start of the summer season lead to a shift in the timing of soil sampling. In this region, soil moisture, vital for soil fauna, is optimal during spring and autumn. The slow warming of the soil after the cold season creates conditions where spring is not suitable for the development of soil organisms due to the low soil temperatures. At the same time, mid-summer is limited by relatively low soil moisture. As a result, the highest diversity of soil invertebrate fauna in the boreal region is observed in late summer (August) and early autumn, when most of the samples—earthworms, macrofauna, and mesofauna—were collected.
In the context of climate change, predicted natural extremes are already impacting soil sampling under current climate conditions. An unexpected storm in mid-summer unusually increased the water level for approximately two weeks and may have affected soil biological diversity.
- Have you discovered any unexpected peculiarities in a particular region’s soil structure or composition?
During sample collection, concerns previously confirmed in studies in this region were observed—that sometimes historical soil monitoring conducted several decades ago no longer reflects the current reality in nature.
Unfortunately, in some cases, soils recorded as histosols in the data did not correspond to this soil type according to international soil classification standards, as they did not meet the required 40 cm thick organic layer, for example, because of soil compaction.
- What specific soil particularities have you found that sparked your interest or were unexpected?
In semi-natural areas, the identification of intensities was based on management practices that significantly impact the health of organic soils—such as groundwater levels and forest harvesting methods. Initial samples suggest that the influencing factors need to be considered more broadly. This is because soil health is not always optimal in areas where the most appropriate management practices are applied based solely on these two factors.
- How did they affect the sampling campaign?
While these factors did not impact the sample collection, they could influence the interpretation and explanation of results.
- How does this soil sampling campaign differ from other soil sampling campaigns? Can you indicate the main difficulties you have found with a big soil sampling like this?
Unlike other soil sampling campaigns, this one involved collecting a significantly larger number of samples and analyses. When selecting the sampling areas, problems often arose with accessing the sites and transporting large samples to the transportation vehicles. This was due to the need to select the best and most appropriate site for each intensity. The project provided valuable experience in applying multiple soil sampling methods simultaneously and in planning the sampling process to ensure as uniform conditions as possible for the samples, thus yielding the most objective results.
- What impact do you anticipate the climate change experiments will have on soil and its biodiversity?
Since it has been observed in the boreal region that the diversity of mesofauna is highest during the season when soil temperatures and moisture levels are sufficient for invertebrate development, it can be predicted that a 50% reduction in precipitation as part of a climate change experiment will negatively impact overall biological diversity. In such less favorable conditions, there may be a dominance of cosmopolitan species, while more sensitive species might experience a decline in their numbers.
- What factors can increase the diversity of soil organisms? And which ones decrease it?
In the boreal region, the factor increasing biodiversity is the soil’s organic composition. Therefore, soils with higher organic matter should have higher diversity.
On the other hand, a high groundwater level positively affects the health of histosol soils but negatively impacts soil biological diversity. Excessive moisture in the soil creates an abiotic environment that reduces soil mineralization, which can be beneficial but is unfavorable for soil fauna. Therefore, higher soil biological diversity does not necessarily indicate better soil health across all land use types.
- What advice would you give to other researchers planning to conduct similar studies?
When doing something for the first time, allocating extra time for unforeseen activities is always necessary. One must be prepared for unexpected discoveries and consider the problem as broadly as possible so that in the future, it will be possible to explain previously unrecognized relationships as objectively as possible.
- Who ‘prepared the ground’ and made conditions ready for the soil sampling?
Our project partner from the Latvian State Forest Research Institute (LSFRI) Silava was in charge of the soil sampling campaign in the Boreal region.
