- What are the soil characteristics in the regions where the sampling campaign is conducted?
The soils collected in Galicia (NW Spain), located in the Atlantic pedoclimatic region, include different types of uses and intensities. The study area is located in Toén (Ourense, NW Spain), which is known for its white wines (O Ribeiro) and landscapes.
Soil study selection was carried out considering different landscapes in similar climatic and geological conditions. In this sense, agricultural soils are vineyards located on regosols and a former forest area that has been converted into vineyards in the last 20 years. Two of the agricultural soils are located on the regosols, vineyards that have been cultivated for more than 100 years, with intensive use of pesticides and very low pesticide use (High and medium human pressure, respectively). The other agricultural study area is a former pine forest area converted into vineyards around 20 years ago. Since then, it’s been under agroecological management, where pesticides and chemical fertilizers have been reduced or eliminated (some fungicides are applied occasionally). In fact, in this area, the maximum vegetation record was recorded with up to 12 different plant species and 100% vegetation coberture in the LUCAS point area.
There is also a sand and stone quarry in the same area, where some technosols and leptosols were collected. Technosols are typical soils of mining and urban areas, characterized by the presence of mineral and organic parent materials of technogenic origin (agricultural or urban wastes, industrial by-products, building materials, transported natural materials). Usually, there are some problems with the establishment of vegetation cover due to lack of structure, big slope, low nutrients, or high contaminant levels.
In this sense, in the quarry area, soils were collected with remains of recent activities (most impacted area), and some quarries were accumulated. The medium intensity was an area partially restored with organic amendment some years ago and now with some pine afforestation, while the less impacted area is pine afforestation outside the quarry and without human influence.
Besides, this area presents a great problem of depopulation and population aging, so the semi-natural area was located in former cultivation areas in the 1970s decade. They were abandoned around 40 years ago and have since been partially naturalized with different types of forest formations: invasion of acacias (Acacia dealbata) (the area with the greatest degradation), Pinus pinaster afforestation and a typical Atlantic forest, mainly composed of Quercus robur (the least intense area). All of this is located on regosols. Nearby, wetland soils were collected, mostly gleysols, and with different intensities of management and human activity, from soils with herbicide application, only vegetation clearing or areas renaturalized by a riverine forest after 40 years of abandonment (previously, it was a pasture area).
Originally, the study was planned with the collection of all soils in the same catchment area and with similar geological and climatic conditions. Due to the fact that the study area has small population centers, the urban soils were collected in Ourense, the capital of the province (105,000 inhabitants), only 10 km away but in the same catchment area. The highest and medium impacted by human pressure are parklands within the university campus, with different heavy traffic intensities, pedestrian and pet-animals activities, and different management. Both soils are technosols, mainly composed of construction debris. The control area is located near a small river within the city on a river path and with occasional pedestrians.
- Did you face any challenges related to the specific climatic or geographical conditions of each region? What challenges? How did you face these challenges?
The study area has a Mediterranean climate (Csa) (Köppen classification) with cold, wet and partly cloudy winters. In our case, the previous months have been widely distributed rainfall throughout the winter and part of the spring, which slightly delayed the end of our sampling in the wetland area, which remained flooded until mid-June and where sampling was not possible until then. In fact, too much soil moisture due to high rainfall during winter and spring, even during some previous sampling days, gives us some issues in collecting soil structure due to excessive compaction.
Besides, due to the high slope in the quarry area, and in general, in all areas, this also represented an issue. For example, in several cases, it was not possible to arrive by car near the sampling sites, or, due to the high slope, a big sampling team was needed to be able to sample all areas within the expected time. In some cases, a small tractor was needed to carry out all the items for sampling and samples.
- Have you discovered any unexpected peculiarities in a particular region’s soil structure or composition? What specific soil particularities have you found that sparked your interest or were unexpected? How did they affect the sampling campaign?
In general, all study areas were previously studied to avoid potential unexpected particularities. However, our urban soil, which we thought was potentially less impacted by human activity, was filled with stones and debris some years ago, but its current state was nice and even seemed a natural area within the city. This was a potential problem, so the selection area needed to be updated in a short time.
On the other hand, we are quite interested in the collected soils since, in some cases with potential contamination and human activity, such as urban soils, we find an unexpected amount of macrofaunal biodiversity, mainly earthworms.
- How does this soil sampling campaign differ from other soil sampling campaigns? Can you indicate the main difficulties that you encountered during a big soil sampling like this?
This type of sampling was a small challenge at the organizational and management level. In our case, we usually collect soil or plant samples and occasionally some soil fauna samples, mainly earthworms or nematodes. In this case, it was necessary to collect a large number of samples (150) in a relatively short period (around a month) and at different sites. In addition, soil collection needed to be carried out with special measures to avoid possible plastic contamination of the sampling material. At the same time, mesofauna and macrofauna were also collected, the soil structure was collected with a special auge, and the soil was collected, sieved, and stored with special care samplings for the microbial analysis. All of these things are carried out in the field.
Likewise, the samples had to be processed in a short time, especially earthworms, microbial analysis, nematodes, and mesofauna, and in some cases, they needed to be shipped to other partners in special conditions and in a short time. Despite these challenges, this was possible thanks to a good team with extensive experience in other projects and with good coordination.
- What impact do you anticipate the climate change experiments will have on soil and its biodiversity? What factors can increase the diversity of soil organisms? And which ones decrease it?
Traditionally, human activities have placed pressure on soil health, mainly due to chemical, physical, or biological degradation. It’s expected that soil properties will be impacted and soil organisms, both richness and amount, will be decreased. Regarding climate change, it can act in different ways. In general, an increment in soil temperature, changes in soil moisture, and potential changes in soil are expected due to the erosion process by intense rainfalls (potential floods) or drought. This could have an impact on soil properties and biodiversity. It’s expected that these changes could impact soil organisms’ distribution or their activity because each organism usually has a temperature range for their biological activity that can be modified.
We are expecting long-term experiments to understand how climate change can impact different soil pressures since long-term experiments are usually scarce and sometimes with similar soil pressures.
- What advice would you give to other researchers planning to conduct similar studies?
This kind of study requires good planning and clear ideas from the beginning. Also, it needs an excellent organization, with a well-trained team in previous projects both for sampling and sample processing. In this sense, highly multidisciplinary teams with diverse knowledge are needed and capable of covering different types of analysis.
- Who ‘prepared the ground’ and made conditions ready for the soil sampling?
Our project partner from the University of Vigo was in charge of the soil sampling campaign in the Atlantic region.
