Biological soil covers: data on lichen, bryophyte and algae coverage in soils gathered by SoilSkin citizen science program using eBryoSoil app for smartphones

Biological soil covers (BSC) are small-sized topsoil communities composed mainly by lichens, bryophytes and algae that cover the terrestrial surface and play an essential role in maintaining the quality of the soil. However, little is known about their distribution, conservation, and ecosystem functions. The SoilSkin citizen science project aims to expand the scientific knowledge about the distribution of biological soil covers as an important step to evaluate the vulnerability of soil ecosystems of the Iberian Peninsula in the face of global change.

The project has a dedicated free of charge app for smartphones (eBryoSoil, available at Google Play https://play.google.com/store/apps/details?id=com.omarfiz.ebryosoil&hl=ca&gl=US) that is designed to obtain information about the coverage of the BSC communities. To use this app, users must select a sampling location and capture the three soil pictures required to complete a transect. These photographs are taken at a 27 cm distance from the soil, in a straight line with 15 meters of distance between each picture. After the acquisition of each image, users can quantify the coverage percentage of biological soil covers and select the type of habitat where the transect took place. The transect is complete when all three pictures and their respective information are uploaded.

The data presented here contains the records from SoilSkin participants, which mainly include a characterization of the cover patterns of biological soil covers, the type of habitat and the coordinates where each record was taken. The data set is composed by 279 unique records taken by 37 unique users from 28/11/2019 to 12/12/2020, across the Iberian Peninsula. These records specifically detail the percentage of cover occupied by three types of lichen growth forms (crustose, foliose and fruticose); liverworts; two types of moss growth forms (acrocarpous and pleurocarpous); algae; and soil. Moreover, each record also contains a description of the main type of habitat where the transect took place, that was selected from a list contained in the app with the following habitats:

• Dense forest - Habitat characterized by trees of more than 2 meters tall and canopy over 60%.
• Open forest – Habitat characterized by trees with more than 2 meters tall and a canopy below 60%.
• Shrubland – Habitat characterized by woody vegetation with less than 2 meters tall.
• Grassland – Habitat characterized by herbaceous plants.
• Agricultural land – Habitat characterized by temporary or woody crops.
• Coastal habitat – Habitat characterized by a landscape where land is in contact with the sea, creating a visibly different landscape from inner terrestrial one’s.
• Urban green spaces – Habitat characterized by a landscape in which man-made structures are present.

The database was revised to correct any possible mistakes (e.g., miscalculation of total percentages; habitat missing in some registers; removal of invalid registers).

The data file contains the following columns:

• Date: numerical variable indicating the “day”/”month”/”year” when the register was generated.
• User_ID:  categorical variable with the identification number of the user who gathered the record.
• Transect: categorical variable with the identification of the number of the transect.
• Photo_number: numeric variable that takes values of 1, 2 or 3 and corresponds with the identification of the photographs within each transect.
• Photo_label: character string with the identification of the photograph from each record.
• Register_localization: categorical variable with the identification of the geographic area where the record was done.
• Latitude: integer, variable indicating the latitude of the sampling location in decimal degrees.
• Longitude: integer, variable indicating the longitude of the sampling location in decimal degrees.
• Accuracy: integer, variable indicating the accuracy of the coordinates given by the GPS.
• Habitat_type: categorical variable with the description of the main type of habitat of the sampling location.
• Lichen_Crustose: integer, variable indicating the percentage of crustose lichen cover quantified in the record.
• Lichen_Foliose: integer, variable indicating the percentage of foliose lichen cover quantified in the record.
• Lichen_Fruticose: integer, variable indicating the percentage of fruticose lichen cover quantified in the record.
• Total_lichen: integer, variable indicating the sum of all lichen coverage quantified in the record.
• Liverwort: integer, variable indicating the percentage of liverwort cover quantified in the record.
• Moss_Acrocarpous: integer, variable indicating the percentage of acrocarpous moss cover quantified in the record.
• Moss_Pleurocarpous: integer, variable indicating the percentage of pleurocarpous moss cover quantified in the record.
• Total_ moss: integer, variable indicating the sum of all moss coverage quantified in the record.
• Algae: integer, variable indicating the percentage of algae cover quantified in the record.
• Soil: integer, variable indicating the percentage of soil visible in the record.