Environmental conditions of dry stone walls’ wildlife

Juanola Gassiot, Martí
Dry stone walls are known to be notorious biodiversity promoters in anthropic areas. They are also believed to offer certain internal conditions that make them ideal habitats for small wildlife. This is a study framed in a larger project, known as PECT, with the aim of attempting to discover if these constructions present different inner conditions from the environment, and how they affect its inhabitants. It has been hypothesized that such thermal differences would act as a buffer, and, in turn, grant an optimal resting spot for ectotherm regulators. In order to prove it, field monitoring with external temperature recording devices was done for one month for every season. The study area was located between the two terms Llers and Avinyonet de Puigventós, from Catalunya, Spain. Inside this area, there were ten different study sites, where a section of dry stone wall was selected to host four different recording devices: on top of the wall, on the north face, on the south face, and on the ground in front of the south face. Once all the information was gathered, the obtained data was sorted and represented in different figures. This data was also used to create a simulated model for each position and each season on the body temperature evolution of an hypothetical lizard, with the help of the R package ‘NicheMap’. Finally, four optimal scenarios for every season through an average day were made. The outcome of each situation shifted in accordance with the external temperatures and the body temperature of the lizard. While in the winter scene the subject didn’t change at all, in the other three seasons it was clear how it searched for the best spot throughout different hours of the day. These results, combined with previous evidence, would point towards a beneficial factor found in dry stone walls’ microhabitats. Even if other decisive factors were not taken into account, the end goal of this work was accomplished, demonstrating how these walls' inner conditions can be a refuge for small wildlife ​
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