Soil temperature and moisture near downed trees and log barriers 5 years after a wildfire

Background: Forest recovery from natural disturbances is often linked to the biological legacies left in the aftermath. In the case of forest fires, coarse woody debris, and specifically downed logs, is recognized as preferential sites for forest regeneration, for the improved environmental conditions around them. In this study, we monitored the effect of barriers made of downed logs on near-surface (5 cm depth) soil temperature and soil moisture during the summer of 2022 (9 dates) in a conifer forest in Central Italy burnt in 2017. We took measurements at various distances from the barriers to assess the spatial extent of their influence on soil moisture and temperature. Leveraging the presence of log erosion barriers in the field, we compared the effects of naturally fallen (n = 14) and artificially placed (n = 19) logs. Results: We recorded lowest soil temperature and soil moisture in the immediate proximity of the logs, with values not significantly different from control points at a distance of one time the height of the barriers. This pattern was consistent throughout the summer, regardless of the type of barrier (natural/artificial). The decrease in soil temperature is probably caused by the interception of solar radiation, while the decrease in soil moisture is counterintuitive, and would require further investigation. The type of barrier did not influence soil temperature, but we recorded lower moisture around artificial barriers, suggesting that their positioning may have altered soil moisture retention capacity. Conclusions: From a management perspective, logs may be considered preferential sites for natural or artificial regeneration. Nonetheless their effect on near-surface soil moisture and temperature fades within a short distance, and their influence may be either positive or negative for natural regeneration, depending on the local limiting factors.