Geomorphic connectivity as a driver for the soil bioindicator distribution, implications for future research and modeling

Abstract

Hydrological structural connectivity, the degree to which water can move across a landscape, significantly influences water and sediment transport. While its impact on these processes is well-established, the extent of its influence on soil biological activity is still being researched. Changes in hydrological connectivity can affect soil water content, nutrient availability, and the distribution of soil organisms, ultimately impacting ecosystem functions. In this study a Mediterranean basin with a drainage area of 272 km² was considered for the interactions between geomorphic connectivity (CI) and the distribution of fungi to bacteria ratio (F:B) used as microorganism bioindicators. Results showed that the geomorphic connectivity ranges between -9.0 and +0.6. Therefore, using the F:B ratio, as weighting factor of structural connectivity (CI_FB), we observe an increase in connectivity between landform units, strengthening the relationships. The variable importance analyses showed a relationship between CI, F:B ratio and erodibility factor (K). CI_FB models was also capable of depicting geomorphic dis-connectivity in connection with a quiescent landslide and its impact on stream longitudinal connectivity, potentially leading to increase in-channel erosion downstream. These preliminary results can serve as a basis for constructing new working hypotheses regarding the structural-functional interactions on hillslopes, particularly when utilizing advanced geospatial data and analytical techniques. The tool, while requiring further development, holds significant promise for monitoring and conserving ecosystems, especially within watersheds. This is crucial for managing the impacts of climate change, not just in the Mediterranean region but also in other vulnerable areas.