Exploring drivers of microbial drought sensitivity through combined laboratory and field approaches

Predicting how soil microbial communities respond to drought is a major challenge in terrestrial ecology, especially in heterogeneous landscapes where soils differ in texture, nutrient status, and climatic history. In this study, we combined a controlled laboratory incubation with a coordinated field drought experiment to explore whether background site characteristics and laboratory moisture–response curves can help anticipate ecosystem responses to reduced precipitation. We collected soils from six grassland sites across Italy spanning a broad gradient of pedoclimatic conditions and characterised their microbial and nutrient dynamics under varying levels of water availability.

In the laboratory, soils were incubated at five water-holding capacity (WHC) levels (10–80%) to establish moisture–response functions for a suite of microbial processes. We quantified microbial respiration, microbial biomass C, N and P, microbial growth via ¹⁸O-DNA incorporation, dissolved organic and inorganic nutrients (including dissolved P), and the activities of eight extracellular enzymes involved in C-, N- and P-cycling. These datasets provided site-specific profiles of microbial sensitivity and functional potential across a moisture gradient.

To assess whether these laboratory-derived patterns align with field drought behaviour, an in-situ rain-exclusion experiment was carried out in each grassland, imposing a 2.5-month drought during the plant growing season. The same microbial and nutrient variables were measured in the field following drought, enabling a comparison between controlled moisture–response curves and in situ functional responses.

Although data analysis is ongoing, preliminary results point to systematic links between background soil properties, laboratory moisture sensitivity, and field drought outcomes. Relationships appear to be process-dependent, suggesting that some microbial functions may be more predictable from laboratory assays and site characteristics than others. By integrating both laboratory and field manipulations, this work aims to develop a mechanistic and empirically grounded framework for assessing drought impacts on soil microbial communities.