Fig. 1
Simplified theoretical diagram of expected interactions in the pH range between 4 and 6 with the microbial community structure (full diagram available in Additional file 1). The direct effect of pH is expected to be the biggest driver of microbial community structure. In this study, the pH gradient was produced by liming application, thereby producing quantifiable co-variables (Ca and Mg). The indirect effects are the “spillover” effect of the pH in the other soil and plant variables. Indirect effect 1 is mainly related to the solubility of elements (Al, B, Fe, Mn, Cu, Zn, P) and the cation exchange capacity (CEC), while indirect effect 2 is related to these effects on plant growth and consequently on soil organic matter (SOM) and nutrient cycling (e.g., K and nitrate, NO3). Temperature and soil water content (WC) are considered in this diagram only for the survey day of greenhouse fluxes (as a proxy for microbial activity)