ABSTRACT
As soil scientists, have a healthy respect of the pervasive nature of soil structure in mediating all soil processes. However, until the complexity of structure-process interactions had led to a position of ignoring heterogeneity in favor of simpler homogenized systems, despite the recognition of the spatial-temporal variability in soil structure. The functional quantification of structural-microbial variation in soil is the ultimate goal. Water, oxygen, structure and substrate are all important factors regulating the magnitude and nature of microbial activity in soil. However, the relative importance of each is difficult to quantify due to their interrelatedness. The composition and heterogeneity of the physical framework of soil alongside associated moisture conditions act to channel microbial movement and mediate activity. For example, adhesion of bacteria to clay particles surrounding pore walls significantly influences plasmid transfer and survival rates. While structure may be the most important control over microbial processes it is not the only constraint on microbial activity.
