Tangled Webs: How Spatial Connectivity Governs Soil Biological Processes.

This presentation will explore how connectivity in soil systems affects biologically-mediated processes and hence the ability of soils to deliver the ecosystem goods and services on which sustainable environmental management depend.

Soils are characterised by a structural heterogeneity that is apparent across many orders of spatial magnitude. This is particularly the case in relation to the pore network, which is manifest as a hugely complex three-dimensional multi-scale labyrinth. It is the pore network that comprises the physical habitat for all soil organisms, representing a form of ‘inner space’ in which the entirety of belowground life inhabits and functions. The nature of the pore network – and particularly its connectivity – imparts a structural organisation to soil communities, and modulates the physical dynamics that occur between organisms and their resources, whether they are gases, solutes, particulates or prey. This has implications for soil organic matter dynamics, predator:prey interactions, population dynamics and even the basis for the remarkably high biodiversity found belowground. Interactions between water and the connectivity of the pore network also play a very significant role in governing such relationships.

Organisms carry a range of adaptations to enable effective growth and survival in such a complex architecture. For example, filamentous fungi are particularly well adapted to inhabiting porous media such as soils, by virtue of their growth-form based on extending and branching hyphae which form spatially-expansive connected networks called mycelia. These structures act as spatial integrators, connecting distal regions of the soil system with major consequences for nutrient cycling and plant growth.

Consideration of how connectivity plays such a fundamental role in governing soil function leads to concepts that effective soil management could be founded upon manipulating the extent of connection and disconnection in soil systems, across a range of spatial and temporal scales.