Networks on Networks (Second Edition)

'Networks on Networks' starts from the premise that the pore space in the Critical Zone is ideally suited for life because of its 3 phases, solid, water, and air, and because two of the phases are mobile, carrying nutrients and chemicals for signaling, allowing growth and the formation of connections between organisms. The connectivity properties of the pore space control the speeds at which all these related processes occur, generating the time scales for life, e.g., plant growth and soil formation. Our treatment of these properties, which are of such fundamental importance to life near the Earth's surface, is based on percolation theory over (physical) networks, the most accurate means of predicting the important flow and transport rates. It is through this lens that it is possible to identify some of the properties influenced by life, such as the increase in heterogeneity of the Critical Zone, which are important components of life's effect on making our planet a more suitable host for living objects. Other areas where the book's organization of understanding of hydrology and ecology overlap include finding a set of ecological optimality principles that allow prediction of plant species richness as a function of climate variables and the rate at which the biosphere sequesters carbon, which are both based on the prediction of the partitioning of rainfall at the Earth's surface into run-off and evapotranspiration.

The primary purpose of this book is to demonstrate the relevance of the network properties of the pore-space in the soil to the organization of understanding of plant growth, soil formation, river network development, and the water cycle, with the ability to directly relate time scales from seconds to the cycle of supercontinent break-up and assembly (Wilson Cycle). In the process, implications regarding the viability of the strong vs. the weak (Earth only acts like a living organism) Gaia hypotheses are addressed. All of this makes 'Networks on Networks' of great interest to those in the climate change community.