Pedology and CO2

In a previous post I provided an oblique link to a news release: Climate Change Alters Ocean Chemistry. It makes reference to conditions resonating with the theory of biorhexistacy:

The research team, which included Caldeira, Elizabeth M. Griffith and Adina Paytan of the University of California, Santa Cruz, plus two other colleagues, studied core samples of deep oceanic sediment recovered from the Pacific Ocean Basin. By analyzing the calcium isotopes in grains of the mineral barite in different layers, they determined that between 13 and 8 million years ago the ocean’s calcium levels shifted dramatically. The shift corresponds to the growth of the Antarctic ice sheets during the same time interval. Because of the huge volume of water that became locked up in the ice cap, sea level also dropped.

“The climate got colder, ice sheets expanded, sea level dropped, and the intensity, type, and extent of weathering on land changed,” explains Griffith.

“This caused changes in ocean circulation and in the amount and composition of what rivers delivered to the ocean,” adds Paytan. “This in turn impacted the biology and chemistry of the ocean.”

These folks are saying that momentous changes in oceanic chemistry recorded in the sediment record must have been predicated by equally momentous changes in soil chemistry, changes tied to both atmospheric carbon dioxide content and climatic conditions.

From a pedologist's view, it is clear that under the expanded humid, warm, stable conditions envisioned by H. Erhart for biostasis, we would see deeper residual soils and more rapid formation of argillic horizons. In terms of soil taxonomic orders (USDA), more intense chemical weathering would cause the expansion of inceptisols at the expense of mollisols, ultisols at the expense of alfisols, and oxisols at the expense of ultisols.

Caldeira and company tie warm climate to higher river calcium content, but strongly implicate higher atmospheric carbon dioxide as the primary driver of increased chemical weathering. Atmospheric carbon dioxide levels do not appear to be part of Erhart's construct, but could certainly enhance these pedogenetic trends.

Acid rain alarm bells are ringing faintly in the distance at this point. But it is a false alarm. Rain water pH is due mostly to equilibrium with atmospheric carbon dioxide. The carbonic acid formed buffers rain drop pH to 5.6, and higher atmospheric carbon dioxide increases the carbonic acid content, but it doesn't lower pH below 5.6. Other constituents accomplish that. Thus increased atmospheric carbon dioxide isn't being implicated in some futuristic acid rain scenario.

Oxisols, ultisols and spodosols would increase in extent with increased soil weathering. But could it also mean lower plant disease, and more nutritious crops? Increased carbonic acid would drive faster pedogenesis, as would increased the biological activity stimulated by higher carbon dioxide. For soil, that would mean a richer solute content in the soil water, more rapid formation of secondary minerals, more eluviation or translocation of minerals with percolation. To the list of pedological shifts at the soil order level, we can add the expansion of spodosols at the expense of inceptisols.

Something very positive can be expected for soil that is not captured in the shifting soil order paradigm. For plants and soil microbes, richer solute content would mean greater availability of mineral nutrients. In soil husbandry and slow food circles, higher mineral availability translates to healthier soil, lower plant disease, and more nutritious harvests. What the shifting soil order paradigm does signal is that soils will be at greater risk of losing their fertility to leaching. Having the soil chockablock full of biochar will be essential to mitigate this last effect. Let's start now.

(Recycled from nscss.org)