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Early Soils Plants Vascular
We have seen the earlier emergence of endomycorrhiza, but they probably play a more widespread role as the carboniferous period went on. "CO2 atmosphere declined to values close to those of today by the latter part of the Carboniferous (Franks et al 2014). One of the principal causes of falling atmospheric CO2 was the development of land plants and the rise of forest ecosystems (Morris et al., 2015). This enhanced two key drivers of the geochemical carbon cycle: weathering of calcium-magnesium silicates in rocks and carbon sequestration. The burial of vast amounts of organic carbon led to a rapid rise in atmospheric oxygen (Glasspool et al., 2015). Therefore, the transition to root colonization by endomycorrhizas (in earlier fossils, they colonized aerial axes) occurred during declining levels of atmospheric CO2 and increasing O2 levels that probably enhanced respiration in soils" (Strullu-Derrien et al 2018).
This endomycorrhizal growth would have produced more glomalisation and hence GRSPs, that would have helped develop primary soil aggregation, utilising the weathered sediments and organic matter and encouraged by enhanced soil respiration. Various mixtures of these led to early soils.
Primary
Primary
This, the Carboniferous' period, was the time of micro-aggregation, where structures were built that made soil. It would have involved the products of the breakdown of the mycorrhizal fungal exudate glomalin. You may read that early aggregation would have been due to roots holding soil particles together, and this would certainly have been part of it, but needs the main glue (cement) process. Can roots and glue explain how soil started and help stabilised the edge of the deltas, that led to enough soil being able to support larger trees. Is there enough glue in the GRSPs to do that or are there other forces at work?
See how aggregate properties promote Soil Structure
Secondary
Secondary
A later form of aggregation, generally called macro-aggregation, involves humic subtances as the glue, arising from the process of humification. While there would be isolated places where this could happen it did not become widespread for another 100my
It may be that "the accumulation of SOC (Soil organic carbon) in large and small macroaggregates and to the accumulation of GRSPs in microaggregates (<0.25 mm)" Xiao 2020, shows this would fit with microaggregates being primary and macroaggregates being secondary.
2. Microaggregates
2. Microaggregates
Microaggregates:
Size: Microaggregates are much smaller than macroaggregates, typically ranging from 0.01 mm to 0.25 mm in diameter.
Composition: Microaggregates are primarily composed of clay particles and organic matter.
Formation: They are formed through the binding action of various organic substances, particularly microbial byproducts like polysaccharides, glues, and fungal hyphae.
Stability: Microaggregates are less stable compared to macroaggregates and can be more easily broken apart by physical disturbances or changes in environmental conditions.
Function: Microaggregates contribute to soil structure and stability by forming bridges between individual soil particles, which helps to prevent soil compaction and erosion. They also play a role in nutrient retention and microbial habitat.
Size: Macroaggregates are larger soil aggregates, typically ranging from 0.25 mm to several millimeters in diameter.
Composition: Macroaggregates are primarily composed of sand, silt, clay, and organic matter.
Formation: They are formed through the binding action of various organic materials, such as plant roots, fungal hyphae, and microbial byproducts (glomalin, polysaccharides, proteins, etc.).
Stability: Macroaggregates tend to be more stable and resistant to disruption by water erosion or mechanical forces due to the strong binding agents that hold them together.
Function: They provide pore spaces within the soil, facilitating water infiltration, aeration, and root penetration. Macroaggregates also help to protect organic matter from decomposition by physically sheltering it within their structure.
GRSP everywhere
GRSP everywhere
"We found that GRSP was a ubiquitous substance in ecosystems with an average concentration of 2.48 ± 0.38 mg g−1. The lowest values were found in marine ecosystems (0.36 ± 0.25 mg g−1) and the highest values were found in tropical upland forest ecosystems (7.93 ± 1.77 mg g−1)"... The GRSPe content in mangrove soils was 3.34 ± 0.04 mg g−1, which was second only to the tropical upland forest." Wang et al 2021 GRSPs appear to play two roles in building soil structures - flocculation and particle aggregation. See my hypothesis - Glomalisation
GRSP & Aggregates
GRSP & Aggregates
Wang et al 2021 examined found Glomalin-related soil protein (GRSP) was a novel particle cementing agent, and that::
Protein constituent of GRSP was mainly responsible for high flocculation activity.
Charge neutralization and bridging were GRSP particle aggregation mechanisms.
GRSP contained rich Fe, and formed Fe-rich flocs with particulate matters.
GRSP’s floc properties provide new insights into coastal environment improvement.
"The GRSP fraction acts as a particle aggregation “superglue”, binding organic matter and clay particles to form water-stable aggregates (Lombardo et al., 2019, Singh et al., 2020) and can be used as a significant particle aggregation driver (Chen et al., 2019b, Liu et al., 2020).
Particle aggregation controls soil-borne biogeochemical processes, and plays a fundamental role in the transport and eventual fate of sediment, pollutants, and nutrients in aquatic environments (Bilotta and Brazier, 2008, Chern et al., 2007, Droppo, 2001).
Thus, the investigating GRSP fraction particle aggregation is promising for coastal environment improvement" and ideal to see what may have gone on 300mya.
Conditions
Conditions
The GRSP fraction can be leached or washed from soils into streams or become a foam constituent and deposited downstream in floodplains and rivers (Adame et al., 2012, Harner et al., 2004, Singh et al., 2017).
Highly anoxic conditions in aquatic environment prevent GRSP fraction degradation, enhancing long-term GRSP fraction accumulation (López-Merino et al., 2015).
"The GRSP fraction has the potential to be utilized as an alternative bioflocculant. The bioflocculation paradigm could provide a new framework for understanding formation of flocs or aggregates in ecosystems."
Flocculants
Flocculants
Flocculants are macromolecules with the ability to flocculate, ie to aggregate or coalesce into small lumps or loose clusters. that can rise or fall, suspended solids, cells, and solid colloid particles [Zhang et al 2012). Flocculants are widely used to separate out unwanted particles, for drinking water purification, wastewater treatment, activated sludge dehydration, downstream processing, and food fermentation (Zhang et al 2007). Flocculants are classified into three groups: synthetic organic flocculants such as polyethyleneimine and polyacrylamide by-products, inorganic flocculants, including aluminum sulphate and polyaluminum chloride, and natural flocculants (bioflocculants) such as chitosan sodium alginate (Gao et al 2006). Bioflocculation is defined as a process in which mediation of flocculants is achieved in the presence of microorganisms or biodegradable macromolecular flocculants released by microorganisms (Czemierska et al 2017).
Morphological properties of GRSP bioflocculation. (a) GRSP; (b) kaolin; (c) kaolin+CaCl2; (d) GRSP+kaolin+CaCl2.
Particles
Particles
"Particulate matter (PM) is an important component of intertidal habitats and aquatic systems, controlling coastal water chemistry and the vertical distribution and transport of material (Droppo, 2001 . Neto et al 2006) GRSP can be transported and deposited in coastal and marine environments through soil erosion, river foam, pore water, and tidal water (Adame et al 2012 Chern et al 2007 ). The flocculating activity experiments suggested that GRSP might be a particle aggregation formation driver in coastal water." Wang et al 2021
From the evidence of mangrove soil, its anoxic conditions maintaining GRSPs, and their properties in terms of flocculation and particle aggregation, it would seem quite possible that these are similar conditions that surrounded the deltas over 300mya. There is enough evidence to suggest this primary aggregation led to the first early structured soils. The GRSPs ability to be washed downstream and deposited in floodplains and rivers, adds to the likelihood that this is how the deltas gave way to forests with their roots (Xiao 2020) and glue to make new deeper soil during the Carboniferous period
Purple Phage
Purple Phage
Viruses would almost certainly have been involved in aggregates at this period, and ever more, particularly with the wetting of particles,. They are part of the process when dry soil becomes wet.
"Because of the heterogeneous physicochemical structure of soil, including different hydraulic connectivity, particle and aggregate sizes, and pore spaces, soil samples can be highly variable, even a few millimeters or minutes apart. Meanwhile, amplicon and metagenomic studies both indicate that soil microbiomes are among the most complex on Earth, with high richness and evenness, a diverse 'rare biosphere'. This makes the reconstruction of microbial and viral genomes from metagenomes less efficient in soil than in most other environments" (Roux & Emerson 2022). There is also "a substantial amount of ‘relic’ DNA" Carini et al 2016. More on viral identification Trubi et al 2020
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