Greg, Concerning the core question in the article of "it did not drop below a minimum concentration of about 180 to 200 parts per million. Why?", there maybe another fungi related mechanism at work. Most forms of mycylium expire CO2. With a down turn in forest growth, due to low CO2 levels, a different type of fungi could have found additional nutrients in the forest floor from an increase in decaying biomass which, in turn, would have produced an increase in fungi generated CO2. The comment of *"The weathering rates by trees and fungi drop because low CO2 reduces plants' ability to perform photosynthesis, meaning less carbon-energy is supplied to the roots and their fungi. This, in turn, means there is less nutrient uptake from minerals in the soil, which slows down weathering rates over millions of years."* indicates that the investigators were looking at *mycorrhizal <http://agroforestry.net/overstory/overstory86.html> *fungi which is symbiotic to to tree growth/roots. *Saprotrophic fungi*<http://www.clarku.edu/faculty/dhibbett/tftol/content/3folder/saprotrophic.html>, however, are not symbiotic to tree roots and thrive on decaying matter. With a decrease in atmospheric CO2 levels coupled with the expected decrease in seasonal temperature ranges, there may have been an abundance of biomass decay within a cooler climate which is the most conducive type of temperature for the majority of saprotrophic species. The mycological world often shows a strong and complex regulatory effect upon the environment and some in the field believe the degree of complexity amounts to a basic form of intelligence or biological "internet'. The most striking example of this complexity is the slime mold species *Physarum polycephalum* <http://en.wikipedia.org/wiki/Physarum_polycephalum>: >From Wikipedia:
*"Physarum polycephalum* has been shown to exhibit intelligent characteristics similar to those seen in single-celled creatures and *eusocial* <http://en.wikipedia.org/wiki/Eusocial> insects. Maze-solving[*edit*<http://en.wikipedia.org/w/index.php?title=Physarum_polycephalum&action=edit§ion=5> ] A team of Japanese and Hungarian researchers claims that a specimen of *P. polycephalum* was able to navigate a maze made of *agar*<http://en.wikipedia.org/wiki/Agar>using the shortest route possible when two pieces of food were placed at two separate exits of the maze. *[1]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-NYT00-1> Event anticipation[*edit*<http://en.wikipedia.org/w/index.php?title=Physarum_polycephalum&action=edit§ion=6> ] By repeatedly making the test environment of a specimen of *P. polycephalum*cold and dry for 60-minute intervals, *Hokkaido University* <http://en.wikipedia.org/wiki/Hokkaido_University>biophysicists discovered that the slime mould appears to anticipate the pattern by reacting to the conditions when they did not repeat the conditions for the next interval. Upon repeating the conditions, it would react to expect the 60-minute intervals, as well as testing with 30- and 90-minute intervals.*[2]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-STNK08-2> *[3]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-Barone2009-3> Nutrient regulation[*edit*<http://en.wikipedia.org/w/index.php?title=Physarum_polycephalum&action=edit§ion=7> ] *P. polycephalum* have also been shown to dynamically re-allocate to apparently maintain constant levels of different nutrients simultaneously. *[4]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-DLBS10-4> *[5]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-Bonner10-5>In particular, specimen placed at the center of a *petri dish* <http://en.wikipedia.org/wiki/Petri_dish> spatially re-allocated over combinations of food sources that each had different *protein*<http://en.wikipedia.org/wiki/Protein> –*carbohydrate* <http://en.wikipedia.org/wiki/Carbohydrate> ratios. After 60 hours, the slime mould area over each food source was measured. For each specimen, the results were consistent with the hypothesis that the amoeba would balance total protein and carbohydrate intake to reach particular levels that were invariant to the actual ratios presented to the slime mould. Simulation of road networks[*edit*<http://en.wikipedia.org/w/index.php?title=Physarum_polycephalum&action=edit§ion=8> ] With more than two sources, the amoeba also produces efficient networks. *[6]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-NKNU04-6>In particular, the pattern connecting multiple food sources was shown to form efficient network structures like *cycles*<http://en.wikipedia.org/wiki/Cycle_(graph_theory)>and *Steiner minimum trees* <http://en.wikipedia.org/wiki/Steiner_minimum_tree>. In a 2010 paper, oatflakes were dispersed to represent *Tokyo*<http://en.wikipedia.org/wiki/Tokyo>and 36 surrounding towns. *[7]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-TTSIBFYKN10-7> *[8]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-Moseman2010-8> *P. polycephalum* created a network similar to the existing train system, and "with comparable efficiency, fault tolerance, and cost". Similar results have been shown based on road networks in the *United Kingdom*<http://en.wikipedia.org/wiki/United_Kingdom> *[9]* <http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-AJ10-9>and the *Iberian peninsula* <http://en.wikipedia.org/wiki/Iberian_peninsula> (i.e., *Spain*<http://en.wikipedia.org/wiki/Spain>and *Portugal* <http://en.wikipedia.org/wiki/Portugal>).*[10]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-AA11-10> Integration with electronics[*edit*<http://en.wikipedia.org/w/index.php?title=Physarum_polycephalum&action=edit§ion=9> ] The organism's reaction to its environment has also been used in a USB sensor*[11]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-Night07-11>and to control a robot. *[12]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-Night06-12> Computing[*edit*<http://en.wikipedia.org/w/index.php?title=Physarum_polycephalum&action=edit§ion=10> ] In a book*[13]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-Adamatzky2010book-13>and several preprints that have not been scientifically peer reviewed, *[14]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-Adamatzky2010-14> *[15]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-Adamatzky2008-15>it has been claimed that because plasmodia appear to react in a consistent way to stimuli, they are the "ideal substrate for future and emerging *bio-computing devices* <http://en.wikipedia.org/wiki/Biologically-inspired_computing>". *[15]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-Adamatzky2008-15>For example, - It has been reported that plasmodia can be made to form *logic gates*<http://en.wikipedia.org/wiki/Logic_gate> .*[14]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-Adamatzky2010-14>In particular, plasmodia placed at entrances to special geometrically shaped mazes would emerge at exits of the maze that were consistent with *truth tables* <http://en.wikipedia.org/wiki/Truth_table> for certain primitive logic connectives. However, in the *preprint*<http://en.wikipedia.org/wiki/Preprint>, when these primitive gates were connected to form higher logic functions, the plasmodium ceased to produce results consistent with the expected truth tables. Consequently, the composed gates were validated instead using a simulation speculated to model the streaming processes within a plasmodium. - An outline has been presented showing how it may be possible to precisely point, steer and cleave plasmodium using light and food sources. *[15]*<http://en.wikipedia.org/wiki/Physarum_polycephalum#cite_note-Adamatzky2008-15> End Wiki: So, the paleoclimate data, as it relates to fungi, would seem to require the incorporation of multidimensional possibilities. Two of the more interesting questions in this field are: Has the current population of slime mold species devolved from a more intelligent form? Or, can/will it's intelligence be increased? On your question of *"How might soil biochar addition change this equation?", *I've been looking into the issue of carbon uptake by mycorhizal fungi and have found the following paper to be the most instructive: *Carbon Uptake and the Metabolism and Transport of Lipids in an Arbuscular Mycorrhiza*<http://carbon%20uptake%20and%20the%20metabolism%20and%20transport%20of%20lipids%20in%20an%20arbuscular%20mycorrhiza/> *"Abstract* *Both the plant and the fungus benefit nutritionally in the arbuscular mycorrhizal symbiosis: The host plant enjoys enhanced mineral uptake and the fungus receives fixed carbon. In this exchange the uptake, metabolism, and translocation of carbon by the fungal partner are poorly understood. We therefore analyzed the fate of isotopically labeled substrates in an arbuscular mycorrhiza (in vitro cultures of Ri T-DNA-transformed carrot [Daucus carota] roots colonized by Glomus intraradices) using nuclear magnetic resonance spectroscopy. Labeling patterns observed in lipids and carbohydrates after substrates were supplied to the mycorrhizal roots or the extraradical mycelium indicated that: (a)13C-labeled glucose and fructose (but not mannitol or succinate) are effectively taken up by the fungus within the root and are metabolized to yield labeled carbohydrates and lipids; (b) the extraradical mycelium does not use exogenous sugars for catabolism, storage, or transfer to the host; (c) the fungus converts sugars taken up in the root compartment into lipids that are then translocated to the extraradical mycelium (there being little or no lipid synthesis in the external mycelium); and (d) hexose in fungal tissue undergoes substantially higher fluxes through an oxidative pentose phosphate pathway than does hexose in the host plant."* The primary question that biochar addition brings to mind is the possibility that the fungi would disassociate from the plant root as the biochar would be an easier carbon source. Thus, the plant would loose the mineral input from the fungi. Ron may help clarify this. On a side not: In reviewing this work, I'm drawn to the idea of the possibility of mycorrhiza fungi being modified to produce a harvestable form of lipids (oil). Best, Michael On Friday, January 24, 2014 11:26:44 AM UTC-8, Greg Rau wrote: > I haven't read the paper, but hopefully they sorted out the bio vs > abio effects of mineral weathering under high and low CO2. How might soil > biochar addition change this equation? Also I wouldn't expect this effect > in C4 plant communities whose CO2 uptake is decoupled from air CO2 > concentration. Paleosoil evidence of reduced (e.g. glacial period) > weathering? > Greg > > *Ancient forests stabilized Earth's CO2 and climate* > posted by news on january 23, 2014 - 3:31pm > > http://www.sciencecodex.com/ancient_forests_stabilized_earths_co2_and_climate-126645<http://www.google.com/url?q=http%3A%2F%2Fwww.sciencecodex.com%2Fancient_forests_stabilized_earths_co2_and_climate-126645&sa=D&sntz=1&usg=AFQjCNE8Zf136US18UPaGnoDwH-GX9ouxQ> > UK researchers have identified a biological mechanism that could explain > how the Earth's atmospheric carbon dioxide and climate were stabilised over > the past 24 million years. When CO2 levels became too low for plants to > grow properly, forests appear to have kept the climate in check by slowing > down the removal of carbon dioxide from the atmosphere. The results are now > published in Biogeosciences, an open access journal of the European > Geosciences Union (EGU). > > "As CO2 concentrations in the atmosphere fall, the Earth loses its > greenhouse effect, which can lead to glacial conditions," explains > lead-author Joe Quirk from the University of Sheffield. "Over the last 24 > million years, the geologic conditions were such that atmospheric CO2 could > have fallen to very low levels – but it did not drop below a minimum > concentration of about 180 to 200 parts per million. Why?" > > Before fossil fuels, natural processes kept atmospheric carbon dioxide > in check. Volcanic eruptions, for example, release CO2, while weathering on > the continents removes it from the atmosphere over millions of years. > Weathering is the breakdown of minerals within rocks and soils, many of > which include silicates. Silicate minerals weather in contact with carbonic > acid (rain and atmospheric CO2) in a process that removes carbon dioxide > from the atmosphere. Further, the products of these reactions are > transported to the oceans in rivers where they ultimately form carbonate > rocks like limestone that lock away carbon on the seafloor for millions of > years, preventing it from forming carbon dioxide in the atmosphere. > > Forests increase weathering rates because trees, and the fungi > associated with their roots, break down rocks and minerals in the soil to > get nutrients for growth. The Sheffield team found that when the > CO2concentration was low – at about 200 parts per million (ppm) – trees and > fungi were far less effective at breaking down silicate minerals, which > could have reduced the rate of CO2 removal from the atmosphere. > > "We recreated past environmental conditions by growing trees at low, > present-day and high levels of CO2in controlled-environment growth > chambers," says Quirk. "We used high-resolution digital imaging techniques > to map the surfaces of mineral grains and assess how they were broken down > and weathered by the fungi associated with the roots of the trees." > These are digital images of trenches in a mineral made by networks of > fungi. The circular feature in the picture on the right is a depression > made by the formation of a terminal spore by a mycorrhizal fungus, which > was linked to the roots of a maple tree under high CO2. Researcher Joe > Quirk says: "These spores are characteristic of the ancient type of fungus > that has associated with plant roots since plants first emerged onto the > land over 400 million years ago. This is why the image is so exciting > – it's good evidence this ancient fungus weathers minerals." > The width of the trenches is approximately 5 micrometers and the diameter > of the circular spore is about 55 micrometers (one micrometer is > one-thousandth of a millimeter). > (Photo Credit: Joe Quirk) > As reported in Biogeosciences, the researchers found that low atmospheric > CO2 acts as a 'carbon starvation' brake. When the concentration of carbon > dioxide falls from 1500 ppm to 200 ppm, weathering rates drop by a third, > diminishing the capacity of forests to remove CO2 from the atmosphere. > The weathering rates by trees and fungi drop because low CO2 reduces > plants' ability to perform photosynthesis, meaning less carbon-energy is > supplied to the roots and their fungi. This, in turn, means there is less > nutrient uptake from minerals in the soil, which slows down weathering > rates over millions of years. > "The last 24 million years saw significant mountain building in the Andes > and Himalayas, which increased the amount of silicate rocks and minerals on > the land that could be weathered over time. This increased weathering of > silicate rocks in certain parts of the world is likely to have caused > global CO2 levels to fall," Quirk explains. But the concentration of CO2 > never fell below 180-200 ppm because trees and fungi broke down minerals at > low rates at those concentrations of atmospheric carbon dioxide. > > "It is important that we understand the processes that affect and > regulate climates of the past and our study makes an important step forward > in understanding how Earth's complex plant life has regulated and modified > the climate we know on Earth today," concludes Quirk. > > Source: European Geosciences Union > > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/groups/opt_out.
