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That's basically, well, not true. When trees break down they contribute to soil organic matter. Approx 58% of SOM is carbon (SOC) making soil one of the largest

That's basically, well, not true. When trees break down they contribute to soil organic matter. Approx 58% of SOM is carbon (SOC) making soil one of the largest carbon sinks on the planet. See https://en.wikipedia.org/wiki/Soil_organic_matter https://en.wikipedia.org/wiki/Soil_organic_matter

deleted 7y ago
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triclops200 7y ago
Does soil continue to break down over time or does it permanently sequester into peat/coal/oil? As far as I knew, basically all of the tree's cellulose eventually gets released over time into CO_2 via biological activity.
pjkundert 7y ago
If soil continues to accumulate in a healthy form, as it did on the Great Plains over millennia of grazing by bison herds, then yes. Old growth forests often grow on rocky land, and have little long-term depth accumulation. Source: hiking old growth forests over decades, and being a farmer.
- hinkley 7y ago
  Literally survivor bias. The old growth forests that survived loggers were the ones they couldn’t get to for a profit. Those will be in or near geographic barriers like swamps or rocky terrain.
  - pjkundert 7y ago
    Hmmm? I've rarely hiked in harvested and replanted forests; these are boring. I did most of my hiking in central/northern BC and Alberta, Canada. These are some of the largest tracts of old-growth timber in the world. The many old-growth forests I've hiked (sample: >1,000km, mostly dominated by conifers), with last burn times ranging from decades to centuries, have rarely boasted deep soil levels. This hypothesis is supported by existing research: https://www.researchgate.net/publication/225314103_Soil_Carbon_Accumulation_in_Old-Growth_Forests https://www.researchgate.net/publication/225314103_Soil_Carb... Old-growth coniferous forests are great -- but they're not a big "carbon store". If you want land-use based carbon storage, I'd recommend investigating where the continent-wide, massive, deep, healthy carbon-rich store of topsoil and humous came from -- grazed grasslands and scrub brush.
    - hinkley 7y ago
      Oh, North Canada? That's some tricky terrain. Bedrock is very near the surface, and you're right, it's hard to build up. Short growing season, for one. The article you link mentions softwood forests being problematic for carbon accumulation. Not hardwood forests. Old growth temperate hardwood forests are quite rare now, and some of the apex tree species in those forests have very serious pathogens keeping them from re-establishing, more's the pity.
- drderidder 7y ago
  Lack of soil accumulation does not mean the soil evaporates into thin air; it is taken up by the watershed and redistributed downstream. The same carbon cycle is in effect; accumulation in any particular terrain has really nothing to do with it.
koheripbal 7y ago
There is an upper limit to the amount of CO2 that soil absorbs - it's clearly not infinite. There is an equilibrium in the Earth's natural Carbon cycle. Once a soil matures (a process that might take many decades), the amount of CO2 retained vs emitted reaches equilibrium.
- llebttam 7y ago
  Some thoughts on finite CO2-absorbing capacity: - If these forests are sustainably logged, we can take some of the carbon out and sequester it in buildings (or even just bury it), allowing the forest to regrow and absorb more carbon. - I have a theory that presently discussed global climate change solution only needs to buy us a maximum of 100 years, and by then our tech for dealing with silly problems like excess carbon will have almost surely advanced beyond recognition. Given rates of progress in chemistry, physics, and materials science over the last two centuries, this isn't crazy.

deleted 7y ago

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triclops200 7y ago

Does soil continue to break down over time or does it permanently sequester into peat/coal/oil? As far as I knew, basically all of the tree's cellulose eventually gets released over time into CO_2 via biological activity.

pjkundert 7y ago

If soil continues to accumulate in a healthy form, as it did on the Great Plains over millennia of grazing by bison herds, then yes. Old growth forests often grow on rocky land, and have little long-term depth accumulation. Source: hiking old growth forests over decades, and being a farmer.

hinkley 7y ago
Literally survivor bias. The old growth forests that survived loggers were the ones they couldn’t get to for a profit. Those will be in or near geographic barriers like swamps or rocky terrain.
- pjkundert 7y ago
  Hmmm? I've rarely hiked in harvested and replanted forests; these are boring. I did most of my hiking in central/northern BC and Alberta, Canada. These are some of the largest tracts of old-growth timber in the world. The many old-growth forests I've hiked (sample: >1,000km, mostly dominated by conifers), with last burn times ranging from decades to centuries, have rarely boasted deep soil levels. This hypothesis is supported by existing research: https://www.researchgate.net/publication/225314103_Soil_Carbon_Accumulation_in_Old-Growth_Forests https://www.researchgate.net/publication/225314103_Soil_Carb... Old-growth coniferous forests are great -- but they're not a big "carbon store". If you want land-use based carbon storage, I'd recommend investigating where the continent-wide, massive, deep, healthy carbon-rich store of topsoil and humous came from -- grazed grasslands and scrub brush.
  - hinkley 7y ago
    Oh, North Canada? That's some tricky terrain. Bedrock is very near the surface, and you're right, it's hard to build up. Short growing season, for one. The article you link mentions softwood forests being problematic for carbon accumulation. Not hardwood forests. Old growth temperate hardwood forests are quite rare now, and some of the apex tree species in those forests have very serious pathogens keeping them from re-establishing, more's the pity.
drderidder 7y ago
Lack of soil accumulation does not mean the soil evaporates into thin air; it is taken up by the watershed and redistributed downstream. The same carbon cycle is in effect; accumulation in any particular terrain has really nothing to do with it.

koheripbal 7y ago

There is an upper limit to the amount of CO2 that soil absorbs - it's clearly not infinite. There is an equilibrium in the Earth's natural Carbon cycle. Once a soil matures (a process that might take many decades), the amount of CO2 retained vs emitted reaches equilibrium.

llebttam 7y ago
Some thoughts on finite CO2-absorbing capacity: - If these forests are sustainably logged, we can take some of the carbon out and sequester it in buildings (or even just bury it), allowing the forest to regrow and absorb more carbon. - I have a theory that presently discussed global climate change solution only needs to buy us a maximum of 100 years, and by then our tech for dealing with silly problems like excess carbon will have almost surely advanced beyond recognition. Given rates of progress in chemistry, physics, and materials science over the last two centuries, this isn't crazy.