[Terrapreta] Prair(i)e is natures way of making terra preta.

[Brian Hans]

Hey TP ppl,
   
  My arnt you people prolific writers...it took me a while to hack thru it all.
   
  Firstly...As I mentioned, this is just some sort of hypothesis that one comes up with whilst burning stuff down...I dont know, maybe it was just the smoke...  I have no idea about the scientific lit search and was hoping by posting this hypothesis, some light could be shed on the topic. It seems the group knows very little detail on this topic which tells me that alot more can be done. But with that said...
   
  Certainly there is char being formed, if even .1%/ton fuel /a/y. I have not done a microscopic analysis to find it but y/y...it has to be there. And some prairies get burned y/y/y for 100's of years. Certainly if char is so long lived...there must be literally tons of it per acre  @ .1% fixing. Not knowing the exact's of what is going on (does anyone?) but when I burn a spot...there is blackness everywhere. Certainly some of that is in the form of TP sorts of structures. 
   
  Prairie is a fire dominate ecosystem. Without fire, prairie couldnt exist and trees (woody) would quickly take over succession. There are many different ways fire helps the prairie be a prairie; Seed exposure/scarification, soil warmth b/c of black soil surface, Duff removal, ... but mostly its because a prairie is simply like an iceburg, whereas most of its biomass is under soil level and its like cutting your hair to get a new hairdoo but the hair folicles are still there. Its this 'iceburg' aspect of grassland ecosystems that offers the ability for fire to clean up the dandriff of last years crop. As us prairie botanists say 'the suface is solar panels and sex organs...its down under where all the action lies'. 
   
  By the way...this concept is important when we talk about soils. A forest ecosystem has very little down under going on. Only ~6" has the real goodies and the rest of the soil is carbon/biota poor. A prairie ecosystem is reversed in this respect. When we talk about carbon sinks, forest floors should not be included, its the above ground that is the real sink. Prairies are the exact opposite in carbon sink-age. IMO, this concept offers important implications to the whole sequestering of C and ofc, we all know that TP is smackdab in the middle of that whole debate. Which is one of the reasons I have been musing this hypothesis. 
   
  Glacial till only provides the matrix for soils, its the biota that turns them into luscious prairie soils 6ft deep. 
   
  By the way, Im talking about the eastern tallgrass prairies, not the western dryland prairies. Western drylands had fires but considerably less frequently.
   
  I agree with Tom...where is the data?
   
  Peace, Brian
   
   
   
  Tom says;
  Where is the data? 

Before you jump to too many conclusions someone should do a full literature
search on this topic. I found several references on biochar and prairie
fires when I was doing an internet search a few months ago. I do not have
access to some key academic databases in soil science but I found that there
has been work on prairie fires and the role of the resulting carbon in soil
fertility.  If I remember correctly they concluded that fire stimulated
growth in grasses partly due to thermal shock, partly due to the elimination
of residues and competing grasses, partly due to nutrients in the burned
residue,  and only secondarily due to carbon accumulation. It was calculated
that he amount of carbon from burning contributed little to soil organic
carbon and long term accumulation. The concentration of inorganic elements
that results from burning stimulated growth for the first year but the
effects were not lasting. Similar studies have been done for rice straw. 

We saw these effects in the 1970s when we burned hundreds of acres using
field burning machines that we designed. We used to burn the residues from
our grass seed harvest In our Willamette Valley. Annual burning of more than
300,000 acres resulted in production of high purity seed and elimination of
volunteer plants and diseases. We designed and tested machines to control
combustion of the residue. We machine burned hundreds of acres on many
different grasses. Fossil fuel was only used to run the tractor and a fan on
the machine, The residue sustained it's own fire. Burnout was good. Char
left on the ground was not measured but it was probably more than open
burning because we released less to the atmosphere. Emissions were very
good. Most of the nutrients returned to the soil rather than put into the
atmosphere. Political pressure changed the regulations and reduced  burning
to less than 10% of the total acreage. It is used sparingly now for select
fields. In some areas more straw is returned to the soil which has improved
tilth and water use. Seed varieties have also changed with the market so we
now grow less annual and more perennial grasses. 

Tom Miles


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