From the Centre for Ecology & Hydrology
Increased tropical forest growth could release carbon from the soil
A new study shows that as climate change enhances tree growth in tropical forests, the resulting increase in litterfall could stimulate soil micro-organisms leading to a release of stored soil carbon.
The research was led by scientists from the Centre for Ecology & Hydrology and the University of Cambridge, UK. The results are published online today (14 August 2011) in the scientific journal Nature Climate Change.
The researchers used results from a six-year experiment in a rainforest at the Smithsonian Tropical Research Institute in Panama, Central America, to study how increases in litterfall – dead plant material such as leaves, bark and twigs which fall to the ground – might affect carbon storage in the soil. Their results show that extra litterfall triggers an effect called ‘priming’ where fresh carbon from plant litter provides much-needed energy to micro-organisms, which then stimulates the decomposition of carbon stored in the soil.
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  IMAGE: Measuring CO2 efflux from the soil in subplots where the forest floor has been replaced with litter with a distinct isotopic signature. A wire mesh tent excludes forest litter from…
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Lead author Dr Emma Sayer from the UK’s Centre for Ecology & Hydrology said, “Most estimates of the carbon sequestration capacity of tropical forests are based on measurements of tree growth. Our study demonstrates that interactions between plants and soil can have a massive impact on carbon cycling. Models of climate change must take these feedbacks into account to predict future atmospheric carbon dioxide levels.”
The study concludes that a large proportion of the carbon sequestered by greater tree growth in tropical forests could be lost from the soil. The researchers estimate that a 30% increase in litterfall could release about 0.6 tonnes of carbon per hectare from lowland tropical forest soils each year. This amount of carbon is greater than estimates of the climate-induced increase in forest biomass carbon in Amazonia over recent decades. Given the vast land surface area covered by tropical forests and the large amount of carbon stored in the soil, this could affect the global carbon balance.
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 IMAGE: This is leaf litter around the buttress roots of a tropical tree at the study site in Panama.
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Tropical forests play an essential role in regulating the global carbon balance. Human activities have caused carbon dioxide levels to rise but it was thought that trees would respond to this by increasing their growth and taking up larger amounts of carbon. However, enhanced tree growth leads to more dead plant matter, especially leaf litter, returning to the forest floor and it is unclear what effect this has on the carbon cycle.
Dr Sayer added, “Soils are thought to be a long-term store for carbon but we have shown that these stores could be diminished if elevated carbon dioxide levels and nitrogen deposition boost plant growth.”
Co-author Dr Edmund Tanner, from the University of Cambridge, said, “This priming effect essentially means that older, relatively stable soil carbon is being replaced by fresh carbon from dead plant matter, which is easily decomposed. We still don’t know what consequences this will have for carbon cycling in the long term.”
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The people who pay for this study have no sense of value and no regard for those whose money they are spending.
I realize everybody is concentrating on the evil CO2 floating around in the world today, but in that great rush to vilify just one chemical component, did this study bother to study what else was released by decomposition and what those effects where?
I still think we should drink lots more coffee and consult the dregs about all this amazing litter for the truly definitive answer to it all-
http://www.telegraph.co.uk/sponsored/foodanddrink/6759611/Instant-coffee-more-environmentally-friendly.html
OR perhaps we should consult that Ozzie footy icon Guru Bob-
“If you fall off the donkey 7 times, you must bounce back up 8 times. BUT – if you fall off the donkey 10 times, you’re not cut out for riding donkeys…”
I for one think this study is extremely relevant and most of you are missing the importance.
Dr. Salby has proposed that temperature precedes CO2. He also, stated quite clearly that the major suppliers of CO2 are not the industrial regions but the tropical regions of the world.
He does not however explain the mechanism of this supply which I believe is given by this new study of Dr. Sayer. She provides the reason that more CO2 is released by natural forces and not anthropogenically.
Moana Loa may be recording this natural increase of CO2
It does not matter what we do or what nature does.
Everything wil lead to a higher CO2 concentration and that wil kill us.
As stated by Greenpeace, WWF and scienists thriving on funds suporting this dogma.
Harry
With the reduction in the use of paper because of online books, magazines and newspapers has anyone thought whether this may be a positive or negative feedback and is the carbon cycle capable of dealing with this?
Wel,
Let us clearcut Borneo, Sumatra, Papua New Guinea and the Amazone and all other regions I forgot (Afica perhaps).
Just to safe the planet and humankind.
Harry
Except for simply understanding trees and forests just for fun and curiosity, why worry in any way about whether forests take up or release CO2?
I maintain that any amount of forest and trees, the more the better, HAS to be a great thing. Therefore, leave them out of your worry list, leave them alone and let them thrive with all of the added CO2.
It is basically meaningless if more forest means more litter and more rotting. SO what?
If nature didn’t have a mechanism for keeping CO2 in some kind of equilibrium, then the world would have either become flooded with CO2 or depleted of CO2 long ago. The biosphere obviously has some kind of elastic response to changes in atmospheric CO2 as well as CO2 in soil and the ocean. It is not a coincidence that the composition of our atmosphere tends to remain relatively stable for long periods of geological time, then makes sudden shifts to new levels when something big changes. If the level of CO2 in the atmosphere has been relatively stable over the past couple thousand years, then all the sources and sinks must balance out. Since oceans are assumed to be the biggest sink, the other possible sinks, such as forests, must be small. There just aren’t that many sources for natural CO2. A forest fire doesn’t count as a source, because that’s just temperorary; it’s part of the cycle. A true source is something that adds CO2 to the cycle from outside of the cycle, such as a volcano or a petroleum seep. And a true sink is something that removes it from the cycle, such as formation of carbonate rocks and minerals at the ocean bottom. Forests are nearly neutral, or so close to neutral that it doesn’t matter. That’s just simple logic. Otherwise there wouldn’t be a stable atmosphere.
Funny how people get the wrong end of the stick. If you read the original article (or even just read the blog post properly), you see that nobody’s saying that extra growth is a bad thing – just that you can’t calculate carbon sequestration from trees alone. We can’t put all our faith into forests absorbing more carbon because things just aren’t that simple.
Sell your car, cycle to work, switch the lights off and lobby your local politician.
ReadThePaper says:
August 15, 2011 at 9:27 am
We can’t put all our faith into forests absorbing more carbon because things just aren’t that simple.
But, why would you need “faith” to begin with? Oh wait, I forgot, this is your anti-carbon religion. Sorry.
Sell your car, cycle to work, switch the lights off and lobby your local politician.
Greenie climate bedwetters first.
Doesn’t this all kinda make sense? The more a plant takes in CO2 the more the leaf litter will release? The solution may be as old as the native culture down in Central/South America. On year basis collect the litter from selected areas and burn it in Terra Preta (biochar) furnaces and generate electricity and use the results as a soil additive in farming areas. The original people of the area did that 1000’s of years ago.
Go Canucks says:
August 15, 2011 at 8:24 am
“I for one think this study is extremely relevant and most of you are missing the importance.
Dr. Salby has proposed that temperature precedes CO2. He also, stated quite clearly that the major suppliers of CO2 are not the industrial regions but the tropical regions of the world….”
You are right, Go Canucks, this paper should be seen as an interesting supplement to the forthcoming one of Dr. Salby.
Comparing the photographs. The (wom)manmade litter appears to be very different form the natural litter. There is green matter under the tent and the litter there seems to be short on leaves but long on drying/dried grasses. The worms in my garden would have a feast on the natural fallen leaves and run a mile from the artificial spread. I have never bothered to analyse the carbon content of the worm manure with which I have been feeding my plants and trees for decades but I know that the more leaves the more worms. And I believe that the little blighters themselves contain some carbon.
Incidentally my wife discovered last year that the areas of the garden on which she emptied our used coffee grinds had a significantly higher worm population than neighbouring areas. Can anyone suggest how this phenomenon has something to do with climate so that I might apply for a grant to further her research?
AGW is bi-winning!
Frankly in the area of climate science all papers could start with the opening line .
‘Its worse than we thought ‘ and no matter the rest of the contents it will match up to the desire conclusion.
The commentary says that “climate change” is accelerating tree growth. Not just nitpicking, it may in fact be that rising CO2 levels are directly accelerating the growth, not putative changes in the climate (eg warming or increased rainfall). As many at this blog have pointed out, CO2 is plant food.
The importance of the distinction is that even if we do not get the other benefits of a warmer climate from CO2 (longer growing seasons, fewer deaths from cold), we still will get the benefit of increased plant growth, ie more food for us and the rest of the ecosystem. Anthropogenic CO2 is a good thing.
“A new study shows that as climate change enhances tree growth in tropical forests…”
As soon as you clap eyes on the two words ‘climate change’, you know that you have stumbled upon yet more exciting news for the watermelon brigade.
When these eejits are proved wrong, which may be sooner, rather than later, their squeals of disbelief will echo around the world.
It will be only squeals, because it will be too darned cold to utter anything else.
I omitted to add that with a decreased global temperature, then the seven seas will eventually absorb more CO2, so there is no real concern. As is usual.
Stacey…
Paper? What the blazes are you wittering about girl?
Have you never been to a court of law, and seen the trolleys of paper rolled in?
When I was introduced to computers in the late seventies, there was an assumption that perhaps there could be less paper used on a world-wide basis.
Wrong – just tell me how many people own a computer that do not have a printer, and then carry out a little arithmetic.
Anyway, paper is not made solely from the fibre from trees.
“Given the vast land surface area covered by tropical forests and the large amount of carbon stored in the soil, this could affect the global carbon balance.”
“Could”, “might”, “it is thought”, “possibly”, “it is unclear”, …
How many more weasel words can you get into one article?
This article is not worth the paper (made from carbon-based vegetation) it is written upon.
Save the rain forests!
err…
umm…
Burn the rain forests!
err…
umm, that won’t work…umm…
Crispin in Waterloo is the only person so far to actually touch the matter at hand, which is that these idiots are looking at rain forests, wherein the soil is nutrition-poor due to the fact that the ecosystem is exceedingly robust, and naturally & rapidly withdraws any “dead” nutrients out of the soil up into the canopies. Carbon is a nutrient, QED, the biosystem isn’t likely to leave it to sink unused into oblivion the way it would in a subarctic bog.
It’s a pointless paper, unless this is the first time someone’s proved that higher temperatures don’t turn nutrient-efficient tropical rain forests into carbon-sequestering boreal taiga. On the other hand, since that’s so trivially obvious, this might actually be the first time somebody’s put that to pixels. Who knows?
From the PR
“The study concludes that a large proportion of the carbon sequestered by greater tree growth in tropical forests could be lost from the soil. The researchers estimate that a 30% increase in litterfall could release about 0.6 tonnes of carbon per hectare from lowland tropical forest soils each year. This amount of carbon is greater than estimates of the climate-induced increase in forest biomass carbon in Amazonia over recent decades.”
From the published work
“We predict that a future increase in litterfall of 30% with an increase in atmospheric CO2 concentrations of 150 ppm could release about 0.6 t C ha−1 yr−1 from the soil, partially offsetting predicted net gains in carbon storage. Thus, it is essential that plant–soil feedbacks are taken into account in predictions of the carbon sequestration potential of tropical forests.”
These two statements don’t appear to be entirely compatible.
The rest of the paper is paywalled so several questions remain unresolved. Is the estimation of 30% increase in litterfall based on anything empirical or is it just another WAG? Since the increase in CO2 ppm suggests an effect which will appear in the future, did they gather any baseline data for the present situation to be used to gauge any future changes? Given the great fecundity of tropical rainforest 0.6 ton/hec/yr doesn’t seem to be that significant a number. Do they provide solid data for past carbon uptake and the extent and trend of any increase attributable to increasing CO2? Is the supposed increase in CO2 release actually from carbon “sequestered” in the soil or just an increase in the annual cycle? In high latitude permafrost areas it is suggested that soil temperatures of 1-2 degrees C many feet below ground level are going to generate a cascade of methane releases. How is this compatible with the notion of large carbon sequestrations in tropical rain forests where the the soil temps are continually at much higher levels?
t
I’ve just been reading about how South American pre-Columbian Indians enriched the impoverished soils of Amazonia by creating terra preta, a nice friable soil which could sustain prolonged agriculture. Rather than practice ‘slash and burn’ agriculture, as was hypothesized by earlier anthropologists (but which turned out to be a post-Columbian introduction), they used ‘slash and char’: they carefully controlled the burning of organic material to create charcoal. Charcoal, when mixed into the soil along with organic detritus, stored and retained nutrients which ordinary Amazonian soils lost to the heavy rainfall. By adding to this terra preta by repeating this process over the years, patches of rich soils were created in the pre-Columbian era that sustain agriculture to this day. It seems to me that such practices would sequester enormous amounts of carbon dioxide if that were really needed.
For an interesting read on how most of North America’s pre-Columbian landscapes were heavily modified and managed by human beings going back thousands of years, as has been revealed with increasing explicitness by anthropologists and archaeologists in the last 30 years, I recommend Charles C. Mann’s 1491: New Revelations of the Americas Before Columbus. It’s a book that infuriates environmental extremists, as it completely dispels the myth of the pre-Columbian natural paradise with small tribes of Indians living in harmony with nature.