Redwood Reader

Several articles this week bring us closer to the edge of our concerns about soil carbon in forest settings. We applaud the new work even as we see its blind spots. The first article is a summary of two studies done in England and Wales over twenty-five years in three thousand test plots monitored for that legnth of time. The studies measurted soil carbon in the first 15mm (6 inches) of soil, and found a steady loss over time. They attribute this to quickening pace of decay due to global warming, and that land user had little effect on the rate of of carbon loss.
New Scientist reported recently three quarters of published science is wrong. We often see results from research started before more information comes to light. Here is a fine example. This study started nearly twenty years before glomalin wass discovered. Since we believe starving glomalin can lie decaying at much greaster depths than this, we can even surmise why the ground appears to be sinking. I suggest first a history of previous land use for say fifty years, to be sure deeply deposited glomalin has all decayed. We would measure to a greater depth than 6 inches, as that is for row crop farmers and does not give a clear picture of soil carbon profiles in areas previously occupied by deeper rooted plants and trees. Lastly, measuring the top layer does not account for carbon being deposited at any greateerr depth. If your crop deposits glomalin to ten inches, and is replaced six inches every year, you will maintain fertility in the topsoil even as deeper deposits from previous land use decay. Like the U. S. FACE experiments, we would like to see this science repeated in forestlands to a much greaster depth, and with a historical land use analysis to know how much glomalin may be present at the site before measurements begin. It is also interesting to wonder about the surface water capacity of the sites and if that has changed over time. Ground radar may give a quick reading but a connection between water and glomalin needs to be quantified, preferrably as part of a wider study. We point out in response to the Guardian that richer soils often have less need for forasging mycorhizzia, and thus we expect lower production than in poorer soils.
“Warmer soils will have encouraged greater microbial activity so more rapid decay of organic matter in the soil, leading to greater discharges of gases.” Some of these are the very microbes fixing glomalin in the soil, a higher rate of activity will mean higher rates of carbon fixation. We will also find glomalin to greater depth annually of lands being reforested or rewilded. While the British scientists are worried their study shows little hope for controlling carbon dioxide, they contribute directly to our understanding, and pave the way for more focused studies based on a knowledge of glomalin. Three-quarters of the planet's soil carbon is trapped in the temperate zones, they note. Professor Kirk said: "It had been reckoned that the CO2 fertilisation effect was somehow offsetting about 25% of the direct human induced carbon dioxide emissions. It was reckoned that the soil temperature emission effect would catch up in maybe 10 to 50 years' time. We are showing that it seems to be happening rather faster than that."
In answer to that, we include CO2 Sciences article showing accelerated productivity over fifty years in the Amazon Basin, where carbon capture seems to be working better than expected. It is interesting how much we seem to depend on tropical forests for this when the soil isn’t very deep and the glomalin seems to turn over at an accelerated pace. If this is occurring at that rate, and temperate forests are not as quick to decay glomalin because they are cooler, then we can believe that three quarters of the earths soil carbon is in temperate zones. The problem is that it is clear no one is measuring carbon deposition and storage at tree root depths, water carrying capacity and the changes in soil as glomalin decays.
Finally, in reading archeological articles from Britain there is a lot of remorse over the use of tractors and bulldozers on the landscape after WWII. Several books have mentioned that WWII aerial photos revealed old depressions in the ground that often signaled ancient sites, even in areas farmed for hundreds of years. It all disappears under modern equipment, illustrating the extent of carnage on the ground due to those machines. Once again, we have no idea what we may have lost.

Nature
Editor's Summary
8 September 2005
Grounds for concern
http://www.nature.com/nature/journal/v437/n7056/edsumm/e050908-11.htmlThe possibility of a positive feedback between CO2 release from soils and global warming is one of the most contentious issues in climate research. The concern is that rising temperatures may be causing some of the massive reserves of carbon stored in the soil to be released into the atmosphere as the greenhouse gas CO2, resulting in a further increase in temperature and yet more CO2 release. So far what evidence there is for this feedback mechanism has come from small-scale laboratory and field experiments and mathematical modelling. Now a team from the UK National Soil Resources Institute and Rothamsted Research presents data from a long-term national-scale soil monitoring scheme that reveal extensive carbon losses during the past 25 years: land use has little effect on the rate of carbon loss suggesting a possible link to climate change.
News and Views: Environmental science: Carbon unlocked from soils
Changes in climate and land use are implicated as the main factors in the large-scale loss of carbon from soils in England and Wales over the past 25 years. The same picture is likely to apply much more broadly.
E. Detlef Schulze and Annette Freibauer
doi: 10.1038/437205a
Full Text | PDF (222K)
Letter: Carbon losses from all soils across England and Wales 1978−2003
Pat H. Bellamy, Peter J. Loveland, R. Ian Bradley, R. Murray Lark and Guy J. D. Kirk
doi: 10.1038/nature04038

Loss of soil carbon 'will speed global warming' http://www.guardian.co.uk/climatechange/story/0,12374,1565049,00.htmlTim Radford, science editor
Thursday September 8, 2005
The Guardian
England's soils have been losing carbon at the rate of four million tonnes a year for the past 25 years - losses which will accelerate global warming and which have already offset all the cuts in Britain's industrial carbon emissions between 1990 and 2002, scientists warn today.
The research dashes hopes that more carbon dioxide emissions might mean more vegetation growth and therefore more carbon removed from the atmosphere.
The unexpected loss of carbon from the soils - consistently, everywhere in England and Wales and therefore probably everywhere in the temperate world - means more carbon dioxide in the atmosphere, which means even more global warming, and yet more carbon lost from the soil.
"All the consequences of global warming will occur more rapidly. That's the scary thing: the amount of time we have got to do something about it is smaller than we thought," Guy Kirk, of Cranfield University, told the British Association Festival of Science, in Dublin.
He and colleagues sampled the top 15cm (6in) of soil at almost 6,000 fixed points in England and Wales between 1978 and 2003, to measure the changes in living and decaying matter locked in pastures, croplands, forests, bogs, scrubland and heaths.
Their findings, published in Nature today, show that carbon was being lost from the soil at an average of 0.6% a year: the richer the soils, the higher the rate of loss. When the figures were extrapolated to include all of the UK, the annual loss was 13m tonnes.
There was no single factor other than global warming that could explain such changes in non-agricultural soils, they said. "These losses completely offset the past technological achievements in reducing carbon dioxide emissions, putting the UK's success in reducing greenhouse gas emissions in a different light," said Detlef Schulze and Annette Freibauer, of the Max Planck Institute, in Nature.
In the past 25 years the average temperature has increased by half a degree centigrade and the growing season of the northern hemisphere has been extended by almost 11 days. Warmer soils will have encouraged greater microbial activity so more rapid decay of organic matter in the soil, leading to greater discharges of gases.
For more than two decades, climate scientists have tried to calculate the planet's annual carbon flow. Some of the carbon is absorbed by the oceans, to be trapped as limestone; some is locked in soil as peat or stored in woodland. The latest research implies that in a warmer world much of this "lost" carbon will find its way back into the atmosphere more quickly.
The study confirms the value of long-term research: the national soil inventory was established in 1978 as a network of fixed points at intervals of three miles, and the scientists used went on using the same techniques to measure the changes in soil carbon over more than 20 years.
Three-quarters of the planet's soil carbon is trapped in the temperate zones, they note. Professor Kirk said: "It had been reckoned that the CO2 fertilisation effect was somehow offsetting about 25% of the direct human induced carbon dioxide emissions. It was reckoned that the soil temperature emission effect would catch up in maybe 10 to 50 years' time. We are showing that it seems to be happening rather faster than that."

Continued Accelerated Growth of Amazonian Forests CO2 Science Magazine Volume 8, Number 36: 7 September 2005
For most of the past century it was believed that old-growth forests, such as those of Amazonia, should be close to dynamic equilibrium. Just the opposite, however, has been repeatedly observed over the past two decades. In one of the first studies to illuminate this new reality, Phillips and Gentry (1994) analyzed the turnover rates - which are close correlates of net productivity (Weaver and Murphy, 1990) - of forty tropical forests from all around the world. They found that the growth rates of these already highly productive forests had been rising ever higher since at least 1960, and that they had experienced an apparent acceleration in growth rate sometime after 1980. Commenting on these findings, Pimm and Sugden (1994) reported that the consistency and simultaneity of the forest growth trends that Phillips and Gentry had documented on several continents led them to conclude that "enhanced productivity induced by increased CO2 is the most plausible candidate for the cause of the increased turnover."A few years later, Phillips et al. (1998) analyzed forest growth rate data for the period 1958 to 1996 for several hundred plots of mature tropical trees scattered around the world, finding that tropical forest biomass, as a whole, increased substantially over the period of record. In fact, the increase in the Neotropics was equivalent to approximately 40% of the missing terrestrial carbon sink of the entire globe. Consequently, they concluded that tropical forests "may be helping to buffer the rate of increase in atmospheric CO2, thereby reducing the impacts of global climate change." And, again, they identified the aerial fertilization effect of the ongoing rise in the air's CO2 content as one of the primary factors likely to be responsible for this phenomenon.More recently, Laurance et al. (2004a) reported accelerated growth in the 1990s relative to the 1980s for the large majority (87%) of tree genera in 18 one-hectare plots spanning an area of about 300 km2 in central Amazonia, while Laurance et al. (2004b) observed similarly accelerated tree community dynamics in the 1990s relative to the 1980s. And once again, it was suggested, in the words of Laurance et al. (2005), that these "pervasive changes in central Amazonian tree communities were most likely caused by global- or regional-scale drivers, such as increasing atmospheric CO2 concentrations (Laurance et al., 2004a,b)."Expanding upon this theme, Laurance et al. (2005) say they "interpreted these changes as being consistent with an ecological 'signature' expected from increasing forest productivity (cf., Phillips and Gentry, 1994; Lewis et al. 2004a,b; Phillips et al., 2004)." They note, however, that they have been challenged in this conclusion by Nelson (2005), and they thus go on to consider his arguments in some detail, methodically dismantling them one by one.At the end of the day, it thus appears that a large body of scientists (see the references cited below) agrees that a wealth of scientific data confirms the reality of the ever-increasing productivity of earth's tropical forests, especially those of Amazonia; and they tend to agree that the concomitant rise in the air's CO2 content has had much to do with this phenomenon. We also agree, noting that an even greater wealth of laboratory and field data demonstrates that rising forest productivity is exactly what one would expect to observe in response to the stimulus provided by the ongoing rise in the atmosphere's CO2 concentration (see many of the Headings listed under Trees in our Subject Index).Sherwood, Keith and Craig IdsoReferencesLaurance, W.F., Nascimento, H.E.M., Laurance, S.G., Condit, R., D'Angelo, S. and Andrade, A. 2004b. Inferred longevity of Amazonian rainforest trees based on a long-term demographic study. Forest Ecology and Management 190: 131-143. Laurance, W.F., Oliveira, A.A., Laurance, S.G., Condit, R., Dick, C.W., Andrade, A., Nascimento, H.E.M., Lovejoy, T.E. and Ribeiro, J.E.L.S. 2005. Altered tree communities in undisturbed Amazonian forests: A consequence of global change? Biotropica 37: 160-162.Laurance, W.F., Oliveira, A.A., Laurance, S.G., Condit, R., Nascimento, H.E.M., Sanchez-Thorin, A.C., Lovejoy, T.E., Andrade, A., D'Angelo, S. and Dick, C. 2004a. Pervasive alteration of tree communities in undisturbed Amazonian forests. Nature 428: 171-175.Lewis, S.L., Malhi, Y. and Phillips, O.L. 2004a. Fingerprinting the impacts of global change on tropical forests. Philosophical Transactions of the Royal Society of London Series B - Biological Sciences 359: 437-462.Lewis, S.L., Phillips, O.L., Baker, T.R., Lloyd, J., Malhi, Y., Almeida, S., Higuchi, N., Laurance, W.F., Neill, D.A., Silva, J.N.M., Terborgh, J., Lezama, A.T., Vásquez Martinez, R., Brown, S., Chave, J., Kuebler, C., Núñez Vargas, P. and Vinceti, B. 2004b. Concerted changes in tropical forest structure and dynamics: evidence from 50 South American long-term plots. Philosophical Transactions of the Royal Society of London Series B - Biological Sciences 359: 421-436.Nelson, B.W. 2005. Pervasive alteration of tree communities in undisturbed Amazonian forests. Biotropica 37: 158-159.Phillips, O.L., Baker, T.R., Arroyo, L., Higuchi, N., Killeen, T.J., Laurance, W.F., Lewis, S.L., Lloyd, J., Malhi, Y., Monteagudo, A., Neill, D.A., Núñez Vargas, P., Silva, J.N.M., Terborgh, J., Vásquez Martínez, R., Alexiades, M., Almeida, S., Brown, S., Chave, J., Comiskey, J.A., Czimczik, C.I., Di Fiore, A., Erwin, T., Kuebler, C., Laurance, S.G., Nascimento, H.E.M., Olivier, J., Palacios, W., Patiño, S., Pitman, N.C.A., Quesada, C.A., Saldias, M., Torres Lezama, A., B. and Vinceti, B. 2004. Pattern and process in Amazon tree turnover: 1976-2001. Philosophical Transactions of the Royal Society of London Series B - Biological Sciences 359: 381-407.Phillips, O.L. and Gentry, A.H. 1994. Increasing turnover through time in tropical forests. Science 263: 954-958.Phillips, O.L., Malhi, Y., Higuchi, N., Laurance, W.F., Nunez, P.V., Vasquez, R.M., Laurance, S.G., Ferreira, L.V., Stern, M., Brown, S. and Grace, J. 1998. Changes in the carbon balance of tropical forests: Evidence from long-term plots. Science 282: 439-442.Pimm, S.L. and Sugden, A.M. 1994. Tropical diversity and global change. Science 263: 933-934.Weaver, P.L. and Murphy, P.G. 1990. Forest structure and productivity in Puerto Rico's Luquillo Mountains. Biotropica 22: 69-82.