Duke University Study Throws Cold Water On Carbon Sequestration Hopes

[hatrack]

SEATTLE -- A futuristic Duke University simulation of forest growth under the carbon dioxide-enriched atmosphere expected by 2050 does not reinforce the optimism of those who believe trees can absorb that extra CO2 by growing faster, said a spokesman for the experiment.

During seven years of exposure to carbon dioxide concentrations 1½ times higher than today's, test plots of loblolly pines have indeed boosted their annual growth rates by between 10 and 25 percent, found the researchers. But "the highest responses have been in the driest years, and the effect of CO2 has been much less in normal and wet years," said William Schlesinger, a professor of biogeochemistry and dean of Duke's Nicholas School of the Environment and Earth Sciences. These counterintuitive findings suggest that nitrogen deficiencies common to forest soils in the Southeastern United States may limit the abilities of loblolly pine forests to use the extra CO2 to produce more tissues as they take in more of the gas, he said.

EDIT

Apart from the impact of nitrogen deficiency and drought, the scientists have found some indication that pine tree growth declined over the years at the high CO2 levels, he said. The trees bathed in high CO2 also added more fine roots, which Schlesinger suggests is just another indicator of low nitrogen. "If trees don't have a lot of nutrients they grow a lot of roots looking for them," he said. Meanwhile, some other species in Duke's CO2-bathed forest plots have grown at faster rates than the loblolly pines, scientists report. Still-unpublished data shows 70 percent growth increases for poison ivy, according to Schlesinger.

There is also evidence that the extra carbon dioxide has induced more underlying rock to weather into soil through dissolution by CO2-produced carbonic acid. While that action would also remove carbon dioxide from the atmosphere and "store" the remnants in the added soil, the impact would be "trivial" compared to expectations from boosted tree growth, Schlesinger said."

EDIT

http://www.evworld.com/view.cfm?section=communique&newsid=5055

[TreasonousBastard]

1. Heard some preliminary...

findings from this study a few years ago. Didn't seem too hopeful back then, iirc.

I am kind of curious why they used that sterile soil, though. Reforestation would tend to be toward bringing back wilderness areas where the soil hasn't been so depleted.

Bigger problems are the clearcuttings in the Amazon basin and subsaharan Africa. The amount of biomass there is incredible and really can't be compensated for by planting a bunch of evergreens in northern areas.

We could, of course, think about covering one or two states with kudzu and moving pig and chicken farms in to fertilize them.

How long would it take for kudzu to entirely cover Texas?

[hatrack]

4. As to why they used "sterile soil"

Well, they sure aren't going to give up the best bottomland for an experimental forest when it could be planted in corn or tobacco, that's for sure! ;-)

That's something people always seem to forget about forests - nutrients are utilized to the maximum degree possible in any natural forest environment. What you see growing there is the maximum possible growth, with canopy trees and understory competing with moss, grasses, shrubs and everything else to use up all available nutrients.

It's an environment in which nutrient utilization is already maxed out.

[On the Road]

2. I Heard a Suggestion to Take Crop Leavings

like corn stalk after harvest, ship them out to a lifeless part of the ocean, and sink them. Turned out it would have a surprisingly large effect on greenhouse gases.

Another sequestration idea is to seed large parts of the Indian Ocean with nutrients that would encourage the growth of plants (plankton or algae, I forget) which would not only take carbon out of the atmosphere, but then die and bring it to the bottom of the ocean.

Problem is that even if relatively lifeless parts of the ocean are chosen, the macro effects are unknown. But if climate changes start to accelerate, pressure might start to build to try some more experimental solutions.

[enki23]

3. and what would you use to replace the lost nutrients for the cropland?

that's about the worst idea i've ever heard. we'd have to use even *more* fossil fuels to create even more fertilizer to make up for the crop leavings we shipped out to sea (using fossil fuels to do the shipping.)