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Atom FeedCarbon sequestration is the trapping of atmospheric carbon (carbon dioxide) into some form where it can stay for decades. Carbon sequestration occurs naturally by the actions of plants, especially long-lived vegetation, and in certain soils, where it’s deposited as slow-decaying organic matter. Plants use sunlight to convert atmospheric carbon dioxide into the chemical that make up plant material–simple sugars, to start with, then starches and more complex chemicals when added to other nutrients.
Why is this of interest in wildlife management or prairie restoration? The obvious reason is climate change caused by increasing carbon dioxide levels. Carbon sequestration by changes in management of both public and private lands is one way to get carbon dioxide out of the atmosphere and into plant materials. Many of the things a land manager might do to promote wildlife or restore an original ecosystem (forest or grassland) will have multiple benefits…including carbon sequestration.
Everything we consider wildlife is on the wrong side of the carbon cycle, as we are…from the snail to the white-tail deer, they all inhale oxygen and exhale carbon dioxide. Only plants work the other half of the cycle. Looking out on a piece of land, plants are what we notice–how much plant cover and what kind: grass, forbs, shrubs, trees, etc.
The carbon sequestration potential of different types of habitat has only recently been considered, and have not been well-researched. It’s known that long-lived trees sequester a lot of carbon throughout their lives–and using wood products from cut trees removes that carbon from the atmosphere as long as that wood is protected from decomposition (by its use in construction, for instance.) However, it’s also known that when cut or otherwise killed, there’s an immediate burst of carbon dioxide release due to decomposition of the tree’s underground portions. Forest and scrub fires are worse, converting the above-ground stored carbon to carbon dioxide by burning, as well as killing the trees and shrubs so that soil deposits are also lost. It’s known that wet soil (having less or no oxygen) stores carbon better than dry soils (especially if they’re opened to oxygen by cultivation.
Wrede’s 2005 book, Trees, Shrubs, and Vines of the Texas Hill Country, published by Texas A&M Press, said that one acre of “thicket” in the Texas hill country would sequester all the carbon produced by driving a car 26,000 miles. But I haven’t seen any figures on central Texas riparian woods, or on the southern prairies in restoration projects. Still, comparisons of old prairie (where it exists) indicates that native prairie does indeed sequester more carbon than shallower-rooted non-native pasture grasses (and far more than lawn grass, which is not useful at all as a carbon sink.
Initially, when we started on this project, one of my goals was to have the grassland entirely empty of woody plants. However, with the information about the value of woody plants for carbon sequestration, I’ve been considering whether increasing the fraction of the 80 acres that has some woody plants might not be a better idea. Not in solid forest or even “thicket,” and certainly not in a takeover of Ashe juniper, but in clumps here and there–which (where we have them) do add habitat for nesting birds. A sort of savannah effect, in those areas where the cedar elm (in particular) keeps sprouting back up.
We’ve also been looking at trees adapted to a hotter, dryer climate–trees from southwest of here–especially for long-lived ones of a size to store significant amounts of carbon–as replacement trees to plant into the riparian woods. We had long considered encouraging some trees in the southwest meadow, especially along the margins of the existing west woods, to “thicken” that habitat for wildlife, and in the northwest meadow to fill in an angle between the west woods and the main creek woods with more desirable trees than the juniper. (Not that the juniper deserves its bad reputation, but we have plenty of them.)
I see several possibilities for land managers in the future.
First, fire is a less desirable management tool when carbon sequestration becomes a goal. For all the good that fire can do in some circumstances, it quickly changes stored carbon to atmospheric carbon dioxide (besides contributing to already poor air quality and thus to human disease.)
Second, carbon sequestration benefits wildlife and also restoration projects, as the methods of sequestration fall in line with other management activities. Increasing coverage of native plants (either woody plants or native grasses) improves habitat for wildlife and tends to create soil conditions that trap more carbon in the soil…while at the same time improving the soil’s water holding ability and thus water quality downslope. Erosion control projects using native plants and natural pond protection/development (including seasonal wetlands of shallow water) produce damper soils that slow decomposition of organic materials.
Third, carbon-sequestering is already providing an new income stream for landowners in the right environments, if they can gain certification as a carbon sequestration project…carbon credits are marketable.
Fourth, the carbon sequestration potential of well-managed small acreages will increase as more and more land is built over and paved. And thus the managers of smaller and smaller plots will need to consider carbon sequestration in their management practices.
There are always tradeoffs. Each project has a unique set of conditions. What is right for our 80 acres certainly won’t be right for every 80 acres (let alone 40, or 20, or 10, or 5 acres. Each landowner/manager will need to consider carefully what the tradeoffs are for each individual piece of property. But we all need to do that.
Comment by Martin LaBar — June 14, 2010 @ 5:34 am
You have certainly thought this out.
I checked the Wikipedia on “Carbon sequestration.” The article said that there is more Carbon sequestered in soil than in plants, which was a surprise.
Comment by elizabeth — June 14, 2010 @ 8:14 am
In my mid-twenties, I read a book on the Appalachians, describing a fire in West Virginia where clear-cutting had allowed the forest soil to dry out–and it burned down to the bare rock. That was my introduction to carbon sequestered in soil, though it wasn’t phrased that way then. Then I read about peat as a fuel, and made the connection to coal (ancient soil-carbon.) Later, in the county where I now live, a history of the county mentioned a great fire after plowing had opened the prairie soil and allowed it to dry…and the soil burned…it was basically peat. It burned for months.
I already knew that the tall-grass prairie soils had been deep and often moist deep below the surface even in drought–and had not burned in the great fires on natural prairie. That moisture protected them, preserved the very deep root structure of the native grasses and forbs. And these soils were fertile precisely because they were rich in organic matter–stored carbon.
More recently, in the last few years, research on forest soils in tropical forests showed that there was a huge loss of sequestered carbon immediately after a tree was cut–outgassing from the soil–due to the rapid decomposition of organic matter in the soil–the tree’s roots and other detritus now available for decay and consumption by oxygen-breathing organisms.
Some plans for carbon sequestration include reforestation intended for timber production, and though I agree that wood products used for furniture, buildings, etc. are sequestering that carbon, I’m not so sure about the balance. Harvesting timber and then turning it into usable wood, transporting that wood long distances, shaping that wood with modern tools–all these require oxygen-burning and carbon-dioxide producing machines. I haven’t seen an analysis that takes into account the full carbon footprint of harvesting plantation-grown trees (which is obviously better than continuing to destroy original forests, but may not be ideal for carbon sequestration over the next 200 years.)
Comment by Adrian — June 15, 2010 @ 2:44 pm
Hello from an urban conservationist/gardener in the Chicago area.
Your post is very interesting, and your point is well taken. I notice once again that all landscape management is local. I can see that in a dry area, fire might not be the best tool. Here in Illinois we do rely on it: our conditions are decidedly wetter, and many of our prairie and savanna plant species do better after a managed burn–some require the heat to germinate.
Consequently, I am of the opinion that managing for carbon sequestration involves trade-offs. Since Illinois prairie sequesters more carbon than Illinois woodlands, and the woodlands are always trying to gain ground, burning might be better in terms of overall sequestration–for us. I think there might be no blanket strategies.
Comment by elizabeth — June 15, 2010 @ 5:39 pm
I agree: in a changing climate situation with implications for the whole planet, managers must be prepared to use the best strategy for that piece of land–and also be prepared to shift strategy if conditions require it. And definitely, carbon sequestration requires tradeoffs. What was the best combination of actions fifty years ago or a hundred years ago may or may not be best now, or fifty years from now. Conditions change; we must change with them.
In your climate, with damp soils that can protect the crowns and buried seeds of your high floristic quality plants, fire will remain a viable tool longer than in dryer climates…as long as you are able to get burn permits. And that will depend on your neighbors’ perception of the risk to them in a prescribed burn in your location.
Fire was recommended here, and is routinely used here, in managing the prairie remnants we have as well as pastureland that is no longer genuine prairie and grows brush because it is degraded. However, in the past five years of increased temperature and drought conditions (except for the six months from September ’09 to March ’10, when we had floods instead) we saw increased wild fires and also prescribed burns gone wrong. Along with the climate change, there’s been steadily increasing development and population growth, with fragmentation of large ranches (which could spare a few hundred acres if the fire didn’t stop where it was supposed to) into smaller properties, all bordering some developed area. Uncontrolled fires (including some started as prescribed burns) have menaced new subdivisions and destroyed homes. Our county had a total burn ban for months last year; so did neighboring counties.
It would be helpful to have solid research on the magnitude of the carbon cycle elements in all climate and habitat types, but as climate change denial is still strong, that research hasn’t been done and may not be done in time to aid management decisions. For instance, where we are was an interlaced pattern of plant communities when white colonists first came: riparian hardwoods along permanent water courses where the soil was deep, “canyon community” junipers and other species on steep slopes, tallgrass prairie, midgrass prairie, areas of juniper/oak/shortgrass savannah growing on very thin soils on rock. The remnant native grasses on our place covered the gamut from true shortgrass species to midgrass to one remaining tallgrass (we’ve restored three more.)
Back when I first studied open land management, one of my profs said “Manage the water well and the land will manage itself.” In the first years we owned this place, we did the usual things to slow or halt surface runoff, promote absorption into the soil, etc. We’re still doing them; erosion has slowed, except at the creek (which runs across the short axis and carries flash floods from upstream of our place.) But we can’t stop the inflow of plants and animals moving north with the change in climate or the changes in rainfall pattern that benefit a different plant community than used to exist here. And so far we haven’t been able to stop the steady, and increasingly fast, loss of habitat and plant cover to development.
It’s hard decisions for all thinking land managers.
Comment by Tom Skupham — July 18, 2010 @ 2:10 pm
At last, a thinking person who believes growing plants & trees in particular help to reduce atmospheric Co2. if only our Leaders thought along theese lines.In the United Kingdom the Politicians think that windmills for power generation will Solve this Problem.In the past We had a Wooden Navy, Thousands of Oak trees must have been felled to build them ,but not many Have been replanted. lots of Conifers have ,50 years ago if some of them had been Hard woods such as Oak ash &walnut, some furnature grade Timber would most probably have been ready for Harvest
as a now retired man with children & Grandchildren I will Get Off my Soap box
Comment by elizabeth — July 18, 2010 @ 3:45 pm
The planting of fast turnover conifers after cutting hardwood forests is a major problem everywhere. My husband’s family leased land to a timber company–and away went the old southern hardwood forest, replaced by pines that could be harvested in a couple of decades. Away also went the hardwood forest understory of plants equally valuable but less known in modern times. I’ve seen beautiful old hardwood trees in the UK, and wish that more were being replanted instead of those rows and rows and rows of pines or whatever they are. You’re quite right–the hardwoods sequester carbon longer, and then you’ve got more useful (and more varieties of useful) wood to work with. One of my old books on trees discusses the qualities of the various woods that were native to North America…not just which gave the most BTUs when used for fuel, but which were best for specific purposes like chair legs or axe handles or small tool handles. Those were the books that made me realize how different woods are.
Where we are, the native prairie sequestered a lot of carbon in the soil and we’re reintroducing that, as it’s more resistant to drought than woodland around here. Every drought (like the recent one) we lose trees, but the old prairie plants recover when it rains. We’re doing what we can to preserve the trees we have and we do plant new ones (mostly oaks native to prairie groves) but it’s heartbreaking when one we’ve finally nursed up to five or six feet tall dies in a drought. (The best oak for here is very, very slow to start…it’s maybe a foot tall for four or five years, as it develops its initial root structure, and during that time is very susceptible to damage above ground as it hasn’t a thick bark yet. Once it’s ready, though, it shoots up and becomes a large–for us–tree. )
Comment by Biobob — October 21, 2010 @ 11:30 pm
Good ideas. The best thing you can do is remove constant artificial perturbation from the system. In general, stability = more diversity and less dominance by few. I suspect fire is overused – it would be nice to find out exactly how often any particular climax habitat in central Texas actually burned, but I doubt we will ever know for sure.
Diversity by itself is not especially useful. Rather than how long the tail of the normal curve is (which is a function of sample size) ecologists often use the relationship of dominance vs diversity. Disturbed habitats have higher dominance by fewer species vs undisturbed. Increasing the number of micro-habitat types goes hand in hand with increasing carbon sequestration. Smaller landscape mosaics mean more species per hectare. Think lots of small patches.
In general, natural terrestrial ecosystem gross organic carbon sequestration increases the further from the tropics one moves. It’s simply a function of biotic cycling of the organic matter as related to the environment. Less time for decomposition/consumption by bacteria and fewer species / niche exploitation as one moves away from the equator. One of the most striking observations made about tropical vs temperate ecosystem is the fast cycling of organic materials in the tropics versus huge accumulations of organic materials in various stages of decomposition in temperate systems. In the tropics, most organic carbon is in the form of living biomass and in temperate regions, much more can be in decomposing materials. When you visit ‘undisturbed’ temperate forests, the amount of dead wood and soil organics is staggering.
It takes fairly long time before habitats reach “climax” condition and this is especially true with soil organic carbon.
All this has very little to do with climate change, however, and a tremendous amount to do with your aims for maximal diversity on your land. There is absolutely no reliable factual basis to conclude that humans // CO2 have anything whatever to do with recent “warming” over large areas. I reserve judgment. We will see as we learn more, since we simply do not possess the data needed to form conclusions. The vast majority of recent supposition/alarmism/hypothesising/hand wringing etc concerning ‘global warming’ simply has no rational basis at this point.
Biobob PhD Aquatic Ecology