Reforestation, Afforestation, Soils and Carbon

Katy Hofmeister obtains soil samples for a carbon inventory by digging a soil pit and getting specimens from various layers.

Having read a few of the “what should we do with carbon in forests” papers, and leaving aside for now the “should we use forest products” discussion, I am thinking that by looking more broadly at forests, carbon, land use change, and other environmental and social factors, we can come back to that discussion with a better sense of context for a variety of climate and carbon interventions.

I’ve found that afforestation and reforestation are on everyone’s list of what can be done that are good for carbon sequestration. Afforestation has a couple of problems. It is land use change, and in many places there are no trees due to the climatic conditions, so it wouldn’t actually work in practice. But in some areas we do have a track record of success..say in the plains states, we could have a 21st century equivalent of shelterbelts (some of the ones from the 1930’s are starting to look pretty ratty).

But back to reforestation (that is, planting trees on forested land post some form of disturbance). We know how to do it in most currently forested places, and used to do it not that long ago (1980’s). In my career, I was fortunate to be involved in the Great Region 6 Reforestation Campaign during which nurseries, infrastructure, technology improvement and so on, were all aligned toward the goal of reforestation. Even Oregon State University had the Fundamental Fir Program. Most people agree with the idea and it is not disruptive to current economic and social structures (such as converting agricultural land to forest). But here’s an angle on it I hadn’t heard before with regard to soil carbon.

Here are some quotes from this Cornell University press release:

The study examined the potential to expand the soil carbon sequestration in reforested areas.

“The ability of U.S. forestlands to offset our emissions of greenhouse gases, including carbon dioxide, is decreasing,” said Hofmeister, who conducts research in natural resources and hydrology. “This is partly due to a backlog in reforestation projects on public lands that has been increasing for several decades.

“Nationwide, since 2000, less than 10 percent of forests are replanted after disturbances that eliminate forest cover. Reforestation would increase the soil carbon sink and go a long way to mitigating climate change.”


Sequestering carbon should be a strong component in fighting climate change, according to Hofmeister. “And, unlike other biospheric sinks, such as trees themselves – which can burn up in fires – soil carbon is quite stable,” she said.

Here is a link to the PNAS paper. You’ll note that the paper is national in scope and used remote sensing. Looking out at your neighboring forest, you would be able to imagine that the numbers for increasing soil carbon locally (over what would happen without intervention) depend greatly on the soils themselves, climate and water availability, the kind of disturbance (think volcano, fire, logging) and how easily (or if) the forest would naturally regenerate. If one were to look at reforesting as a carbon investment and prioritize the areas where you would get the biggest carbon bang for the buck. Still, it’s interesting to think about.

8 thoughts on “Reforestation, Afforestation, Soils and Carbon”

  1. “Reforestation” is always linked with clearcutting, in some people’s minds. Even though clearcutting has been banned in Sierra Nevada National Forests, some eco-groups continue to be against replanting, in favor of “Whatever Happens”. I think it is a knee-jerk response that ignores site-specific conditions and realities. Yes, we have seen forests in Yosemite that haven’t grown back, mostly due to re-burns. Now, seed sources are scarce and even chaparral has a tough time growing there. There’s no organic matter in the soil to help increase the moisture-holding capacity. With humans around, “natural succession” has broken links, and should not be relied upon for ‘restoration’.

    • I think it goes back to the old argument about what is “natural”. Some days, human influences and climate change have totally disrupted Nature. Other days, we must step back and allow what happens to happen because it’s “natural.” It’s just confusing to me as they seem inconsistent views often held by the same people.

  2. should forest policy be focused on likely outcomes or the extremes?

    “reburns” and reforestation failure certainly happen but they are fairly uncommon yet seem to loom large in the minds of some people.

    • Forest policy be focused on desired future conditions, based on the triple bottom line: economic, environmental, and social factors. Not one, not two, not solely carbon or climate — all three.

    • Frankly, the likely outcome is human-caused wildfires. Shouldn’t we consider that fact in our decisions, instead of an illogical belief in the promise of pre-human landscapes?

      Here in California, not thinning snags after a wildfire dooms that piece of land to be unproductive and ugly, until the humans decide to craft resilient forests, like another set of historical humans did in the past. Preserving Sierra Nevada forests without management is resulting in disaster. Historical accounts show ample old growth and fire resistant landscapes. Different species compositions. Less density and less brush.

      There will be no pre-human landscapes in California. Better get used to it.

    • I disagree that they are “fairly uncommon.” It depends on where you are. I think if you drove by something like say the Hayman Fire, or lived there it would probably loom large in your mind as well. Two thoughts:
      1) it’s easier to see “no little trees” on the ground than from satellites.. so does the current trend of using satellite data for many studies “not see” things that people on the ground observe?
      2) Even if they were “uncommon”, say < 50% (?) of burned areas, does that mean it would not be a good idea to get trees going sooner to suck up carbon and for other reasons (habitat, soil protection and so on)?
      3) I'm checking with the FS on their current refo backlog using their definitions. For some reason I couldn't easily find it on the internet.

  3. Hmmmm, maybe we need a new ‘measurement’ I’d like to call it ‘Human-caused Fire Return Interval’. We should not ignore how often human-caused fires happen in our western forests. Such wildfires will never go away, or be mitigated by inaction. The folks who worship Gaia don’t want to talk about this important issue. In fact, it is the “elephant in the room” but, preservationists have no way to address such impacts to unnaturally-dense, highly-flammable, fire-suppressed species compositions. Pretending that some fictional entity will save us from ourselves is the ultimate in forest irrelevance.

  4. Many of our forested ecosystems have been heavily altered – and many of the areas that burn are previously harvested sites. We have altered the species composition, the landscape pattern, the soils (think windrows and hot burns), and many other things. We have also altered fire occurrence. We also have diseases that have come in from other places (think white pine blister rust, sudden oak death and Port-Orford-cedar root disease), and we have climate change. We also have many areas with “off-site” trees (many of which don’t produce seed, thank goodness). Many of the old-growth forests in the Pacific Northwest were thought to have established during the “Little Ice Age”. We can’t go back. Natural regeneration is very cost-effective, but we may have eliminated seed sources through our prior management, and it may not be resistant to disease. Shade (from tree crowns) can also be one the best herbicides that we have to deal with invasives. It’s just not that simple.


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