getting to the root of forest carbon sequestration

I wanted to bring some attention to an important area of research lately: estimating the potential of the world’s forests as carbon sinks.  This research is important for two reasons (maybe others as well?):

  1. If we have better estimates of worldwide carbon sources and sinks we can better model what will happen in the future as these change.  Two of the largest sinks are the oceans and forests.
  2. If we have a sense of how much carbon the forests hold, we can decide if it is better to harvest some forests for bioenergy, or leave them untouched as carbon sinks.
Recently, a group including some researchers from CSU has published a study with more accurate estimates of how much carbon is sequestered, adjusting for the length of the day and how much light the forests receive.  They measured photosynthesis directly, rather than by remote sensing methods and found:
our work shows that leaves can remain green in the late summer and autumn, while photosynthetic capacity drops off, since photosynthesis is strongly controlled by day length. So although leaves may stay green in a warmer climate, it doesn’t necessarily mean that trees will take up as much carbon dioxide from the atmosphere as we assumed.

So the remote sensing methods of estimating carbon sequestration in forests was an overestimate:

Net primary production – the amount of carbon dioxide the Earth’s vegetation absorbs during photosynthesis, minus that released in plant respiration – drops from 58.7 petagrams of carbon per year to 56.7 petagrams of carbon per year, according to the PNAS study. That’s a downward correction of 3.4 percent. (1 petagram equals 1 billion metric tons.)

Another group from Boulder presents some data that somewhere, carbon sinks are absorbing more than our models predict:

What exactly is happening seems to be a bit of a mystery: as usual, things are more complex than we expected, and our models and estimates need to be refined and further adjusted.

Does anyone know more about this research and the methods and opinions on who is closer to the truth?  Do you know of relevant research that I haven’t mentioned?  I seem to recall some work from Oregon State and Canada on this, but I couldn’t find the relevant articles for this post.

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