Thread: Increased human carbon emissions lead to higher forest growth

some info on carbon absorbtion

http://earthobservatory.nasa.gov/Study/Fluxnet/

Because IPCC and other studies have shown that up to 25 percent of human-made carbon emissions may be taken up and stored by plants for use in respiration and growth, the Kyoto agreement allows nations to take credits towards their emission goals if they maintain or augment forest extent. However, scientists consulting on the Kyoto agreement were reluctant to sanction such credits because no one thoroughly understands the complexities of carbon exchange between the atmosphere and the biosphere. Consequently, scientists do not know if the creation of carbon sinks in the form of increased forests will do anything more than provide a temporary solution to the greenhouse gas problem.

In an effort to better understand carbon fluxes both on regional and worldwide scales, international scientists have created a mechanism to coordinate FLUXNET, a global network of research sites that measure regional carbon, energy and water vapor exchange between terrestrial vegetation and the atmosphere.

http://www.cru.uea.ac.uk/~markn/carbon/backgrnd.htm

Currently the global carbon (C) budget cannot be balanced. The CO2 released by fossil fuel and land-use changes is apparently greater than the amount remaining in the atmosphere and removed by the known sinks (Houghton et al., 1990; Houghton et al., 1992; Sundquist, 1993). The "missing carbon" is estimated to be ~0.23.0 GtC yr1, compared with 5.06.0 GtC yr1 from fossil fuels (Houghton et al., 1990; Houghton et al., 1992), although other estimates range up to ~4.7 GtC yr1 (Sarmiento and Sundquist, 1992). The inability to balance the C budget imposes considerable uncertainty on predictions of future atmospheric CO2 concentrations, possible future climate, and the debate on future C cycle manipulations (Dixon et al., 1994).

http://www.ornl.gov/info/ornlreview/...2/text/res.htm

Tree Growth in an Atmosphere Enriched in Carbon Dioxide

One of the longest studies of a forest tree species in an atmosphere enriched in carbon dioxide (CO2) suggests that in this environment trees absorb airborne carbon more efficiently and that some of the absorbed carbon ends up being stored in soil around tree roots. The ORNL study examined the response of trees to additional atmospheric CO2) from increased energy production using fossil fuels. Elevated CO2) levels may cause global warming and possibly disruptive climate change.

This study addresses a variety of questions. How do forest trees respond to rising concentrations of atmospheric CO2) from increased fossil fuel combustion, forest burning, and other sources? Do they grow faster? Do their trunks and branches become larger than normal? Are their leaves larger or smaller? Do they grow more efficiently even when deprived of nutrients and water? Will their response to elevated levels of atmospheric CO2) be to absorb and store more carbon from the atmosphere, slowing global warming?


ORNL studies of yellow poplar tree responses to an atmosphere enriched in CO2) have not found the dramatic growth seen in some studies with potted tree seedlings or irrigated and fertilized saplings—the so-called CO2) fertilization effect. The ORNL researchers found an increase in growth efficiency—the amount of stem wood produced per unit leaf area—in the yellow poplars. They observed a doubling of leaf photosynthesis—the use of sunlight to produce carbohydrates that provide energy for tree growth. However, the relative amount of leaf area that was produced was less, and the overall stem mass—the girth of trunk and branches—remained about the same. The additional carbon that was absorbed resulted in increased production of fine roots, rather than wood.

The increased fine-root production, Norby says, suggests that some of the additional carbon in the atmosphere may be eventually absorbed and stored in the soil rather than in trees. Fine roots, he adds, die and decay rapidly, but their residue is an important source of the carbon in soil. The possibility of increased carbon storage in soil is an important focus of DOE's new Terrestrial Carbon Processes Program, which aims at identifying and quantifying natural mechanisms of the terrestrial ecosystems that may affect trends in atmospheric CO2) concentration. Program scientists will develop the scientific understanding needed to model, predict, and quantify the role of terrestrial ecosystems in regulating the balance of global carbon.

http://www.pnas.org/cgi/reprint/0935903100v1.pdf

It would seem there is subtantial research and evidence that increased carbon emissions lead to increased tree growth, at least 25% and possibly a lot higher.