Wednesday, 18 September 2013

CO2 is good for you: And good for Giant Pandas, too/

We have recently had many reports that the rising atmospheric CO2 is increasing the biomass; helping with increasing food supplies for man and beast.

A few examples:

  • A 2012 survey of experimental plots in South African savannas — where fires, rainfall, and herbivore pressure have remained constant for decades — shows large increases in woody plant mass, which the authors primarily attribute to the so-called “CO2 fertilization effect,” the enhancement of plant growth caused by increasing atmospheric carbon dioxide. (link)
  • Increased levels of carbon dioxide (CO2) have helped boost green foliage across the world’s arid regions over the past 30 years through a process called CO2 fertilisation, according to CSIRO research. (link)
  • EucFACE was established in 2010 following recommendation to the Commonwealth to understand how rising atmospheric CO2 concentration and CO2 fertilisation affects tree canopy processes and soil and ecosystem function in an Australian native woodland. (link)
Now we find a new study from China where the authors note that dwarf bamboo (Fargesia rufa Yi), which grows in the understory of subalpine coniferous forests in China, is one of the main foods of the giant pandas that live there and they wondered how the ongoing rise in the atmosphere's CO2 concentration might impact these small bamboo plants.

As reported by CO2 Science (link)

Li, Y., Zhang, Y., Zhang, X., Korpelainen, H., Berninger, F. and Li, C. 2013. Effects of elevated CO2 and temperature on photosynthesis and leaf traits of an understory dwarf bamboo in subalpine forest zone, China. Physiologia Plantarum 148: 261-272.

What was done
Seeds of the dwarf bamboo plants were collected and sown in seedbeds where the resultant seedlings were allowed to grow for four years, after which healthy seedlings of a uniform size were transplanted into 120 20-L pots filled with surface soil taken from the natural forest floor. Then, starting in May of 2010, the planted pots were placed within eight enclosed-top growth chambers constructed from materials having a transparency of 85% (walls) and 82% (tops), where they grew until the end of the study in September 2010 in air of either ambient or double-ambient CO2 and either ambient or ambient +2.2°C temperature, while numerous measurements were made on the young trees over the course of the 150-day experiment.

What was learned
The six scientists report that "the light-saturated net photosynthetic rates of the dwarf bamboo increased by 57.6% under elevated CO2," while in the case of both elevated CO2 and elevated temperature together, the increase in net photosynthesis was 36.9%. They also report that they "found no evidence of photosynthetic down-regulation in the dwarf bamboo." In addition, they say "there were no significant reductions in the nitrogen concentration based on mass in the dwarf bamboo," and that "there were even increases in the N concentration based on [leaf] area when exposed to elevated CO2." And they speculate that "the lack of observed photosynthetic down-regulation may be related to this result."

What it means
In the concluding paragraph of their paper, Li et al. write that the dwarf bamboo plants could adjust their "physiology and morphology to enable the capture of more light, to increase water use efficiency and improve nutritional conditions." However, they also indicate that elevated temperature had just the oppositeeffects on water use efficiency and nutritional traits of leaves. But in the end, they report that "the combination of elevated CO2 and elevated temperature showed no significant interaction effect on the nutritional traits of leaves." And, therefore, their ultimate conclusion was that if and when "the dwarf bamboo confronts warmer climate for a long term, elevated CO2 will be beneficial," as it will lead to the production of more equally-nutritious dwarf bamboo tissue.

Read more at CO2 Science

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