Forest ecosystems are elementary for a climatic equilibrium. Countries such as China have acknowledged this fact; For years they have been carrying out extensive afforestation programs to compensate for their rising CO2 emissions. As part of the global carbon cycle, forests absorb about 45 percent of the carbon from the environment and bind it in the soil and as biomass for long periods. At the same time trees can absorb or release carbon in the short term.
So far, however, little research has been done into whether the number of tree species in a forest affects the carbon cycle in the ecosystem. A team of researchers from Switzerland, Germany and China has now collected extensive data on 27 forest areas in Zhejiang Province in subtropical Southeast China for a period of six years. The researchers, including some of UZH, investigated the amount of long-term stored carbon (C-stock) and the carbon exchange in the short term (C-flux). The forest allocations were chosen to represent a wealth gradient ranging from three to twenty tree species and an age category of 22 to 116 year old tree stands.
Each extra type contributes 6.4 percent higher carbon stocks
Previous afforestation efforts in China have already significantly contributed to reducing the increase of carbon dioxide in the atmosphere. "China has restricted its program to monocultures," explains Bernhard Schmid, professor of environmental sciences at the University of Zurich. "We wanted to know whether a combination of tree species compensates more carbon than just a single tree species."
The researchers discovered that species-rich forests have a faster carbon cycle than those with only a few species. With increased species richness, more carbon is stored both above and below ground in trunks, roots, dead wood, fungi and soil. Estimates from the team of researchers have shown that 6.4 percent more carbon can be compensated with each additional tree species in an allotment. In addition, older trees collect more carbon than younger ones.
$ 300 million a year in the atmosphere
"Projected across China, extra carbon worth $ 300 million per year could be absorbed from the atmosphere from 1977 to 2008 as species-rich allotments with 10 tree species were planted instead of monocultures," says Bernhard Schmid.
In order to reduce the CO2 impact in the atmosphere, the researchers therefore propose to plant as many species-rich tree mixtures in global reforestation programs as possible instead of using monocultures. The goals of the fight against the greenhouse effect and the prevention of further loss of biodiversity in forests could therefore be achieved simultaneously.
Material delivered by University of Zurich. Note: content can be edited for style and length.