CO2 increases water holding capacity

Dr. Feike Dijkstra, expert in biogeography at the University of Sydney (Australia) and colleagues published this new discovery in the scientific journal Nature in early August.

According to the researchers, when the climate warms the Earth, the grasslands will become more dry and have a higher risk of fire. However , once the level of carbon dioxide (carbon dioxide) increases, it will compensate for the loss of water because plants can use water more efficiently. Dijkstra said that this is one of the few studies aimed at understanding the combined effect of warming Earth and increasing CO ₂ levels on water balance in plants and in grasslands sold. drought.

In fact, the grasslands will become drier due to more evapotranspiration when the climate heats up. However, some evidence suggests that an increase in CO ₂ levels may reverse this phenomenon due to enhanced plant water use efficiency. The reason is that plants will lose water when opening air holes (small holes under the leaf surface) to absorb CO2 for photosynthesis. When CO ₂ concentration is increased to a high level, plants do not have to open air holes, so they lose less water. 'As CO2 levels rise and the air warms, that level of CO2 will completely reduce the effects of temperature rise ,' concluded Dr. Dijkstra.

Scientists are doing experiments in the field

Through experiments, Dr. Dijkstra and colleagues studied a semi-arid grassland in Wyoming state, the western mountainous region of the United States. There are two types of C4 grass (warm season grass) and C3 grass (cold season grass) alternating. Mr. Dijkstra said cattle farmers prefer the C3 variety because they are rich in nutrients. The team examined the impact of global warming and increased CO ₂ concentrations calculated by the Intergovernmental Panel on Climate Change (UN) affecting the region.

Accordingly, they divided 20 plots, each with a diameter of 3m, of which 5 lots were control areas, 5 other lots had CO ₂ levels up to 600 parts / million, 5 other lots had temperature conditions. increased from 1.5 to 3 degrees Celsius. And the remaining 5 lots including CO ₂ and temperature all increased. Around the site is a pump system of CO2 gas and an infrared heater to increase the temperature. Thereby the researchers found that the overall water use capacity of the pasture was higher than expected.

In particular, the measured biomass and water content of the soil collected within 4 years showed that higher temperatures combined with increased CO ₂ concentrations help maintain the water content in the soil. The drought-induced effect of increased temperatures has been removed because the water in the trunk is used more effectively by higher CO ₂ levels.

Kevin Goss of Future Farm Industries CRC said Australia and the United States have had many collaborative technical research projects in livestock areas. According to Mr. Goss, the temperature and CO ₂ levels in the study are related to global climate conditions over the next 75-90 years. Future Farm Industries CRC is currently involved in the selection and development of C3 and C4 grasses, which have good drought tolerance and high productivity.

As a result, both types of grass use water more efficiently in environments with higher CO ₂ concentrations. In particular, C4 grass thrives in higher temperatures. Moreover, this grass prevails in environments with high temperatures and CO ₂ concentrations. 'Increasing CO ₂ under increased temperature affects the structure of the flora' , Dijkstra said.

According to Dr. Dijkstra, a large area in Australia is covered by alternating grasslands between C3 and C4 grasses. Therefore, the study's findings are quite relevant to the grasslands of this country and help scientists can create similar effects with grasslands to continue to preserve them. Besides, Mr. Dijkstra also wanted to understand the impact of high temperature and CO ₂ on nutrient circulation. This is a factor that has a long-term impact on crop yields, especially in limited nutrient areas.

In Australia, the land used longer has low phosphorus content. Dr. Dijkstra's preliminary study shows that in the event of global warming, the plant's phosphorus content will be less and this is what scientists study in breeding areas. more ideas.