More rainfall in wet seasons promotes more carbon dioxide released from soil

Chinese researchers have disclosed that more rainfall during wet seasons promotes the release of carbon dioxide from the soil, according to a recent research paper published in the journal Ecology and Evolution.

The researchers from the South China Botanical Garden under the Chinese Academy of Sciences (CAS) conducted the precipitation manipulation experiment to simulate a delayed wet season and a wet season with more rainfall over a three-year period from 2012 to 2015. They hoped to learn how seasonal precipitation changes affect soil respiration, especially in seasonally dry tropical forests.

In the delayed wet season, they reduced throughfall by 60 percent in April and May and irrigated the same amount of water into the plots in October and November to extend the end of the wet season. And in the wet season with more rainfall, the researchers irrigated 25 percent more annual precipitation into plots in July and August.

The results showed that the delayed wet season remarkably increased monthly soil moisture by 30 to 54 percent during the dry season, while the wet season with more rainfall did not significantly affect monthly soil moisture.

In 2015, the delayed wet season significantly increased leaf area and soil microbial biomass, but decreased fine root biomass, said the paper. This demonstrated that the delayed wet season accelerated the emission of carbon dioxide from the soil microbes.

Meanwhile, the wet season with more rainfall significantly increased litter decomposition and accelerated the emission of carbon dioxide from the soil.

Thus both a delayed wet season and a wet season with more rainfall will have a significant impact on soil respiration and its ecosystem.

The precipitation manipulation experiment was conducted at the Xiaoliang Research Station for Tropical Coastal Ecosystems of the CAS in south China's Guangdong Province.（Xinhua）