There have been hopes in the scientific community that as the increased levels of carbon dioxide in the atmosphere warmed the planet’s climate, the forests would grow and increase their carbon storage capacity. But new research suggests that another factor — increased litterfall — may turn about any increased carbon storage.
Litterfall is any dead plant material, such as leaves, bark, and twigs, which fall to the ground. Increasing the amount of litterfall may, according to the researchers who were led by scientists from the Centre for Ecology & Hydrology and the University of Cambridge, UK, affect the amount of carbon stored in the soil.
The research team studied results from a six-year experiment in a rainforest at the Smithsonian Tropical Research Institute in Panama, Central America. The project was focused on the study of how increases in litterfall may affect carbon storage in the soil.
What they found was that the extra litterfall triggers an effect known as priming. Priming is when fresh carbon from plant litter provides energy to micro-organisms which in turn stimulates the decomposition of carbon stored in the soil.
“Most estimates of the carbon sequestration capacity of tropical forests are based on measurements of tree growth,” said lead author Dr Emma Sayer from the UK’s Centre for Ecology & Hydrology. “Our study demonstrates that interactions between plants and soil can have a massive impact on carbon cycling. Models of climate change must take these feedbacks into account to predict future atmospheric carbon dioxide levels.”
The study concludes that even though forest growth may allow the trees to store more carbon, the loss through the soil could unbalance that increase.
Their estimates suggest that a 30% increase in litterfall could release approximately 0.6 tonnes of carbon per hectare from lowland tropical forest soils each year.
This estimate amounts to more than the estimates of increased carbon storage in trees.
Given how much of our planet is covered by tropical forest, and the resulting level of carbon stored in the soil, such an increase could have dramatic and devastating global consequences.