Waking up at 3am to collect dew, chasing after fog in the early morning on the C14 highway, and braving 74 kph wind storms to collect rain samples: that’s how a team of researchers from Michigan State University and Grinnell College spent their time at Gobabeb this winter.
The team, consisting of Professor Sarah Evans from MSU’s Kellogg Biological Station, Professors Kathy and Peter Jacobson from Grinnell College, and Robert Logan, Sarah Evans’s PhD student, worked at Gobabeb from June through August, putting in long days and nights. All four researchers have long standing connections with Gobabeb as researchers and trainers at the station.
Their research is part of a multi-year project focused on understanding how the decomposition of plants in arid and semi-arid grasslands contributes to global carbon emissions. As plants decompose, a lot of the carbon that used to make them up is converted into carbon dioxide that is emitted into the atmosphere. Since arid and semi-arid lands cover more than 40% of the Earth’s land surface, it is very important to know how much decomposition in these environments is contributing to carbon emissions if we want to accurately model global climate change.
For a long time, scientists assumed that decomposition was purely dependent on microbes like fungi and bacteria and that these organisms are only active during and after rainfalls. In recent years though, we’ve begun to realize that the picture is a lot more interesting. Research over the last decade has shown that purely non-biological factors like sunlight and high temperature can contribute to decomposition, independent of microbial growth. Even more recently, we are beginning to realize that non-rainfall moisture sources like fog, dew, and even high humidity can provide enough water for microbes to become active and grow, even without any rain (Jacobson et al. 2015). Taken as a whole, this means that deserts and semi-arid lands (with their high sunlight and low rainfall) likely contribute a lot more carbon dioxide into the air than we previously thought.
As part of Robert’s dissertation work, he installed an array of “sunlight manipulation shelters” at Gobabeb that will be periodically sampled from over the next two years to study the role sunlight plays in decomposition through a process known as “photodegradation.” Each shelter has a special kind of plastic sheet over top of it which selectively blocks certain wavelengths of sunlight from passing through them. Underneath each shelter is a collection of plant litter samples that will be collected every six months to look at changes in their mass, microbial community, and chemical composition to quantify the effect that sunlight has on the decomposition process. Noting a mild resemblance to the Very Large Array of radio telescopes in New Mexico, two Gobabeb staff members have christened it the “Gobabeb Very Small Array.”
Knowledge from this project will help climate scientists understand which factors are most important in driving arid land decomposition and eventually enable us to better predict and respond to climate change worldwide.