Plant litter decomposition is a large source of carbon dioxide to the atmosphere, releasing 8-10 times more CO2 annually than fossil fuel combustion.  Typically we can use plant litter quality features like lignin concentration (lignin is the stuff that makes wood hard) and environmental factors like evapotranspiration to predict litter decomposition rates. However, we underpredict the decomposition rates in desert systems when we try to use these same factors.

Goofy Looking Biologist trying to do some field work at the Desert Botanical Garden

Usually, microbes decomposes our plant litter in ecosystems with water present, but here in the desert, it’s been discovered that some other factor can influence how plants decompose, sunlight! So we had an experiment that lasted nearly two years in the Desert Botanical Gardens in Phoenix, AZ that attempted to measure how different wavebands of sunlight influence the rates of decomposition.

Samples attached to soil surface

In the photos above, you’ll see these litterbags that are filled with plant litter. We used three different types of litterbags. One litterbag had a top that let in all the sunlight, one blocked ultraviolet (UV), and one blocked UV and blue sunlight.

One of eight field plots

This experiment had four different harvests, or times that we bring in a certain amount of the samples so we can track how much decomposition is going on. We measure the amount of decomposition by measuring the amount of mass that is lost from each sample.  We also may measure many other things on those plant litter samples like the amount of microbes (bacteria and fungi) present, how active the microbes are or the chemistry or the quality of the plant litter itself.

Weighing plant litter

The experiment concluded in 2017 are we have started presenting and publishing some of that data. Below is a poster that I presented at the 2017 Ecological Society of America meeting in Portland, Oregon.

 

Papers published on this project

Day T.A., Bliss M.S., Tomes A.R., Ruhland C.T., & Guénon R. (2018).  Desert leaf litter decay: coupling of microbial respiration, water-soluble fractions and photodegradation. Global Change Biology. In Press.