Anthony's Science Blog

Biogeochemistry Reading Group: Courtney Meier

February 4, 2009 – 5:33 pm

We have revived the biogeochemistry reading group! Like I said in an earlier post, the biogeochemistry reading group has been one of my favorite experiences as a grad student at CU. It has been cool to see it return. Although we’ve only had a few meetings, I’d say the group this semester is better than ever.

For our first guest of the semester, we invited my former labmate Dr. Courtney Meier. It was fun to have Courtney participate in the group and we read his recent PNAS paper on links between plant chemistry and ecosystem function.

Courtney got interested in the relationship between diversity and ecosystem function when he was looking at studies of plant diversity. He noticed that there were a lot of messy data sets and concluded that the species unit may not be the best way of looking at the interaction between plants and soils.

To examine this issue, Courtney used his expertise in chemistry to put various plant litter mixtures into different functional groups based on plant tissue chemistry. He found that indeed the chemical groupings of the plant litters provided a lot better predictive power for soil processes such as carbon efflux and nitrogen mineralization. Another one of Courtney’s interesting findings in the paper is that rare compounds do seem to have important influence on soil decomposition.

We spent a lot of our discussion talking about future extensions of Courtney’s study. There are many possibilities, but Courtney did note that one challenge to extending this work is that it’s difficult for other people to use the detailed chemical methods. But perhaps methods will improve in the future so that more people can investigate these questions.

Here are some of the extensions brought up in the discussion:

1. Could you get these kind of results with other species? Seems like it would be worth doing since the results came out so well in the case of Courtney’s paper. Again, the methods are hard, but if someone takes the time to do them, this could be a cool project.

2. It would be great to perform some focused manipulative experiments that would examine the specific compound classes (like phenolics, sugars, lignins, etc) to figure out which compound classes are the most important drivers of the various ecosystem processes and how they interact with one another. In Courtney’s study these things were occasionally confounded because, for example, plant tissue sugar and plant tissue nitrogen tended to co-vary. This could be worked out with some more experiments.

3. Are some of the results that Courtney observed in this study driven by Deschampsia? Deschampsia is a fast-growing grass that was one of Courtney’s four species in this study. It had particularly low chemical diversity. Put another way, are all plants with low chemical diversity chemically similar to Deschampsia? Perhaps their chemical makeup has a lot of basic plant tissue but not a lot of secondary compounds. More chemical analyses of other plants could help clear this up.

4. Sure would be great to do more with the microbes in this type of experiment. How are they responding (by species or functional group) to these different compounds and mixtures of compounds?

Finally, the popular topic of modeling reared its head. This time at issue: studies like Courtney’s emphasize the issue of non-additive effects in decomposition. Can these effects be modeled? Can we actually understand these complex effects or will they continue to be black-boxed? We’ll see.

It was fun having Courtney at our group after having shared an office with him for 4.5 years. It’s also great to see him doing so well with his science.