Some recent(ish) papers

October 4, 2012

Some recent-ish papers of mine, that is. Although I didn’t enjoy my last post-doc in Montpellier a whole lot, there was a small amount of output from it, which probably deserves recording. So here goes.

I. Ross, L. Misson, S. Rambal, A. Arneth, R. L. Scott, A. Carrara, A. Cescatti, L. Genesio (2012). How do variations in the temporal distribution of rainfall events affect ecosystem fluxes in seasonally water-limited Northern Hemisphere shrublands and forests? Biogeosciences 9(3), 1007-1024. PDF

This was a paper that was started by Laurent Misson, who worked at CEFE until his death in a mountaineering accident in March 2010. I picked it up, redid and revised the analysis and rewrote the paper, and we published it as a sort of tribute to Laurent.

The motivation for the analysis in the paper is that projections of future climate change seem to suggest that, even if total rainfall might not change all that much, the temporal distribution of rainfall events might change quite a bit, with less frequent but more intense rainfall events. This is potentially quite important for water-limited ecosystems, where plants may already be living in quite marginal conditions in terms of water stress.

In water-limited grassland ecosystems, it’s pretty well established that grass growth can be triggered by very short pulses of rainfall that only substantially wet the uppermost soil layers. What then about woody ecosystems, where the vegetation structure tends to be more complex? We’d like to know something about the relative impact of changes in rainfall distribution on plant productivity and respiration (including microbial soil respiration) and the net outcome in terms of ecosystem carbon fluxes.

We took a look at what happens by using data from the FLUXNET project, a worldwide network of flux towers measuring carbon fluxes and a whole bunch of associated data for long-term ecological and climate studies. The work mostly consisted of processing this data and trying to pick out the effects of variations in precipitation regimes in a systematic way. We found enough of an effect to get it published in Biogeosciences!

R. Wania, K. J. Meissner, M. Eby, V. K. Arora, I. Ross, A. J. Weaver (2012). Carbon-nitrogen feedbacks in the UVic ESCM. Geosci. Model Dev. 5, 1137-1160. PDF

This is the latest in a long series of collaborations with my partner Rita. For this one, my contributions were a weekend-long hacking session to get a first version of the nitrogen model that Rita wanted to use working and figuring out some of the details of how the vegetation model within the UVic ESCM really works. It was quite interesting, although we’re not completely convinced about the scientific merit of putting a detailed nitrogen model into a coarse-scale earth system model. But hey, it’s the fashion.

One thing that is very interesting to me is the disparity in work involved between a first author paper (often, full-time for months) and a second-or-subsidiary author paper (sometimes, not much more than a few discussion sessions with the principal authors). Out of ten papers in my publication list, only two are first author papers. That either shows that I play very nicely with others, or that I’m pathologically lazy and exploit other scientists to pad my publication list!

F. Gogé, R. Joffre, C. Jolivet, I. Ross, L. Ranjard (2012). Optimization criteria in sample selection step of local regression for quantitative analysis of large soil NIRS database. Chemometr. Intell. Lab. 110(1), 168-176.

This was another paper where my contribution was, I would like to think, limited in temporal extent, but pivotal in terms of scientific impact. (Heh.) One of the things I spent a lot of time thinking about during my PhD was dimensionality reduction methods. It turns out that these are used a lot in the spectral analysis of ecological samples (soils in this case), so I could offer a bit of advice to some coworkers at CEFE.

So, these three papers were more or less the entire output from an 18-month post-doc (I left before the two years were up). I had another manuscript that was quite interesting almost ready to go when I left, but I couldn’t really summon up the enthusiasm for a last push on that. It was another FLUXNET paper, this time about the relationship between global radiation (basically, sunshine) and net radiation (the balance of shortwave solar radiation and longwave thermal radiation) over different kinds of vegetation canopies. There are some interesting general relationships between these quantities that have been known since the 1960s or 70s, but no-one had done a really comprehensive comparative study of a lot of different sites of different ecosystem types. I don’t know if that stuff will ever get published, but the statistical models I built might be quite useful.

Apart from that, there was another abortive effort to use boosted regression trees to model fire occurrence in the Languedoc-Roussillon region. That failed because of a paucity of data, but a manuscript got to its second round of reviewing before I spotted a big mistake in the calculations that had made it look as though we could get some sort of decent results. So we had to withdraw that one.

Anyway, I think that might be my last desperate gasp for academic papers. If I do write any more in the future, I’m going to make sure that they are fun!