In this post Xavier Morin, Researcher at CEFE, CNRS, University of Montpellier, presents novel perspectives on forest gap models, highlights the complexity of ecological systems and remembers the path that lead him to being a forest scientist.
About the paper
Forest gap models, the first of which were developed almost 50 years ago, simulate forest dynamics (tree recruitment, growth and death) according to biotic interactions (especially competition for light) and, for most of them, abiotic drivers such as climate. In this paper, we targeted two aims. First we have validated a forest gap model in a “classic” way, which is to show that it can reproduce observed or expected vegetation patterns or community composition in the long term. We showed the model reliability for most climatic conditions in France. Second, we have also shown that such a model can also predict forest productivity across a few years, ie. ‘short term functioning’, with strong accuracy. We further highlight that such a finding was consistent for both monospecific and mixed stands.
Interestingly, the idea for carrying out this study partly came from an observation about previous studies. Indeed I had used gap models to test for the strength of the relationship between tree species richness and productivity, thus relying on the comparison of simulations of monospecific and mixed stands. However, the accuracy of gap models prediction in monospecific stands had been very rarely assessed. Thus came the idea of validating this kind of models for mixed stands but also for monospecific stands.
The novelty of this study also lies in the dual ability of such models to predict species composition in the long term as well as ecosystem functioning in the short term. We thus believe that using this kind of model that presents a balance between generality (ie. relatively simple to parameterize) and realism (i.e., predicting accuracy), may open great perspectives, especially to explore of how tree species richness in forests affects stand productivity, and how climate change will impact these patterns at both short and long term.
About the research
In ecology in general and in forest ecology in particular, there are a wide range of models, with various levels of complexity. Of course this complexity should fit with the question to be answered. For instance I valuate the development of detailed process-based models to increase the robustness of the predictions, which is notably key in a context of strong on going environmental changes. Yet I personally advocate the principle of parsimony, seeking to ‘explain the more with the less’.
But model simulations are meaningful when grounded with observations in the field. In my research I thus try to keep a balance between these two aspects, and I really enjoy to carry out studies with one approach or the other.
How did you get into ecology?
I just like forests. I think I was first fascinated by the ambiance and the diversity of these ecosystems. In France we have the chance to have many different forests in a short range : lowland deciduous forests, alpine forests, Mediterranean evergreen forests… But of course this feeling strengthened when I had the opportunity to discover forest ecosystems all around the world (remembering the majestic redwoods of Vancouver Island or Nothofagus forests of Patagonia). Then, trained as a forest engineer, I realized how complex these ecosystems can be, but how fun it can be to study them! Thus I did not hesitate when I had the chance to do a PhD in forest ecology and post docs in Canada and Switzerland, about tree species distribution, phenology, forest dynamics and climate change impacts. These latter became the second reason why I dived even more in forest ecology. The climate emergency and the pressure it imposes on forests – through direct impacts on trees and associated species but also because forests are considered as key levers for mitigation – actually strengthened the responsibility to my research efforts.
One piece of advice for someone in your field…
Don’t be afraid to communicate about your research! Because, more than ever, we need competent people to talk about ecological issues. And enjoy your work: ecology is important of course, but it is also fun!