In this blog post, Associate Editor Hans Cornelissen writes about the impact his teaching has had on the development of his research and publications over the years…

Autumn is always a very busy teaching season for me – my poor excuse for being slow with my editorial activities for this journal (including writing this blog)… yes, I do tend to feel guilty for much of autumn.

Recently, I taught a 4 week MSc Ecology course on ‘Soil-Plant-Animal Interactions’ and currently I am teaching both a 2^nd year undergraduate course on Ecosystem Services (to geographers) and a 1^st-year undergraduate biology course on the ‘Evolution and Diversity of Life’ in which I cover the evolution of plants and fungi – not that I know much about fungi but I do know how to get the best out of mushrooms in a pasta.

It is the latter course in particular that made me think about how my teaching activities over the years relate to Journal of Ecology in a positive sense, i.e. other than teaching getting in the way of journal editing time. When I sit back for a moment to think about this, there are many examples of how interactions with my students, whether in the lecture hall, the lab or  the field, have inspired or triggered me to start new research lines, some of which have eventually made it into the ‘good literature’. For instance, my relatively recent research line on plant trait effects on flammability has benefitted greatly from small pilot experiments done by master’s students during the above MSc course. One group of students developed a nice methodology to measure how fire and its associated high temperatures can (or cannot) be conducted via bark of different tree species – not unimportant for understanding trees’ tolerances of fire and for potential exchanges between surface and crown fires.

The particular example that I want to highlight here is different in the sense that it relates to the above-mentioned 1^st-year evolutionary course, where the somewhat one-directional transfer of knowledge still dominates and the students do much practical work but not their own research project. And another point about this example is that it relates rather directly to Journal of Ecology… (building up the excitement here before giving the telling details below).

Next week I’ll be lecturing again about the different eras in the geological history, with their climatic and atmospheric peculiarities, and how these relate to the major plant clades that dominated those eras. I always get excited when I can lecture about the tree ferns, giant lycopods and horsetails of the carboniferous period, and show students fossil evidence of them as well as modern descendants in the botanical garden of Amsterdam, Hortus Botanicus.

I also teach about the amazing diversity of gymnosperms (‘conifers’) which coexisted with dinosaurs during the Mesozoic, from the ginkgos with their superb fan-shaped yellow-orange autumn leaves, to fat 300-year old cycad palms in giant wooden plant pots (which the Dutch stole from South Africa when that was still considered to be okay), and to weird monkey puzzle trees (Araucaria).

I believe what started off a new research line about five years ago, was a practical in the Hortus Botanicus, where the students and I admired and touched the super-tough leaves of the cycads and monkey puzzles and got hurt by the absolutely vicious spiny extensions of those tough leaves. Obviously this then always leads to a discussion about which animals these plants are (still) defended against; and then to the co-evolution of dinosaurs and the ancestors of these gymnosperms trees. During one of these sessions of group masochism, it suddenly clicked: these tough, spiny anti-dino defences must have had legacy effects on the traits of the leaves after death. In other words, leaves that were and still are (in ‘living fossils’) well defended against herbivorous dinosaurs, should turn into litter that is very slow to decompose.

Over the years I have enjoyed much vivid discussion and collaboration about evolutionary ecology with old friend and partner in crime Will Cornwell (also a Journal of Ecology Associate Editor). Together with Will, we decided to test  many different gymnosperm clades, and reference angiosperm clades, for their potential decomposition rates, using the litter bed method for simultaneous multispecies comparison of decomposability that was introduced in this journal 20 years ago (Cornelissen 1996, J. Ecol.). While this gymnosperm work is still in the pipeline (please, J. Ecol., reserve some space for it) related research activities that Will and I have undertaken with Guofang Liu and other Chinese colleagues have been published in this journal.

Will Cornwell and Hans Cornelissen collecting basal angiosperm litter in Xishuangbanna Tropical Botanical Garden, Southern China

In 2014 we organised the Special Feature on ‘The Tree of Life in ecosystems: evolution of plant effects on carbon and nutrient cycling’. Our own specific contribution to this special feature, besides an editorial (Cornelissen and Cornwell 2014, J. Ecol.), is a paper about a litter bed experiment we carried out in Xishuangbanna Tropical Botanical Garden in Southern China (Liu et al. 2014, J. Ecol.). The theory around this work is closely related to the gymnosperm project and also has a close link both to Will and to the same 1^st-year course; I also teach every year about the evolution of different clades of angiosperms (flowering plants). Basal angiosperms such as laurels, magnolias and water lilies are evolutionarily older than eudicots, which now host most of the modern dicot taxa. Because leaves of basal angiosperms were considered to be more ‘primitive’, for instance in their vein proliferation pattern, and therefore presumably tougher, we hypothesised that they should also be more recalcitrant to decomposers and thus decompose and release carbon relatively slowly.

Guofang Liu collecting dead wood of a giant bamboo at Xishuangbanna Tropical Botanical Garden, 2012

We put this to the test by comparing leaf litter of over a hundred basal angiosperm and eudicot species for decomposability (via mass loss rates) in litterbags in a tropical ’common garden’ litter bed.  Low and behold, basal angiosperms indeed were generally less decomposable than eudicots. We think this information helps us to understand the role of vegetation composition in carbon cycling since the start of dominance of angiosperms on Earth (i.e. meteorite attack at the end of the Cretaceous had caused drastic global environmental change).

Collections of basal angiosperm and eudicot litter for use in litterbags in the tropical litter bed

Another important evolutionary angiosperm group I tell my students about every year is the monocots and especially bamboos, which essentially are woody grasses. I show them in slides how the 20 cm diameter culms of Phyllostachys pubescens from SW China are applied as scaffolding and yokes for carrying stones around and let the students feel how hard and tough these stems are.

And, now, after another major operation of litter collecting, processing and measurement by roughly the same East-West team, we know that the wood of bamboos is generally decomposed more slowly than the wood of eudicot trees of the same diameter (Liu et al. 2015, J. Ecol.). These findings not only tell us about trait evolution and carbon cycling, but also add to the growing interest in bamboos for climate warming control as it seems that bamboos can sequester carbon fast by having productive leaves, while the recalcitrant wood (together with the major rhizome networks) helps to retain this carbon in the system rather than seeing it released back to atmosphere.

One of the tropical litterbed blocks for comparing wood decomposability of many bamboo and eudicot species, 2012

Of course, teaching about the evolution of plants has not been the only factor leading to the ideas that underlie the above papers in Journal of Ecology; that would not do enough justice to the input of the nice scientist friends I work with.  But I am convinced that discussing their evolutionary context and observing and touching these plants with the students every year, played a critical role in developing this new and exciting research line.

Scholars like me often complain that we have to do so much teaching while we are assessed mostly for our papers and citations. But the above is only one example that teaching is not only a matter of giving, it helps us to learn about or refresh important topics that are not directly linked to our research right now, but which one day will allow us to make that new link, perhaps even a breakthrough that we would never have hit upon without being surrounded by curious students. Simply discussing or visualising certain organisms or evolutionary and ecological topics to and with the students may suddenly trigger something new and exciting that five years later may inform scholars around the world via a paper in Journal of Ecology or another journal. This week I’ll show my students the fossilized stem scars of what used to be 60 m tall lycopod trees. Who knows what exciting new stuff you will read about the role of plants in the carbon cycle during the Carboniferous in this journal in 2021…

Hans Cornelissen, Associate Editor
Vrije Universiteit Amsterdam