For their recent paper, 29 researchers came together to look at Geographic scale and disturbance influence intraspecific trait variability in leaves and roots of North American understory plants (Kumordzi, BB, Aubin, I, Cardou, F, et al. Funct Ecol. 2019; 00: 1– 14. https://doi.org/10.1111/1365-2435.13402)

In this Insight, Alison Munson talks about why they did it, what they learned and the challenges involved in bringing together multiple research teams for a continental-scale project.

What can we learn from this study?

This paper describes leaf and root trait ITV (intraspecific variability) of common boreal and temperate forest understory species, across a continental east-west gradient in Canada. We sampled ubiquitous, widespread boreal and temperate species found normally below the forest canopy, for which data are scarce despite their important presence in these forests, and their contribution to processes such as carbon and nitrogen cycles. We also included traits of fine roots, which have rarely been included in ITV studies; this permitted us to compare ITV above- and belowground.

We examined ITV at several scales, continental scale being the largest. This approach is also quite rare and logistically difficult, but lets us to understand the importance of ITV over the entire range of the six species studied (two shrubs, and four herb species). We sampled populations on sites affected by natural and anthropogenic disturbance, both very frequent in these commercial forests, which increases the width of the local gradient. In these forests, disturbance is an important driver of ecosystem structure and function. Thus, the study contributes to understanding the plastic responses of these common understory species in response to both continental-wide factors such as climate, or to changes in the local environment following disturbance.

How did you come up with this idea?

The idea for this study originated from a workshop on functional traits in Quebec, when we discussed the possibilities of a collaborative approach to accelerate data acquisition in huge areas such as Canada. Isabelle (Aubin) had launched the data bank TOPIC (Traits of Plants in Canada), and I was part of the scientific committee to work on encouraging Canadian researchers to send their trait data to this new national effort. A couple of years later we had funding from the Quebec research council (FRQNT) and from our original five-member team, we plotted about bringing together the forest and vegetation ecology community in Canada. We had seen from previous studies that ITV appeared to be quite important in boreal ecosystems (work by Kumordzi et al. 2015), and understory plants have been much less studied than the canopy species.

What was the biggest challenge for this work?

The challenge was to bring together a team of researchers across the country who already had field sites established for other studies in the boreal or temperate forest. We achieved this by sending out to colleagues a friendly open call for participation in a large collaborative study of ITV including the proposed six species. We were pleasantly surprised that the large majority of those contacted responded positively (23 teams in total). Then, we needed to draw up a detailed common protocol for sampling during a very short sampling window at the peak of the growing season. After many versions, we sent out the final protocol followed by pre-addressed, insulated courier boxes to send fresh root samples back to the two main laboratories that carried out measures of root traits using the same WinRhizo equipment. We had quite a team back in the labs, processing fresh and dried material as it arrived, an amazing intensive effort!

Bright Kumordzi arrived to do the quantitative analyses as a postdoc from Umea, where he had worked on ITV in boreal forest communities for his PhD. After his work on the data set, it was an important step to have a synthesis workshop (funded by CIEE, Canada’s synthesis centre) to bring most of the researchers to a meeting for two days, to discuss findings and work on the outlines for three prospective manuscripts to come out from our collaborative work. I am a great fan of synthesis meetings, mostly in out of the way places where we can continue to talk at meal times and into the evening. The group has been continually interested and eager to contribute with revisions and suggestions, in part because of our synthesis meeting. This has been an interesting community effort that will also bring more data into the data bank of Traits of Plants in Canada (TOPIC), one of our principal objectives.

Does this study goes beyond boreal forests?

We found that locally sampling these species in undisturbed and disturbed environments captured a large proportion of the intraspecific variability, for all species. This has practical implications for sampling ITV at different scales. However, another proportion of variability could not be explained at the scales measured, indicating that it is also important to measure ITV at the level of individuals, and perhaps within individual organs such as fine roots. These data are useful to understand plasticity of these plants under changing environments, and can potentially be integrated into modelling of their response to global change. The effort to improve above and belowground process models or DGVMs including understory plants is the focus of a future synthesis group in Canada.

What are the next steps in your research?

A subsequent manuscript examines the drivers of ITV at different scales. We also probed the genetic variability of one of the species across its entire range, in relation to measured trait variability, with some surprises! This work is also being finalized for submission. Our results point to the need to examine ITV at smaller scales, and some preliminary work is in progress in this orientation. It will be important to better characterize where ITV will be important versus interspecific variation. This has been a very enriching study for all involved, and helps us seeing forward how collaborative research at this scale can certainly work well!

Read the paper in full here or the free plain language summary here.