Our newest paper from our common garden experiment testing whether plant-induced soil heterogeneity promotes plant species coexistence is out in the April issue of Oecologia. In this paper we show that soil heterogeneity increases per capita biomass of invaders (i.e. the disadvantaged species in a competing pair). By using a reciprocal invasion among species pairs in our experimental design, this indicates mutual invasibility by this species pair, which is a criterion for stable coexistence. Moreover, we unlock the “black box” of mechanistic drivers of plant-soil feedbacks by measuring the spatial arrangement in both biotic and abiotic soil properties within our experimentally-created soil treatments. We show that soil biota (bacteria and fungi) and phosphorous may be important drivers of the reproductive biomass response to the spatial arrangement of plant-soil feedbacks.
This paper wouldn’t have been possible without the outstanding work of Ph.D. student, Jennifer Murphy, and undergraduate student, Angela Kaczowka, along with many other students of the Burns lab who assisted with experimental set-up and data collection over the 4 years of the experiment.
I’ve recently had the opportunity to expand my academic horizons by assisting a Ph.D. student (who has now completed his degree!) with statistical analysis of morphological data from two purported species of New Zealand brachiopods, which are shelled marine animals in their own phylum that is closely related to the molluscs. Though we were unable to statistically distinguish the species based on morphometrics, enzyme analysis indicated that they should remain separated. Moreover, we confirmed that morphological differences between brachiopod species in other genera range from very small to quite large. It’s been quite a novel experience for this plant community ecologist to have a hand in taxonomic research, and on marine animals at that!
After a busy couple of months doing final revisions and checking proofs for two manuscripts co-authored with stellar undergraduates from the Burns Lab at CWRU, I was happy to find that both manuscripts went online yesterday!
First, in an experiment that manipulated the timing of plant establishment in competition between congeners, we found evidence for plasticity in two functional traits that is consistent with predictions for adaptive trait plasticity in some species, where the later-establishing plant’s trait values would maximize resource capture. The type of plastic response — either a difference between late- vs. early-establishing plants of the same species or divergence in trait values between potmates — differed by genus. Moreover, divergence in specific leaf area between potmates positively correlated with combined biomass of those potmates, consistent with putatively adaptive trait plasticity. This work, co-authored with Conor Leahy and Nicole Zimmerman as well as Dr. Jean Burns, is now published in Oecologia. Nicole has now completed a Master’s degree in biostatistics from the University of Michigan and I especially appreciated her help with the statistical analysis in this paper.
Second, in a paper led by Gaston del Pino and now published in Plant Ecology, we show evidence for functional trait plasticity in response to experimentally-manipulated heterogeneity in both the above- and belowground environment (light and soil heterogeneity, respectively). We found that above- and belowground heterogeneity can interact to affect trait expression. We also found non-additive effects of mixing soils of two origins (i.e. collected from the zone of root influence of different plant species in the field), which is consistent with findings in my previous work with Dr. Burns (here and here).
Our methods paper in the Journal of Visualized Experiments is now available online, complete with video demonstrating our protocol for producing heterogeneous and homogenous soil treatments in the context of plant-soil feedbacks. I helped develop this technique during my post-doc in the Burns Lab at CWRU and we’ve used it both to document recruitment effects of soil heterogeneity (Brandt et al. 2013) and to demonstrate how soil heterogeneity affects mutual invasibility (Burns and Brandt, in press).