In this new post Rutger Wilschut and Hanna Ruppert from University of Wageningen present their work ‘Contrasting responses of naturalized alien and native plants to native soil biota and drought’. Here they discuss how origin has important implications for biotic interactions, show the key role of soil biota for plants, and share their experiences which led them to pursue lives as ecologists.
About the paper (Rutger)
Decades of research on non-native plant invasions have shown the importance of interactions between non-native plants and native soil biota for non-native plant success. Outside of their native range, non-native plants associate with different soil biotic communities than in their native range. These often do not contain co-evolved plant pathogens, but do contain plant-mutualists, such as arbuscular mycorrhizal fungi, with which non-native plants can readily interact. Consequently, non-native plants – at least, the ones that successfully established outside of their native range – often suffer less from interactions with native soil communities than native plants do, and therefore may exert a strong competitive impact on native plants. At the same time, plant communities are exposed to climate warming and an increase in extreme weather events. Predicting how non-native plants will ultimately affect native plant communities therefore requires an understanding of the impacts of climate change on native and non-native plant performance, which is what our paper is about.
As a postdoctoral researcher in the group of Prof. Mark van Kleunen at the University of Konstanz, I was inspired to establish new research lines in invasion ecology, alongside my main research on plant-soil feedbacks. Having seen the impacts of long-lasting summer droughts on plant communities in recent years, I became interested in the question: how do droughts modify soil community impacts on native and non-native plant performance? Working together with other students is a great way to explore new research avenues, and I therefore proposed this topic for a possible BSc-thesis in our group. I was very lucky to be approached by Hannah Ruppert, who was interested in the topic, and in plant-fungal interactions in particular. Together, we developed the definitive set-up of a greenhouse pot experiment, in which Hannah examined the responses of native and non-native plants, growing alone or in interspecific competition, to the interactive effects of native soil community presence and drought. The project proved to work out wonderfully, a large part of which was due to Hannah’s dedication to get the most out of the experiment.
In our project, we particularly wanted to test whether droughts, through anticipated negative effects on soil pathogens, would neutralize differences in soil biotic effects on native and non-native plant performance. Our study, however, showed that native plants indeed benefitted less from soil communities than non-native plants, but that drought did not alter this pattern. Interestingly, drought directly affected non-native plants more negatively than native plants, which may be explained by the more acquisitive growth strategy of successful non-native plants. As such, our study suggests that drought may weaken the competitive benefits of non-native plants over native plants through direct-, but not through indirect effects.
About the research (Hannah)
What was really beautiful about carrying out this study (apart from spending a lot of time working with plants and soil), was that you could already visibly see the effects of the treatments during the experiment. Our experiment took place in the greenhouses of the botanical garden of the University of Konstanz. It is relatively obvious that the drought treatment would be observable, but I did not expect the soil community treatment to be so clearly visible. Already in the first few weeks the drought and soil biota treatments showed clear differences: as expected the drought treated plants grew way smaller than the ones being well-watered, but there was also a visible difference between the sterilized and live soil: plants grew faster and bigger when having the native soil community which was really exciting to me. Additionally, most non-native plants were growing visibly faster with the soil community present than native plants, which was then also confirmed by our statistical analysis. Initially, we thought the soil community would overall be more harmful to plants, and that non-native plants would be less harmed since they were released from their home pathogens and that this benefit over native plants would be less pronounced under drought since the soil community would be less active. However, the majority of our plants reacted differently than expected and were thriving with the soil community regardless of the drought treatment.
So we got curious: are arbuscular mycorrhizal fungi (AMF) perhaps responsible for the increased growth within the soil community treatment? And were the non-native plants eventually more colonized by AMF than the natives? To address these questions, we decided to stain the roots for examining AMF colonization. The plants grown with the soil community were clearly colonized by AMF but we did not find any significant differences between native and non-native origin or drought treatment. AMF colonization rates are not necessarily directly connected to the benefit they convey to plants, but in our study, AMF colonization cor to the effect of our soil biotic treatment on plant performance. Therefore, our observations do tell that AMF probably contributed to an increased plant growth.
About the authors
Hannah: I was really excited and felt honored to be able to do my BSc. Project in the Plant Ecology group of Prof. van Kleunen and to be given the responsibility to lead the greenhouse experiment. During my Biology studies I enjoyed microbiology the most and was so excited about discovering the hidden world of tiny organisms in the soil, omnipresent but not visible. Therefore, I was really excited to be part of a project investigating how a soil community affects plants of different origins when exposed to drought. I also was surprised and shocked how little we know about the large diversity of microorganisms belowground, even though they have so much importance in our terrestrial ecosystems. This lead me to pursue a research master in Ecology in which I focused on mycorrhizal fungi because to me the symbiosis between plants and fungi doesn’t stop to excite me. It fascinates me how we can’t see their extensive fungal network in the soil, but how mycorrhizal fungi affect so many processes aboveground, from plant performance to carbon and general nutrient cycling and so many more processes. Just as in our society, there are so many processes from unknown actors not visible to us, but essential for our survival.
Rutger: I developed a strong interest in natural history and biodiversity already well before going to university, and spend a large part of my free time roaming about nature in search of nice birds and plants. Spending a lot of time in nature makes you realize how quickly the composition of ecological communities is changing, which is both intriguing and scary. During my BSc and MSc studies at Wageningen University (The Netherlands), I was inspired by courses on plant systematics, phylogenetics and biogeography, and I likely would have tried to pursue a PhD in this direction if it wasn’t for a guest lecture by Prof. Wim van der Putten, during one of my last MSc courses, in which he which spoke about the role of soil biota in the success of climate-change driven range-expanding plant species. My MSc-thesis in his group at the Netherlands Institute of Ecology (on a completely different topic, actually) convinced me that experimental ecology suited me much better than the more database- and lab work-focused research in evolutionary ecology and phylogenetics – I simply feel a bit more comfortable working in a greenhouse than in a molecular lab! I got very lucky that PhD-positions opened up in the group of Wim right when I was about to finish my MSc, and soon after I found myself diving into the world of plant-soil interactions and global change ecology. My PhD-project was specifically focused on interactions between range-expanding plant species and nematode communities, but I widened my research to also include experimental projects on feedback interactions between plants and complete soil communities. I continued this plant-soil feedback research during my first postdoc, for which I moved to Konstanz (Germany), and during my second postdoc (back at Wageningen University), but I am nowadays studying these interactions from a plant community perspective. Overall, my aim is to improve our understanding of how interactions that plants develop with communities of above- and belowground organisms depend on the plant community context.
Life as a scientist has given me a lot of freedom, but at times has its challenges. As I (during my early studies) could not really imagine living outside of the Netherlands for an extended period, it was quite a big step to move abroad for a postdoc position, but I’m very happy I did. An important realization was that living abroad (even in a neighboring country) helped me to reflect on the things that I like about (living in) my home country, which I appreciated more since I moved back. Since then, I of course also found out about downsides of my home country (it’s much, much harder to find a quiet nature area in the Netherlands than in Germany, for example!). Despite this, I did not necessarily intend to move abroad again, but in 2025 I will nevertheless very likely leave the Netherlands another time for a new position. Let’s see what the future brings – I’m sure it will involve more interesting experimental research, as well as nice nature areas to explore!
Like the blog post? Read the research article here.
