In this new post, Eva Janíková—a postdoc at the University of South Bohemia (Czech Republic)—presents her latest work: ‘Methods of species pool determination as predictors of survival in seeding and transplanting experiments’. She discusses the mechanisms behind species community composition, highlights the complexity of ecological research, and shares how working in ecology is the perfect match for her love for nature.
About the paper
When you walk through the countryside, you can see many types of different habitats. When you focus on one habitat type, for example meadows, you can see so many differences between individual sites. Meadows can be dry or wet, species rich or very species poor, and productive or unproductive with regards to biomass. There are so many factors which determine species community composition. However, which factors are the most important and how can we differentiate the effect of these individual factors? If a species is absent from a locality, does that mean that the site conditions are inappropriate for accommodating it?
Plant community composition is limited firstly by a species’ ability to reach the site. The establishment and survival are further constrained by both abiotic conditions and biotic interactions operating together on local scales. In this paper, we focused on these two filtering mechanisms which importantly influence not only species composition of meadows, but also the results of many studies comparing realized plant species composition within a species pool. We did this in order to reveal the many drivers of ecological processes. For this reason, it is very important to clearly define the species pool, against which community composition is compared.
Most studies use the species pool, which includes species’ ability to survive both abiotic and biotic constraints of the locality/localities, to assess community composition. Nevertheless, if we want to study the effects of individual factors on species community composition—including biotic interactions—we are not able to distinguish the effects of biotic and abiotic filters using this type of species pool. Most methods of species pool determination are based on the realized niches of species and thus exclude from the species pool all species which cannot withstand the competitive pressure of other species, even if they are able to survive in the abiotic conditions of a given locality. Thus, these estimation methods a priori underestimate the effects of biotic filters.
We tried to compare the effectiveness of different methods of species pool determination with the results of an experimental approach. This approach involved adding both resident and non-resident species—with very ecologically different requirements—to four localities on a moisture gradient, both into competition-free gaps and into intact vegetation. We used plants at different life stages to compare the effects of different factors on germinating seeds, small seedlings, and established individuals. Although this experimental approach is very time-consuming and has its own limitations, there is no other method which can conclusively distinguish the effects of biotic and abiotic filters. All researchers using comparative methods of species pool determination should ensure that they use appropriate species pools.
About the research
Our research focuses mainly on an experimental approach which clarifies many ecological mechanisms and processes. Without these experiments, it is not possible to properly differentiate the importance of the abiotic and biotic effects on species community composition, or determine habitat suitability of a target species. Nevertheless, because the experimental approach is quite demanding and time-consuming, data modelling and observations became a faster and often easier way to get satisfactory (albeit incomplete) information. It is worth mentioning that permanent plots—with manipulation of the target community and long-term perspectives—can bring more valuable and interesting results.
We realized that results from this experimental approach are importantly distinguished from approaches which use estimation methods of species pool-determination—these are based mainly on observations and not manipulations. It was surprising how many species—with very different habitat preferences relative to the target locality—were able to survive under specific abiotic conditions of the site, but couldn’t withstand the competitive pressures of the surrounding vegetation. These species are normally excluded from the habitat species pool by estimation methods because these methods are not able to distinguish between abiotic and biotic filters. Biotic filters are therefore very underestimated in many studies—competition seems to be one of the most important drivers of species community composition, especially in the establishment phase of species. It is also very important to consider the entire life cycle of a species when studying species establishment in a community. To assist this, we recommend using individuals at different life stages, just as we did in our study. This enabled us to compare the importance of regeneration and realized niches for community filtering.
Many unanswered questions remain about the role of aboveground and belowground competition. It is evident that competition plays a very important role in species community composition. Nevertheless, many researchers focus only on aboveground competition, which is asymmetric, while more symmetric belowground competition is lightly studied. Thus, there remains a big question: which type of competition has a greater effect on plant community composition?
About the author
I love walking, cycling, camping, and purely and simply being in nature. It’s not just that nature is lovely and one can be at peace and gather strength, but also because it is frankly just very interesting! It is fascinating to take note of and appreciate the many things that happen around us without our intervention. I take a lot of pleasure from observing and spending time in the mysteries of nature, and for that, it is necessary to go out, look around, and keep your eyes and mind open.
I grew up in a small village in a house with a big garden. I spent a lot of time wandering in nature, firstly around my home, then in my country, and finally by travelling abroad. In all my travels, whether it was with my family, scouts, or with other friends, I have always tried to be as close to nature as possible. This is what drove me to study biology as it represented a way to further understand and appreciate nature. I chose botany as my field and focused on the community ecology of plants at the University of South Bohemia in České Budějovice where I finished my Ph.D. I am currently working there as a postdoc, and I’m enjoying collaborations with many great people from Jan Lepš’s working group of functional ecology!
I believe that the most important thing for any ecologist is to get out in nature, not just because of work but also for relaxation—just let the thoughts flow! This is such a great source of inspiration which can then go on to form the foundations of new projects and work!
Enjoyed the blogpost? Read the research here!
