Jana Doudová: Under the dominants

Jana Doudová, research at the Czech University of Life Sciences in Prague, explains his work ‘Along with intraspecific functional trait variation, individual performance is key to resolving community assembly processes’, highlights how plant facilitation can be present in productive ecosystems and tells her history about how she got fascinated by plants. 

Wetland team collecting data in the filed with Jana in the middle
Wetland team collecting data in the filed with Jana in the middle

About the paper

What’s your paper about?

Garden experiment and biomass collecting, summer 2015
Garden experiment and biomass collecting, summer 2015

Some earlier studies have shown that large species need not operate always as competitors, but under some circumstances they may serve as nurse plants, helping to ensure biomass stability of subordinate species. This has been observed exclusively under stressed conditions. Most studies have documented this phenomenon in relatively harsh ecosystems such as in arid and semiarid areas or in alpine plant communities, where water and nutrients are particularly limiting. Here, we extend this model to cover wetland plant communities that lie at the opposite extreme of the water and productivity gradient. Our results thus show that non-dominant subordinate species may be facilitated by dominant species also in ecosystems where highly asymmetric competition for light is to be expected.

What is the background behind your paper?

I have been studying temperate swamp forests and processes which determine plant diversity of this specific type of environment for a long time. My husband and me have long been fascinated by alder carrs, forests dominated by Alnus glutinosa that are rare in Central Europe. The environment is highly heterogeneous here and is composed by hummocks and hollows, which create strong moister gradients at small scales within the community. This is an amazing system for studying processes determining species coexistence directly in the field. Motivated by this consideration, we first tested “habitat heterogeneity hypothesis” by recording vascular species along selected environmental gradients in the field. In 2012 we published our first paper on species coexistence mechanisms. Here, we found that local heterogeneity in microtopography and light availability were significantly correlated with a great diversity of bryophytes and woody plant species. The distribution of herbaceous species was, however, left unexplained. Curious to identify the processes behind the distribution of herbaceous species prompted us to establish a 5-year-long garden experiment, which has provided us with a greater insight into the community processes. Four species typical of swamps forests were selected for the experiment, one dominant and three subordinate. The principal question the experiment strove to answer was how the dominant species affected less competitive subordinate species under various water level regimes, such as water optimal regime, inter-annual drought and permanent drought. The experiment has led to two papers:  the first published in 2018 showed that dominant species increases temporal stability of subordinate species under different regimes of drought stress, although there are different mechanisms at play here. While species asynchrony is the likely mechanism connected with inter-annual drought, under permanent drought the changes in plant interactions to less competitive and facilitative increased temporal stability measured by year on year ramet dynamics. Detailed measurements of individuals’ fitness and of plant responses to water stress, using functional traits, have revealed more detailed mechanisms of species coexistence. The results are summarized in this paper. We found that dominant species supressed drought-tolerant species with low competitive ability, and supported less drought-tolerant species with relatively high competitive ability under the permanent drought stress. At the same time, we supported the idea that neutral processes play important roles in maintaining species coexistence in wetlands.

How did you come up with the idea for it?

After we published our field study, we realized that we would not be able to identify the subtle plant-plant interactions without conducting an experiment. 

What are the key messages of your article?

Black alder (Alnus glutinosa) swamp forest; The nature reserve Vrbenské Ponds near Budweis in South Bohemia
Black alder (Alnus glutinosa) swamp forest; The nature reserve Vrbenské Ponds near Budweis in South Bohemia

Our results show that wetland communities are resistant to prolonged drought periods and able to survive them for a certain time without this having a major impact on their diversity. In wetlands, drought periods are a common feature of hydrological regimes, even in natural systems unaffected by human activity. Our results indicate that environmental fluctuations lead to higher temporal stability and maintain diversity of subordinate species in wetland communities. From the methodological point of view, it points out how important it is to relate individual trait variation to individual variation in plant fitness proxies, when studying community processes.

Who should read your paper (people that work in a particular field, policy makers, etc.)?

Everyone who is interested in community-level processes.

Alder carr community with a dominant species Carex elata (at the back) and threatened species Calla palustris (in the front)
Alder carr community with a dominant species Carex elata (at the back) and threatened species Calla palustris (in the front)

About the Author

How did you get involved in ecology?

This goes back to my master thesis, after which I focused my doctoral research on the phenotypic plasticity of a chenopod weed (Atriplex tatarica), which has been spreading around Europe due to the changing climate. Gradually, however, I became increasingly captivated by plant communities and processes that govern species coexistence and began working with my husband, who has been a great motivation for me. While I really enjoy working in the field , from the scientific point of view I am even more fascinated by designing experiments, as I am convinced that only well-established experiments can yield credible evidence and identify processes within plant communities.   

What are you currently working on?

We have a small team focused on vegetation ecology and plant biodiversity protection of the European lowland forests. Our aim is to understand temporal vegetation changes related to ongoing environmental change and identify plant assembly processes standing behind them. Ten years ago, we started two long-term experiments in forest communities at the opposite points of moisture gradient (swamp and thermophilous forest). Currently, these experiments represent rare cases of long-term survey in European temperate deciduous forests. We are also highly interested in management application for biodiversity protection. In this context we have experimentally tested effects of reintroduction of selected traditional forest practices (litter raking and grass cutting) on the diversity of plant community in thermophilous oak forest (see our paper) and this year we managed to set up new monitoring plots for testing the effects of coppicing. Our team is open to newcomers interested in community processes and biodiversity protection of forest vegetation.

Read the paper in full here.

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