Emil Nordström (former Master student), together with Lutz Eckstein and Lovisa Lind published a paper studying decomposition along the bog-forest edge (also known as “lagg”) using the tea-bag-index.

This paper, which was based on Emil Nordström’s Master thesis, is published in the journal Ecosphere (https://doi.org/10.1002/ecs2.4234). The authors studied the mass losses (90 days) of green and rooibos tea bags placed across the bog-forest transition of six bogs in Dalarna (Sweden). Three 20-m transects, each containing seven pairs of tea bags, were buried across the margins of each bog, centered at the edge of the Sphagnum moss (Figure 1). The results confirmed their hypothesis, showing a strong edge effect across the bog-forest transition (Figure 2).

Figure 1. Placement of tea bag pairs relative to the bog edge, where 0 m indicates the edge between bog and forest
Figure 2. Interaction between where tea bags were placed relative to the edge of the bog, with the -10 position furthest out into the bog, and their resulting (a) stabilization factor (S) and (b) decomposition rate (k) values. The shaded area represents 95% CI of the line fit.

Soil moisture levels had the strongest negative effects on decomposition rates. In comparison to soil moisture, pH and temperature had minor or no significant effects. Plants indicative of low decomposition rates included Vaccinium oxycoccos, Drosera rotundifolia, and Sphagnum species. In contrast to other studies, the authors did not find an increase in decomposition with increased species richness among the studied bog ecosystems.

In conclusion, there is an edge effect on decomposition and maintaining or restoring the hydrology of a peatland is the most important factor for continued carbon storage. A rough estimation of an areas’ decomposition rate appears to be possible based on its vegetation.

The Scanian river Vramsån (Fig 1) has been a stage for RivEM research before, but not with the wide range of methods that Ph.D. candidate Sebastian, visiting intern Hanna Paikert and Ph.D. candidate Jacqueline tried out in May this year!

Vramsån has long been used for hydropower purposes but is now in the process of being restored to a more natural flow regime. It is one of seven rivers of interest to the LIFE Connects conservation project, which aims to improve their ecosystem functions and ecosystem services. Under six years the project will work with removal of hydropower plants and dams, create fauna passages and improve migration paths at barriers. The project also works on innovative passage solutions that enables both hydropower production and fish migration as well as riverbed restorations to gain more natural habitats and improved water quality. The goal is to improve survival and production of threatened fish species such as Atlantic salmon and European eel as well as the endangered mussel species Freshwater pearl mussel and Thick-shelled river mussel. Research and information efforts linked to river restorations within the project will constitute an important part of the project, that you can read more about on https://lifeconnects.se/!

With that in mind, the first goal of this research adventure was to collect fish and mussel specimens for a study on the impact of light pollution on the host-parasite relationship of the endangered Thick-shelled river mussel (Unio crassus) and its host the common Eurasian minnow (Phoxinus phoxinus).  

This incredibly endangered, and ecologically significant mussel has rapidly diminishing populations, something that LIFE Connects is trying to change. While many people don’t think much of these simple bivalves they play a key role in keeping environmental conditions stable. By filtering suspended particulates from the water column large populations of mussels can keep water cleaner, a benefit to both fish and humans. When they need to poop, the majority goes into the surrounding sediment, fertilizing it and improving both benthic fauna communities and plant growth. Together, these help fortify fish and bird populations. Not only does the increased plant growth provide habitat but the increase in benthic fauna provides more food sources as a large part of benthic fauna communities are comprised of the larval forms of terrestrial insects.

One of the main ways we try to prevent the Thick-shelled river mussel from going extinct is to increase the chances of their reproductive success, a complex cycle and significant factor in their population decline. These mussels are partial parasites on fish, with this extra step making their reproduction rate be quite a bit slower than other freshwater bivalves. We can help by forcefully infecting host fish with mussel larvae and keeping them safe for a large part of the reproductive cycle before releasing them back into the wild. As such the first part of this study was to go electrofishing for fish to use as hosts in for the mussels to be reintroduced, primarily minnows and trout. The trout got to stay in the river (Fig 2) while the minnows were destined to come back to KAU to be used in some experiments. More on that in another blog post

Re-naturalizing the flow regime of a river doesn’t just affect the fish and their ecological functions in it, but other processes as well. Dispersal is one of these processes, and is thought to be important for the composition of all plant communities, including those that we find in-water and in the riparian zone. There are many ways in which plants disperse (Fig 3), and a large part of Jacqueline’s Ph.D. project focuses on dispersal via water. Most of this dispersal is in the direction of the water flow, but many people overlook a tiny component: the animals in the water that swim in the opposite direction! These animals can carry seeds on their outsides or, via foraging, in their bodies. This relatively little-studied function called endozoochory builds on the thought that animals spread other species by eating them in one place and pooping them out elsewhere.

A second goal of this week was finding out whether this pathway is an important route for riparian vegetation in Vramsån. The fish that we were catching thus had a double function: not only will they be used for mussel larva infestation, but we collected their poop to compare the seeds therein with seeds and vegetation in other parts of the ecosystem (Fig 4).

Which other parts, you ask? Well, of course, fish stomachs are not the only place where you find seeds – far from that! Given that there are so many ways in which plants disperse, we planned a comparison of the seed composition in different parts of the ecosystem. So, equipped with self-built traps to filter seeds from the water (Fig. a), to catch seeds from the air (Fig. b) and loads of boxes to sample riparian litter, riparian soil and aquatic soil, we went to work!

It took some hours to get everything in place, but while Seb will spend his spring infesting his fish in Karlstad University’s (KAUs) aquarium facility, Hanna and Jacqueline are running a germination study to see which species pop up in the samples of the different ecosystem parts. After two weeks in KAUs plant growing room, over 200 seeds of at least 10 different species have germinated across the different sample types. We are giving the samples a few more weeks to see what else poops up before we’re going to try and sniff out if there’s anything interesting in there!

Road verges act as important refuges for grassland species since the areas of semi-natural grassland have declined during the last century. However, as linear habitats, road verges increase connectivity in fragmented landscapes, which also makes them prone to colonization by non-native species. This is currently seen as the greatest threat to species-rich road verges. The invasive Garden Lupine is commonly found in road verges where it alters competitive interactions, reduces native populations, and even causes extinctions of native species. 

This project is funded by The Swedish Transport Administration (Trafikverket) and the aim is to improve ecosystem functions and services of species-rich road verges and green infrastructure through evidence-based control and monitoring of Garden Lupine at the landscape scale.

During this seminar, I’m going to introduce the background for the project, and talk about what has been done and what I am planning to do in the next years.

The seminar will be streamed live over zoom on Tuesday 26th April at 13.15 CET. The zoom link for the seminar is https://kau-se.zoom.us/my/kaubiology. You are welcome

Garden Lupine (Lupinus polyphyllus) native to North America has been classified as an invasive species in Sweden. In Sweden, they are mainly distributed in road verges. A group of researchers at Karlstad University led by Prof. Lutz Eckstein has been tasked with finding efficient management strategies to control their spread. The research aims at finding out when the garden lupine can be controlled most effectively. Watch Prof. Lutz Eckstein and doctoral student Elin Blomqvist talk about this research in a video interview as they collect and examine lupines at different stages of development.

Watch the full video here : https://tinyurl.com/mbnjhmh

Professor Lutz Eckstein is senior author in a new paper in the journal Applied Vegetation Science led by Zahed Shakeri (Kassel University, Germany). Livestock grazing is still an important disturbance in many forest ecosystems of the world. While studies have addressed the general impact of different grazing and light intensities on temperate forest ecosystems, little is known about how the combination of these two factors can affect the species pool and functional diversity of temperate forests.

The authors studied vegetation and environmental data of 104 relevés from Oriental beech forests (Fagus orientalis) of northern Iran. These were assigned to four groups based on their light and grazing intensities. Non-metric multidimensional scaling was used to analyze vegetation compositional relationships among groups. They used nine functional traits related to growth, reproduction, and survival for a total of 147 plant species. Redundancy analysis of community-weighted means was used to determine the response of single traits to disturbance and environmental variables. Both light and grazing intensities significantly affected species pools, single traits, and functional divergence. Suites of trait attributes including hemicryptophytes, therophytes, grass-like, hygromorphic leaves, insect-pollinated, rhizomes, and runner plants were associated with high-light sites. In closed-canopy (low-light) sites, the strong filtering effect of shade resulted in suites of trait attributes including taller plants, macrophanerophytes, scleromorphic leaves, simple leaves, and berry fruits. While high-light sites had a larger species pool, they exhibited less functional diversity. Cattle grazing can mediate the filtering effect of light, and increase functional diversity in both low-light and high-light sites. Conservation measures in this region should acknowledge that moderate traditional cattle grazing combined with individual-tree and group-tree selection in these forests may maintain or even enhance functional diversity in these valuable ecosystems.

Read more about the paper here: https://doi.org/10.1111/avsc.12592.

Professor Lutz Eckstein is co-author in a new paper in the journal Applied Vegetation Science led by Yves Klinger (Justus-Liebig-University Giessen, Germany). The authors assessed the role of mowing machinery and endozoochory by migratory sheep as dispersal vectors in semi-natural grasslands by comparing the species compositions and traits of species found in the vectors to the regional above-ground vegetation and soil seed bank. Plant material from mowers (n = 12 from one date) and dung samples from migratory sheep (n = 39 from 13 dates) were collected and the dispersed plant species were determined using the emergence method. We compared the species compositions to the regional above-ground vegetation and seed bank using non-metric multidimensional scaling (NMDS) and indicator species analysis. Furthermore, we compared functional traits of the dispersed species to traits of non-dispersed species of the regional species pools by calculating log-response ratios and performing metaregressions.

Sheep in the Rhön Mountains. Photo by Yves Klinger.

We found that mower samples were more similar to the above-ground vegetation whereas dung samples were more similar to the seed bank. Mowers and sheep endozoochory favored the dispersal of species with different traits and phenologies. Species with small seed sizes were prevalent in both vectors. Mowers were less selective concerning most traits, but favored high-growing grasses such as Alopecurus pratensis and Trisetum flavescens. Sheep dung samples contained less grasses and more palatable species, such as Urtica dioica.

Log-response ratios dispersal vectors vs species pools of sheep vs above-ground. LDMC = Leaf Dry Mass Content, EIV N = Ellenberg Indicator Value for Nutrients. Zero indicates the mean value of the non-dispersed species from the respective species pool, bars show mean log-response ratios ± confidence intervals. Figure is part of Figure 3 in the paper.

Sheep endozoochory and mowing machinery are complementary dispersal vectors favoring species with differing functional traits. Sheep endozoochory enables dispersal of species that have unfavorable traits (e.g. low releasing heights) or phenologies for dispersal by mowing machinery. To ensure the dispersal of a high number of plant species in semi-natural grasslands, the interplay of different vectors should be considered.

Read more about the paper here: https://doi.org/10.1111/avsc.12579.

Lutz Eckstein, professor at Karlstad University, is involved in two recently published papers, studying the effects of invasive Garden Lupine (Lupinus polyphyllus) on vegetation and seed bank of mountain meadow plant communities.

The first paper together with Wiebke Hansen (first author), Julia Wollny, Annette Otte and Kristin Ludewig, published in the journal Biological Invasions (https://doi.org/10.1007/s10530-020-02371-w), found that the invasion of Garden Lupine homogenizes vegetation composition. The similarity among plots increased with increasing lupine cover in three different vegetation types. L. polyphyllus affected species diversity in terms of richness and effective species number but in rather complex ways, i.e. plots with low to intermediate lupine cover had higher species diversity than control plots. Probably, the invasion though Garden Lupine is linked to significant species turnover. A very clear effect was found for community-weighted means of species trait. In all three vegetation types studied, the canopy height of the community increased with increasing lupine cover, whereas especially in the low-productive Nardus grasslands, leaf dry matter content decreased and specific leaf area increased. Thus, the Garden Lupine shifted the suite of community traits towards more competitive trait values. This may lead to overall more productive plant communities from which rare, low-growing herbs and grasses will disappear.

Germination experiment from the seed bank study in the paper published in Restoration Ecology. Photo: Kristin Ludewig

The second paper with Kristin Ludewig (first author), Wiebke Hansen, Yves Klinger, and Annette Otte, published in the journal Restoration Ecology (https://doi.org/10.1111/rec.13311), analyzed the effects of increasing cover of Garden Lupineon the seed bank of mountain meadows, and the potential of the seed bank of these stands for active restoration of mountain meadows in terms of species composition and number. The authors conducted a seed bank analysis on 84 plots with increasing cover of L. polyphyllus in three mountain-meadow types of the Rhön Biosphere Reserve, Germany. Seedlings from 119 species germinated from the seed bank samples, including 17 Red List species but only a few seedlings of L. polyphyllus. While the influence of L. polyphyllus on the current vegetation was visible, no effects on the seed bank were apparent. L. polyphyllus had no influence on total seed density, seed density of typical mountain-meadow species, or species numbers in the seed bank. Only the seeds of the Red List species were significantly related to the cover of L. polyphyllus. The authors conclude that the seed bank offers potential for active restoration of species-rich mountain meadows, but species absent from the seed bank have to be added by other measures.

Kristin Ludewig, Wiebke Hansen and Yves Klinger will presents these and other results from a large restoration project in the UNESCO Rhön Biosphere Reserve at the RivEM week.

On Tuesday 14 January, Jacqueline Hoppenreijs, RivEM PhD-student, will give a seminar titled “Rooting for riparian vegetation”. Jacqueline will present her plans for her PhD project during the seminar, with emphasis on her fieldwork this summer.

The seminar starts at 13:15 in room 5F416 at Karlstad University. Everyone who wants to are welcome to attend the seminar.

 

Jacqueline doing fieldwork

 

Riparian plants in the growroom at Karlstad University

Jacqueline Hoppenreijs recently joined the NRRV research group. Here she writes about her previous work and what she intends to do as a PhD student at Karlstad University:

Hej! I’m Jacqueline Hoppenreijs and I recently started my PhD in the NRRV group at Karlstad University. During my MSc, which I did at the Department of Environmental Science at Radboud University in Nijmegen (the Netherlands) and the Department of Ecology at SLU Uppsala, I worked on different species groups: plants, birds and insects and wrote two theses. The first one, with fellow student Bas van Lith, explored possibilities for bird population restoration on the Indonesian island of Java, using historical sources on bird population development and land use change over the course of a century. During the second one, I studied the importance of different man-made habitat types for pollinators in Sweden, over the course of a season.

 

Bas and I birdwatching in Rancaekek, by Fachmi Azhar Aji

 

Despite studying quite different time frames and taxa, biodiversity, ecosystem functioning and conservation have been recurring themes. Coming from the overpopulated Netherlands, I find myself very interested in the interface of human society and nature, and more specifically nature restoration, conservation efforts and their ethical aspects.

As a junior researcher at the Department of Animal Ecology & Physiology at Radboud University, I dove a bit deeper in the influence that human actions can have on the natural world. I worked in Rob Leuven’s group to identify the potential risks of invasive (alien) species in horticulture, biological control and food forestry.

As from April 2019, I’m working with Lutz Eckstein and Lovisa Lind. We’re focusing on both fundamental and applied aspects of plant ecology and I’m looking forward to unravel the mechanisms that drive plant dispersal and community composition in boreal riparian zones. Next to that, I’m excited to be part of an active education environment and the passionate group of researchers that forms the NRRV, and can’t wait to meet the rest of Karlstad’s community!

 

Vegetation sampling on Omey Island, by Joop Schaminée

Viola elatior and the two habitats used in the study: early successional floodplain meadows and late successional alluvian woodlands. Photos: Benjamin Schulz.

Benjamin Schulz, Walter Durka, Jiří Danihelka and Lutz Eckstein recently published the research paper “Differential role of a persistent seed bank for genetic variation in early vs. late successional stages” in the scientific journal PLOS ONE. In the abstract, the authors write:

“Persistent seed banks are predicted to have an important impact on population genetic processes by increasing effective population size and storing past genetic diversity. Accordingly, persistent seed banks may buffer genetic effects of disturbance, fragmentation and/or selection. However, empirical studies surveying the relationship between aboveground and seed bank genetics under changing environments are scarce. Here, we compared genetic variation of aboveground and seed bank cohorts in 15 populations of the partially cleistogamous Viola elatior in two contrasting early and late successional habitats characterized by strong differences in light-availability and declining population size. Using AFLP markers, we found significantly higher aboveground than seed bank genetic diversity in early successional meadow but not in late successional woodland habitats. Moreover, individually, three of eight woodland populations even showed higher seed bank than aboveground diversity. Genetic differentiation among populations was very strong (фST = 0.8), but overall no significant differentiation could be detected between above ground and seed bank cohorts. Small scale spatial genetic structure was generally pronounced but was much stronger in meadow (Sp-statistic: aboveground: 0.60, seed bank: 0.32) than in woodland habitats (aboveground: 0.11; seed bank: 0.03). Our findings indicate that relative seed bank diversity (i.e. compared to aboveground diversity) increases with ongoing succession and despite decreasing population size. As corroborated by markedly lower small-scale genetic structure in late successional habitats, we suggest that the observed changes in relative seed bank diversity are driven by an increase of outcrossing rates. Persistent seed banks in Viola elatior hence will counteract effects of drift and selection, and assure a higher chance for the species’ long term persistence, particularly maintaining genetic variation in declining populations of late successional habitats and thus enhancing success rates of population recovery after disturbance events.”

Read the paper here!