Revealing a unique historic dataset on vegetation composition of Swiss grasslands or developing a passion for dusty vegetation records

The post is provided by Susanne Riedel, Jürgen Dengler, Felix Herzog and Stefan Widmer

Friedrich Stebler and Carl Schröter in front of the hut on the Fürstenalp, where they spend a lot of time, exfoliating off 67 vegetation sods (http://doi.org/10.3932/ethz-a-000068526).

This post refers to the article The Historic Square Foot Dataset – Outstanding small-scale richness in Swiss grasslands around the year 1900 by Susanne Riedel and colleagues published in the Journal of Vegetation Science (https://doi.org/10.1111/jvs.13208)

Interested in how grasslands in Central Europe looked more than 100 years ago, where we stumbled upon a new world record for vascular plant diversity in grasslands and what offers us manifold options for studies on long-term changes in grassland biodiversity and productivity? You will find out here in a minute.

A stack of old vegetation survey sheets laying on the table of one of the authors’ office companions and waiting for a sparking project idea, only triggered a sneezing fit and pity for the person who had the charge to make use of this yellowed paper. Fortunately, the pile of papers migrated to another institute, where they realised the value of these surveys at once and initiated the submission of a project to the Swiss National Fund to repeat the historic surveys. Side note: meanwhile, becoming wiser, the above-mentioned author developed a passion for dusty vegetation surveys and applied for joining the project.

As a first milestone of the resulting Square Foot Project, we present its treasure and centrepiece in this article: the rare collection of 580 grassland records originating from the turn of the 20th century. Containing vegetation-plot records (relevés), covering the whole elevational gradient of Swiss grasslands and sampled with a highly standardised method, this is to our knowledge the largest dataset of this kind and age.

Susanne Riedel, Stefan Widmer and Manuel Babbi, who conducted most of the resampling in 2021 and 2022.

Let’s have a look at the story behind these data. In the late 19th century, researchers Dr. Friedrich Gottlieb Stebler and Prof. Dr. Carl Schröter aimed to increase the productivity of Swiss meadows and pastures. As a prerequisite, they systematically collected knowledge on the natural composition of the Swiss grassland. They wanted to study not only the influence of external abiotic factors on the composition of the stands, but also the natural change in meadows and pastures over time and the influence of improved management like irrigation, fertilisation, drainage and type of use. The main work of the researchers consisted in cutting out a square-foot sized sod (30 cm x 30 cm) of a homogeneous grassland stand and taking it to the laboratory. There, they separated the shoots, sorted, counted and identified all vascular plant species and finally weighed the dried fractures.

Around half of these records have been published in a series of articles in an agricultural yearbook at that time. The original sheets remained undetected by posterity in a cupboard until the removal of the same, due to renovation works, which flushed it to daylight and to the hands of one of the authors. Fascinated by this, he set all levers to motion to digitise the sheets. He and his team provided great preparatory work, when pinpointing the records around 15 years ago, based on the information on the record sheets. At that time, the historical maps were only available in print. Another group transcripted the vegetation part and converted the original nomenclature to the one used in Flora Helvetica, 4th edition, 2001.

Spatial distribution of all historic plots in Switzerland with hotspots in the region of Zurich (157 plots) in the North-East and on the Fürstenalp (67 plots) in the East (map from the original article).

Thanks to these inputs, at the beginning of the Square Foot Project in 2021, the project team could directly “fly” to the right spot on the digitised map. Their work consisted in drawing the potential perimeter of where each sod had been taken as precisely as possible. Concerning the vegetation part, we only had to check all records for mistakes, where the sum of the weight percentages differed from 100 as well as all records where the absolute weight had been indicated. At last, we updated the nomenclature for our analysis and all elements of the present paper were ready.

We show that the mean small-scale species richness in grasslands was higher than today, with a mean of nearly 20 species in 0.09 m2 (GrassPlot Diversity Explorer). Moreover, five of the historic plots reached or exceeded the mark of 43 species (present-day world record, Wilson et al. 2012), with a maximum of 47 species. In the historical data, we could not find a significant variation in species richness with elevation, differing from today’s hump-shaped relationship.

Are you curious (after reading the whole paper), how species richness and vegetation composition changed in the meantime? In the Square Foot Project, we resampled most of the plots. Now, we are digging for patterns and drivers of epochal changes. Stay tuned for the first results to be published soon.

One of the historic recording sheets. It is not always easy to decipher the handwriting. The species have not only been weighed as a whole, but they have been sorted by seedling, sterile and fertile shoots. An incredible effort!

Brief personal summaries:

Susanne Riedel is a PhD student at the agricultural research institution Agroscope in Zurich and the University of Zurich, Switzerland. Her research interest is understanding mechanisms how diversity in grasslands arose and can be sustained or promoted with an adequate agricultural policy.

Jürgen Dengler is a professor of vegetation ecology at the Zurich University of Applied Sciences (ZHAW), Wädenswil, Switzerland, and PI of the Square Foot Project. He works in vegetation ecology, macroecology, conservation biology and ecoinformatics. Currently, he intensively deals with quantifying biodiversity changes through vegetation resurveys, describing maroecological patterns of biodiversity and neophyte impact as well as developing broad-scale consistent vegetation classification systems, with a focus on natural and semi-natural grasslands of the Palaearctic.

Felix Herzog, PhD is an agronomist and landscape ecologist. He has worked in interdisciplinary research for more than 25 years on projects in Switzerland, Germany, Europe and beyond. Since 2000, he has been a research group leader at Agroscope. Research interests comprise the interactions between agricultural practices and the environment, agricultural landscapes and biodiversity, the evaluation of ecosystem services, and novel production systems such as agroforestry.

Stefan Widmer is a PhD student at the Zurich University of Applied Sciences (ZHAW), Wädenswil and the University of Zurich, Switzerland. His broad interest in the field of vegetation ecology includes the effect of different land use and conservation measures on diversity.