Which plant species grow where, alongside which others - and why?
An international team of scientists has produced the world’s first global database of vegetation plots, which contains over 1.1 million complete lists of plant species abundances from field surveys across all terrestrial ecosystems.
The research is published in the scientific journal Nature Ecology & Evolution. It was led by Martin Luther University Halle-Wittenberg (MLU) and the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, with scientists from the University of Nottingham’s School of Geography being the leading UK scientists on the project.
The key area of the work, according to Dr Richard Field from the University of Nottingham, is that the team has produced the first global view of plant communities. He said: “Until now, our understanding of plant strategies and their fit to environment has come from comparing individual species, or from particular parts of the world.”
All plants face the same basic challenges, whether they are small grasses, shrubs or trees. “For example, they have to find an efficient way to conduct photosynthesis in order to obtain the energy they need. At the same time, they compete with neighbouring plants for limited resources in the soil, like water and nutrients,” explains Professor Helge Bruelheide from the Institute of Biology / Geobotany at MLU and co-director of iDiv.
Currently around 390,000 plant species are known to science. Over time, species have developed different traits and trait combinations in reaction to the living and non-living environments at their locations. These include plant size and the thickness and chemical make-up of leaves. These properties are also known as functional plant traits.
Until now, researchers have primarily investigated different combinations of these functional traits from the perspective of individual plant species. “In reality, however, plant species rarely occur alone; plants live in communities,” says Bruelheide. Therefore, vegetation plot databases are needed that contain data on all of the plants growing at specific locations.
Up until now there has been no database of databases, to compile and harmonise all the different datasets that exist. As a result, the "sPlot" initiative was launched at the iDiv research centre to develop and set up the first global vegetation plot database, unifying and merging the existing datasets.
"sPlot" currently contains 23.6 million records of 55,000 plant species’ occurrences in 1.1 million vegetation plots from every continent, information that has been collected over decades by thousands of researchers from all over the world. The database, which is described in a separate paper accepted in the last week for publication in the Journal of Vegetation Science, could help better predict the consequences of global climate change.
The scientists in the research group combined this massive dataset with the world's largest database of plant traits, which is called “TRY” and is also an iDiv database platform. They tested, for instance, to what extent global factors influence the functional traits of plant communities.
Contrary to current opinion, they found that temperature and precipitation play a relatively limited role. “Surprisingly, these two macro-factors are not so important. Our analysis shows, for example, that plant communities are not consistently characterised by thinner leaves as the temperature increases - from the Arctic to the tropical rainforest,” says Bruelheide. Instead, the researchers found a close tie between climate variables and the phosphorus supply in the leaves, reflected in the ratio between nitrogen and phosphorus content in the leaf, which is an indicator of plant nutritional status. For example, the longer the growing season, the lower the phosphorus supply - this also affects leaf thickness.
Local land use and the interaction of the different plants at a specific location have a much greater impact on the functional traits of plant communities. These findings caution against forecasting future plant production on the basis only of simplistic temperature-precipitation models.
The study published in Nature Ecology & Evolution is the first in a series of upcoming papers by the "sPlot" consortium. Being available on request to other scientists, the “sPlot” database offers unprecedented opportunities to tackle numerous biodiversity questions at the global scale, including issues pertaining to the distribution of non-native plant species and the similarities and differences of plant communities across world regions.
Dr Franziska Schrodt from the University of Nottingham sums up the excitement: “Having this global database of plant abundance and functional traits gives us better insights into how plants relate to their environment than ever before. This will allow us to improve our understanding of how and why certain species of plants grow together and where their growth is limited by environmental conditions, such as soil nutrients. It will also help us to understand how plant communities might change with climate change in the future. It is great to see the global patterns emerging from the data for the first time.”
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