Although not equally in all ecosystems, regional plant development is influenced by the global climate. By examining more than 300,000 European vegetation plots, geobotanists at Martin Luther University Halle-Wittenberg (MLU) came to this conclusion. They come to the conclusion that it is impossible to make a general prediction about how climate change would affect Earth’s vegetation; instead, the impacts will largely rely on the local circumstances and the environment being studied. Their findings were published in Nature Communications.
Ever since Alexander von Humboldt’s voyages of exploration, it has been clear that the characteristics of plants depend heavily on the Earth’s climate zones. For example, giant trees and plants with enormous leaves can be found in tropical rainforests, while desert or subarctic vegetation grows lower to the ground and has smaller leaves to withstand drought or cold temperatures.
These zones are shifting as a result of climate change, which raises concerns about how altered precipitation patterns and greater temperatures could affect the diversity of plant species in a particular area.
“Studies have found relatively weak correlations between global climate gradients and the characteristics of local plant communities,” explains Dr. Stephan Kambach, a research associate in the Department of Geobotany at MLU. “It is possible that the global effects are being obscured by local factors such as plant composition, soil conditions, microclimate, groundwater levels or human land use.”
We were able to show that the global climate is definitely a significant indicator for local plant communities. However, if we want to prepare for changing climate conditions, especially in agriculture and forestry, we have to look very closely at habitats with similar floristic compositions, a common evolutionary history, and comparable environmental conditions.
Dr. Stephan Kambach
The researchers from Halle have gathered more than 300,000 vegetation plots from all around Europe that contain complete information on the main plant species and climate data in order to understand this phenomenon. This has been done as part of the Biodiversa program “FeedBaCks.”
The raw data were taken from the CHELSA climate database and the European Vegetation Archive (EVA), which includes more than 1.7 million vegetation plots of nearly 14,000 plant species.
“First, we examined nine main types of habitats, for example forests, moorlands or wetlands,” explains Kambach. “Then we subdivided these habitats into two additional sub-levels, for example deciduous forests on the second level and poplar floodplain forests on the third level.”
In order to compare the vegetation in the different habitats, four key vegetation characteristics were defined: height of growth, leaf area, root length and seed mass.
In order to examine how climate variables, particularly temperature and precipitation, affect vegetation, Stephan Kambach employed linear regression. A statistical technique called linear regression can be used to identify significant relationships between affecting and target variables.
The analysis revealed some surprising results: When all vegetation types are considered, climate is a significant predictor of plant characteristics. Plants tend to grow higher, generate more seed mass, and have longer roots in the Mediterranean region and along Europe’s coasts, although they have smaller leaves overall.
A look at the individual habitats, however, reveals exceptions: In forests, for example, plant height decreases as temperatures increase, in wetlands the leaf area is getting larger, and in moorlands the roots are getting shorter.
“Here the opposing influences between the trends at the global and local levels become apparent,” explains Professor Helge Bruelheide, who heads the FeedBaCks project at MLU and is also a member of the German Center for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig.
“In southern regions, growth is generally facilitated by a higher light intensity and longer growing seasons, however decreased availability of water can lead to the opposite effect in certain habitats. In contrast, low levels of precipitation seem to have little effect on wetlands.”
The more one “zooms in” on the habitats, the harder it is to make generalizations about climate effects.
“When it comes to leaf area and root length, climate appears to have a strong effect in more tightly defined habitats,” says Kambach. “But what we see in the main habitat types is not necessarily reflected in the subtypes.”
For example, the analysis revealed that the mean height of growth in grasslands increases towards the Mediterranean, but not in seasonally wet meadows. The situation is similar in wetlands: Here, plants grow taller as temperatures increase, but this is not the case in exposed riparian zones.
“We were able to show that the global climate is definitely a significant indicator for local plant communities,” states Kambach.
“However, if we want to prepare for changing climate conditions, especially in agriculture and forestry, we have to look very closely at habitats with similar floristic compositions, a common evolutionary history, and comparable environmental conditions.”
