More evidence that Europe’s ancient landscapes were open woodlands: Oak, hazel and yew were abundant
A new study finds that the disturbance-demanding plant species oak, hazel and yew were abundant in Europe’s forests before modern humans arrived, strengthening the argument that ancient vegetation was not the shady closed-canopy forests often imagined
Aarhus University
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Artist's rendering of open woodland in ancient temperate Europe.
view moreCredit: Brennan Stokkermans
In 2023 a research group from Aarhus University in Denmark found that light woodland and open vegetation dominated Europe’s temperate forests before Homo sapiens.
In a new study, recently published in Journal of Ecology, they take a closer look at the composition of these forests.
The results show that European wildwoods were rich in hazel, oak, and yew – species thriving in dynamic semi-open ecosystems rather than in classic dense forests.
“Often, we imagine established forests as dense, closed spaces where light-demanding species like oak and short-statured species like hazel and yew were rare. Our results challenge this view, showing that oak, hazel, and yew consistently thrived in these ancient woodlands, further supporting a picture of a semi-open, mosaic-like vegetation,” explains Dr Elena Pearce, lead author and postdoc at the DNRF Center for Ecological Dynamics in a Novel Biosphere (ECONOVO), Department of Biology, Aarhus University.
Plants as detectives
The team looked to oak, hazel, and yew as "detectives" of ancient forest life, revealing clues about how past woodlands were structured.
For instance, hazel shows stronger pollen and flower production in sunlit areas, oak resprouts vigorously after browsing, and yew, while somewhat shade-tolerant, requires semi-open conditions to avoid competition from taller trees. In fact, all three taxa tend to decline in tall, shady forests. Yew is also extremely sensitive to fire but can coexist with large megafauna species such as horses, oxen, or likely even larger animals, due to its high toxicity, which deters extensive browsing.
Large herbivores as nature’s landscape architects
The researchers used the REVEALS model for pollen-based reconstructions to analyse the prevalence of oak, hazel, and yew in two key periods: the Last Interglacial (129,000-116,000 years ago) and the early-to-mid Holocene (8700-5700 years ago). See fact box.
By further investigating forest composition, they revealed that open and semi-open vegetation supported diverse species combinations that would have struggled in closed-canopy environments.
Rather than natural fires or climate regimes causing openness, these new results suggest that large herbivores played a leading role in maintaining open and semi-open landscapes. Yew’s sensitivity to fire highlights this, as it would have struggled to thrive in fire-prone systems yet persisted in ancient woodlands where herbivores likely kept forests dynamic and open.
“These species tell us that ancient forests were not uniformly dominated by tall shade-giving trees but must have been composed by a dynamic mix of open, semi-open and closed areas, providing a high diversity of habitats,” says Professor Jens-Christian Svenning, senior author and director of ECONOVO.
Modern nature management inspired by the past
The implications go beyond historical ecology. Semi-open woodlands may have played a critical role in Europe’s biodiversity, creating habitats for species adapted to a variety of conditions.
“Our findings provide a new perspective on ancient ecosystems and highlight the need to maintain semi-open woodlands today. These environments support a diverse mix of plants and animals, and understanding them can help to inform rewilding efforts,” says Dr Pearce.
The study also highlights how open, dynamic woodlands might contribute to climate resilience and biodiversity gains.
“As we face global challenges like warming temperatures, climatic extreme events and rising tree pest invasions, creating dynamic, varied woodland mosaics is likely to provide more robust ecosystems functions and biodiversity benefits than conventional dense forest plantings,” says Professor Svenning.
Semi-open forests allow for diverse plant species, which in turn provide essential functions like carbon storage, pollinator habitats, and broader biodiversity maintenance. Reforestation strategies that recreate these semi-open, dynamic woodland structures likely better align with future climatic and ecological challenges, guiding sustainable forest management in Europe and beyond.
Quercus robur (English Oak) in an open grassland. Oak trees are fire-tolerant and benefit from canopy openings driven by fire or large grazers - and they were abundant in the ancient European woodlands.
Credit
Jens-Christian Svenning
Fact:
You can read about the REVEALS model (Regional Estimates of Vegetation Abundance from Large Sites) in a research article here: https://journals.sagepub.com/doi/abs/10.1177/0959683607075837
Journal
Journal of Ecology
Subject of Research
Not applicable
Article Title
Higher abundance of disturbance-favoured trees and shrubs in European temperate woodlands prior to the late-Quaternary extinction of megafauna
Tree growth conditions on the tundra in Finnmark and Svalbard
Data from the weather stations of the Climate-Ecological Observatory for Arctic Tundra (COAT) indicate that the tundra in Svalbard and East Finnmark has experienced conditions conducive to tree growth over the past two summers.
UiT The Arctic University of Norway
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COAT's weather stations, even those located far beyond today's forest distribution on the Varanger Peninsula (green areas on the map), have experienced temperatures above the 10-degree threshold necessary for tree growth in recent summers.
view moreCredit: COAT
Last year, it attracted significant attention when Longyearbyen, for the first time, recorded an average July temperature exceeding 10°C, surpassing the classical criterion for polar climate, which typically precludes tree growth. This summer has brought new record-high temperatures to both Svalbard and East Finnmark. In 2024, COAT's weather stations on the most barren mountain peaks of the Varanger Peninsula at 70oN in East Finnmark —far from the existing tree line—recorded temperatures 3-4 degrees above this temperature threshold.
Not Random
Weather normally varies significantly from year to year, so records could appear randomly. However, based on the normal variation over the last 30 years (1991-2020), the temperatures recorded in August 2024 in Vardø (Eastern Finnmark) would randomly occur only twice in 1,000 years, and in Longyearbyen, twice in 10 million years. This strongly suggests that the record-high summer temperatures of the past two years are not due to chance but are a result of ongoing climate changes in the Arctic.
More Precise Climatic Criteria for Tree Growth
While the classic 10-degree rule generally works well for Arctic and alpine tree lines, recent studies have shown that a combination of the length of the growing season and average temperature provides more precise criteria (Paulsen and Körner 2014). Specifically, the growing season must consist of at least 94 snow-free days with daily temperatures above 0.9°C, and the average temperature over this season must be at least 6.4°C. If these criteria are met over many years, the climate is suitable for tree growth.
In both 2023 and 2024, these criteria were met at all COAT weather stations on the Varanger Peninsula, as well as some stations on Svalbard. At Reinhaugen/Boazoaivi—located in the high mountains at 470 meters above sea level and deep within the low-Arctic tundra of the Varanger Peninsula—the growing season lasted 104 days with an average temperature of 12.0°C. The Nedre Sassendalen station on the high-Arctic tundra of Svalbard had a 102-day growing season with an average temperature of 7.3°C.
How Quickly Can Forest Replace Tundra?
Summers that meet the criteria for tree growth are expected to eventually lead to continuous forest. However, the establishment of forests on the tundra can take a long time. Studies of past climate changes have shown that it can take many centuries from when the climate is warm enough for tree growth until full-fledged forest ecosystems establish themselves. There are several reasons for such mismatch between climate changes and ecosystem responses. The increase of other plants, which respond more quickly to climate changes, can create poor conditions for tree seedlings. Outbreaks of organisms that directly damage trees can actually cause the Arctic tree line to temporarily retreat—not advance—in a warmer climate. COAT's documentation of increasing amounts of crowberry (Tuomi et al. 2024) and the effects of large moth outbreaks are examples of such processes already active in Finnmark (Vindstad et al. 2019).
Important Ecosystem-Wide Monitoring
As rapid climate changes now occurring in the Arctic can lead to unstable ecosystems with surprising properties, it is crucial to closely monitor developments using "ecosystem-wide observation systems" like COAT (Ims and Yoccoz 2017). In addition to weather stations, COAT has established an extensive network of automatic sensors and manual measurements that continuously document how the entire ecosystem responds to global warming. There is close collaboration between researchers and managers of biological diversity and natural resources so that COAT can provide research-based preparedness to handle climate and nature crises in the northern regions.
Average temperature for August at Svalbard Airport each year since 1900. The last two summers (2023 and 2024) have been exceptionally warm.
Credit
COAT
The COAT weather station at Reinhaugen/Boazoaivi – located 470 meters above sea level – with very sparse vegetation deep within the low-Arctic tundra on the Varanger Peninsula.
Credit
Valeriy Ivanov / Norwegian Institute for Nature Research
Forest killed by moths
Across large areas in East Finnmark, the forest has been severely damaged by moths over the last two decades.
Credit
Jakob Iglhaut
Find weather and climate data from COAT and MET weather stations here:
Seklima at the Meteorological Institute: https://seklima.met.no/observations/
Reinhaugen on Yr: https://www.yr.no/nb/historikk/graf/1-323916/Norge/Finnmark/Nesseby/Reinhaugen
Nedre Sassendalen on Yr: https://www.yr.no/nb/historikk/graf/5-99882/Norge/Svalbard/Nedre%20Sassendalen
Tuomi, M. et al. 2024. https://doi.org/10.1038/s43247-024-01451-2
Vindstad, O.P.L. et al. 2019: https://doi.org/10.1111/1365-2745.13093
Ims, R.A. and Yoccoz. N.G. 2017. Ecosystem-based monitoring in the age of rapid climate change and new technologies. Current Opinions in Sustainability Science 29: 170-176. doi.org/10.1016/j.cosust.2018.01.003
Facing the wind: How trees behave across various forest settings and weather events
Researchers in Japan and France identify two primary tree movement patterns that help them survive high winds and prevent damage
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Forest configuration, defined by tree density and spacing, affects trees’ resistance against powerful winds. In this study, the thinned plot experienced tree failures due to Typhoon Trami, while the dense plot showed no damage. This finding highlights the need for foresters to adopt safe thinning practices.
view moreCredit: Kana Kamimura from Shinshu University
Destructive winds during storms and cyclones often cause tree failures, especially through uprooting and stem breakage. However, how trees respond to wind under various forest configurations and weather conditions remains unclear. A recent study on Cryptomeria japonica plots shows that trees dissipate wind energy by switching between two swaying behaviors at specific wind speeds, offering insights that may help in improved forest management to minimize damage caused by storms.
Extreme weather events, such as tropical and extratropical cyclones and tornadoes, can cause widespread damage to forests, leading to environmental and financial losses. When trees fall during these storms, ecosystems might be disrupted, increasing forest management costs. As climate change worsens, severe storms are expected to become more frequent, making it crucial to understand how forests respond to wind stress.
Grasping the mechanisms behind tree failure is key to developing strategies for mitigation. While previous studies have explored how trees react to wind, it is unclear whether these responses remain consistent across different forest configurations—characterized by tree spacing and density—and weather conditions.
In this vein, a team of researchers led by Associate Professor Kana Kamimura from the School of Science and Technology at Shinshu University, Japan, investigated tree movements under various forest configurations and weather conditions, including how trees resist winds. The research team included Kazuki Nanko, Asako Matsumoto, and Saneyoshi Ueno from the Forestry and Forest Products Research Institute, Japan, and Barry Gardiner from the University of Freiburg, Germany, and the Institut Européen de la Forêt Cultivée, France. This paper was made available online on August 27, 2024, and was published on November 1, 2024, in Volume 571 of Forest Ecology and Management.
Explaining their motivation behind the study, Prof. Kamimura says, “Several techniques have been developed to predict wind damage. However, they largely depend on empirical data and parameters, and overlook how wind damage occurs. Our research aims to shed light on how winds directly impact trees and how trees reduce the stress from winds to survive.”
To achieve this, researchers set up two experimental plots of Cryptomeria japonica trees, commonly known as the Japanese cedar, in November 2017 in the experimental forests operated by the Forestry and Forest Products Research Institute, Kasumigaura City, Japan. In the first plot, P-100 consisted of 3,000 trees per hectare, creating a dense forest. In the second plot, P-50, half of the trees were removed for this research, leaving 1,500 trees per hectare to mimic thinning practices. Over two years, the team monitored 24 trees in the dense plot and 12 in the thinned plot, using trunk-mounted sensors to track tree sway during various wind conditions. The monitoring period included multiple typhoons, such as Typhoon Trami, in 2018, which caused significant damage to the thinned plot.
The researchers found that cedar trees exhibit two distinct swaying patterns depending on wind speed. In light winds, the trees swayed at around 2 to 2.3 cycles per second, with their branches absorbing much of the wind energy, protecting the trunks and roots from wind stress. However, at higher wind speeds, the trees shifted to a slower swaying pattern of 0.2 to 0.5 cycles per second. In this phase, the whole tree swayed together, transferring force across the trunk and roots, increasing the probability of breakage or uprooting.
Interestingly, the transition between these two swaying modes occurred at different wind speeds, depending on the forest density. In the dense plot, the trees switched patterns at wind speeds between 1.79 and 7.44 meters per second. In contrast, in the thinned plot, the transition occurred at slightly lower wind speeds, ranging from 1.57 to 5.63 meters per second.
Using an uprooted tree as a reference, researchers assessed the resistance to damage in the thinned P-50 over a 10-minute period during Typhoon Trami. They found that the actual resistance was only 48% of the expected resistance estimated through controlled tree-pulling experiments.
Prof. Kamimura elaborates, “The 52% difference between actual and expected resistance values was likely due to the roots weakening because of strong winds, even before the winds became more severe. This root fatigue occurred because the trees moved more due to less support from nearby trees and more wind penetrating the plot.” This also explains why the trees in the dense P-100 were not damaged during Typhoon Trami.
This study offers valuable insights for balancing thinning with wind resistance in forest management to support sustainable forestry practices, and help forests withstand extreme climate changes. While thinning promotes tree growth, it can also make forests more vulnerable to storms, especially soon after thinning. Prof. Kamimura concludes, "With more frequent storms in a changing climate, forest management practices must adapt to maintain resilience.”
Tree anchorage against wind connects to the characteristics of the root-soil plate, which can be observed during the tree-pulling experiments. This study explores the mechanism behind trees responding to varying wind speeds during storms and cyclones. The researchers provide new insights into the resistance of trees to natural calamities that may improve forest management strategies against storms and cyclones.
Credit
Kana Kamimura from Shinshu University
About Shinshu University
Shinshu University is a national university founded in 1949 and located nestling under the Japanese Alps in Nagano, known for its stunning natural landscapes. Our motto, "Powered by Nature—strengthening our network with society and applying nature to create innovative solutions for a better tomorrow," reflects the mission of fostering promising creative professionals and deepening the collaborative relationship with local communities, which leads to our contribution to regional development by innovation in various fields. We are working on providing solutions for building a sustainable society through interdisciplinary research fields: material science (carbon, fiber, and composites), biomedical science (for intractable diseases and preventive medicine) and mountain science, and aiming to boost research and innovation capability through collaborative projects with distinguished researchers from the world. For more information, visit https://www.shinshu-u.ac.jp/english/ or follow us on X (Twitter) @ShinshuUni for our latest news.
About Associate Professor Kana Kamimura from Shinshu University
Dr. Kana Kamimura is an Associate Professor in the Department of Agricultural and Life Sciences at Shinshu University, Japan. Her research focuses on wind damage in forests based on spatial, biomechanistic, and statistical approaches. Currently, she is leading a project of exploring alternative approaches to understanding trees’ dynamic behavior in forests. With over 6,290 reads and 813 citations to her name, Kamimura has made significant contributions to understanding forest resilience and sustainability. Her work aims to support effective forestry practices in the face of climate change and extreme weather events.
Journal
Forest Ecology and Management
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Energy transfer during tree movement for different wind conditions and forest configurations
Diverse and diverging demands on forests in Germany
Research team analyze biodiversity, ecosystems and economics of enriching beech forests with conifers
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Beech trees in research areas of the DFG Research Training Group 2300 “Enrico”. Beeches usually occur naturally alone without other trees. In this study, the Research Training Group investigated the enrichment with coniferous tree species and the ecological and economic consequences.
view moreCredit: Jan Schick
Forests provide biodiversity, ecosystem functions, income and much more. How can these diverse and seemingly diverging demands be met? An international research team led by the University of Göttingen addressed this question by analysing the effects of enriching beech forests in Germany with commercially valuable native (to mountainous regions of Europe) and non-native conifer species, in this case, the Norway spruce and Douglas fir, respectively. Their study showed that enriching beech forests which naturally have few tree species does not necessarily reduce species richness or ecosystem functioning. In fact, their results showed that there were positive gains at many levels including biodiversity, ecosystems and economic viability, especially for the combination of beech with Douglas fir. The research was published in Science Advances.
The scientists used a unique empirical dataset, taking data from 40 plots of mature European beech forests across the state of Lower Saxony in Germany. The research team combined data from 11 projects, each of which analysed many different research aspects of European beech forests enriched with conifers. These aspects included: seven biodiversity indicators, considering arthropods and birds in the canopy to fungi and creatures in the soil; eight ecosystem functions, including processes involved in nutrient cycling, such as the amount of carbon or nitrogen in the soil or the biomass of the trees aboveground; and six economic functions, such as current and short-term economic return, tree survival and volume of wood in the future. The research gave a unique and comprehensive perspective by integrating these multiple perspectives.
The results showed that mixed forests with beech and Douglas fir have enhanced biodiversity and ecosystem functioning while improving the economic performance compared to monocultures of beech. “There are, of course, major concerns about the potential risks to the environment of introducing non-native species,” explains Dr Larissa Topanotti, “but our research showed it can be possible to do this to the benefit of biodiversity, ecosystems and economics: it was a win-win-win situation. However, the right species for the environment, the spatial scale and the existing forest need to be carefully considered.”
“Increasing the range of species to include more native species and trees species that can adapt to climate change is essential for the future,” explains Dr Nathaly Guerrero-Ramírez. Professor Carola Paul adds: “Our study has contributed to finding compromise solutions to manage the increasingly diverse demands on forests and forest management by society.”
This study was made possible thanks to the German Research Foundation (DFG).
Original publication: Topanotti et al: Enhancing economic multifunctionality without compromising multidiversity and ecosystem multifunctionality via forest enrichment, Science Advances 2024. Doi 10.1126/sciadv.adp6566
Measuring ecosystem functions in the soil and trees on the experimental plots of the DFG Research Training Group 2300 ‘EnriCo: Enrichment of European beech forests with conifers: impacts of functional traits on ecosystem functioning'
s of ecological functions in a beech and Douglas fir mixed forest area on the experimental plots of the DFG Research Training Group 2300 ’EnriCo’
s of ecological functions in a beech and Douglas fir mixed forest area on the experimental plots of the DFG Research Training Group 2300 ’EnriCo’
Credit
Christina Hackmann
Christina Hackmann
Journal
Science Advances
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Enhancing economic multifunctionality without compromising multidiversity and ecosystem multifunctionality via forest enrichment
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