Archive for category: Plant knowledge

In the summertime, you can find clover in meadows, along paths, or in fields. It comes in red, yellow, or white varieties. However, the diversity of clover species is much greater than many people realize. In this story, we want to introduce you to six different representatives of the plant genus Trifolium, which are widespread in large parts of Europe. We hope this encourages you to take a closer look the next time you come across a “clover” on your next walk. This story is the result of a school internship, and we would like to extend our sincere thanks to Maike for her research and writing.

Red meadow clover (Trifolium pratense)
Red meadow clover or red clover Trifolium pratense can be found everywhere: in gardens, meadows, forests and along roadsides and field edges. Thanks to its attractive red to purple flowers, which are full of nectar, the red meadow clover is sought out by many butterflies, such as the lady butterfly, as a food source and also as a caterpillar plant. It flowers from April to October, forming a multi-flowered spherical inflorescence covered by the uppermost stem leaves. This type of clover is rich in protein, making it a popular food plant. Additionally, red meadow clover is edible for humans and has earned a reputation as a medicinal plant. It has been used internally and externally for a variety of ailments since the 11th century.

White clover (Trifolium repens)
White clover Trifolium repens, like all the other species presented here, belongs to the legume family and the papilionaceous subfamily. Its flowers and leaves are similar to those of red clover, except that the flowers have a (eponymous) white color. Each of the 40-80 individual flowers in the inflorescence produces 3 to 4 seeds, which are egg-shaped to roundish and orange-yellow. The four-leaf clovers, which are considered lucky charms, are rarely found among wild plants. However, there is a cultivated variety for gardens and balcony boxes, the “four-leaved chocolate clover” (Trifolium repens ‘Quadrifolium Purpureum’), which is easy to care for and is predominantly four-leaved.

Small clover (Trifolium dubium)
This species is widespread throughout Europe. It can be found in meadows, pastures or garden lawns. Its yellow flower turns brownish when the fruit ripens. The small clover Trifolium dubium is considered a forage plant and is often visited by insects such as bumblebees for pollination. If you only take a quick glance, you could confuse it with Medicago lupulina – in this case, identification with Flora Incognita or examination of the calyx will help. The calyx of the small clover is glabrous, while that of the hop clover is hairy.

Field clover (Trifolium campestre)
This member of the family has small, yellowish, shell-like flowers. Known as “butterfly flowers with a folding mechanism,” they have areas that absorb ultraviolet light and others that reflect it. This makes them appear two-colored to pollinators such as honeybees, flies, or butterflies. The field clover Trifolium campestre thrives on sandy, loamy, or stony soils, as well as on meager meadows, where it is considered a fodder plant. It avoids nitrogen-rich subsoils, making it an indicator plant for nitrogen-poor soil.

Mountain clover (Trifolium montanum)
Mountain clover Trifolium montanum is found throughout Europe, but can also climb to high altitudes – which gave it its name. For example, it can be found on the Jöchelspitze in Tyrol at an altitude of 2226 m, and in Valais in Switzerland it has been observed at 2560 m. Due to its white to yellowish-white flower color and the typical round shape of the inflorescences, it is easy to confuse with the more common white clover. However, the mountain clover grows more upright and has a hairy stem and longer, lanceolate leaves. Its habitat requirements are also different. White clover is a generalist, but mountain clover grows on semi-arid and dry grassland in warm locations with clayey-humus soils.

Incarnate clover (Trifolium incarnatum)
The incarnate clover Trifolium incarnatum is also known as Italian clover, as its original distribution area covers the Mediterranean region, including Italy. Today, however, it can also be found in Germany, mainly in areas without spring frosts, as it does not tolerate them well; and it is cultivated as a popular forage plant in large parts of Europe. The leaves of the incarnate clover are very large for a clover species, but its most striking feature is probably its flower color. The deep purple-red flower heads, which are elongated spikes in this species, appear from May to August.

This article was featured as a story in the Flora Incognita app in 2024. In the plant identification app, you will always find exciting information about plants, ecology, species knowledge, as well as tips and tricks for plant identification. Take a look!

Biodiversity – The Series

The three main aspects of biodiversity are species diversity, the genetic diversity of a species and the diversity of habitats in a region. We cover all those aspects in dedicated articles. In this one, we take a closer look at how important it is to have multiple habitats in a given area.

What does habitat diversity mean?

Habitat diversity is a metric of how many different habitats are present in a given area. For example, an area where a naturally flowing stream separates a woodland fringe from a meadow may have a high structural diversity. A large arable field without hedges or wildflower strips, on the other hand, does not have a high diversity of habitats. A high diversity of habitats automatically increases the species diversity of the area, as each of these biotopes has its own biocoenosis and therefore a single area can be colonized by more species.

Loss of habitats

Humans bear the main responsibility for the destruction of habitats through the use of natural resources, air, light and water pollution, noise pollution, intensive agriculture, industrial production and the progressive urbanization of landscapes. Other influential human activities include mining, deforestation and trawling. Eutrophication, the excessive input of nitrogen and phosphorus into ecosystems and the atmosphere, has a global impact. In the long term, this nutrient input leads to nutrient-poor habitats losing their unique and species-rich character and becoming increasingly similar to other locations.

However, abiotic environmental factors can also (indirectly) contribute to the destruction of habitats. These include geological processes such as volcanism, climate change, and the spread of invasive species.

Invasive species take over habitats

Habitat destruction in an area can lead to a shift in local biodiversity from a mix of generalists and specialists to a population consisting mainly of generalists. Invasive species are often generalists because they can survive in a much wider variety of habitats than specialists. If these invasive species, which are particularly prolific, colonize ever larger habitats in an area, there is less and less room for the few specialists originally native to the area. As a result, the so-called extinction threshold of the specialists shifts ever further into a fatal direction – and the probability of their extinction increases.

Loss of biodiversity

Habitat destruction is the biggest driver of species loss and the loss of genetic diversity within species. And this is not just about the loss of large and popular animals such as the giant panda. Species such as nematodes, mites, earthworms, fungi and bacteria carry out many of the processes that are essential to human life, such as purifying air and water, and they too disappear when their habitats are destroyed. At a higher level, plants not only provide structural diversity and protection against erosion, but also energy and nutrients, which are then processed by other creatures in the food chain.

Example: Deadwood

A “well-tended and tidy” (managed) forest is often one from which wood is harvested before it can die. However, this means that the forest habitat is missing something that was originally an integral part and has been able to develop and optimize itself over thousands of years – a hotspot of biodiversity: under the bark of dead trees, starch, sugar, vitamins, proteins, amino acids and cellulose are waiting to be decomposed by longhorn beetles and bark beetles, wood wasps and thousands of often highly specialized insects and fungi. Their bore dust, excrement and moulting residues attract new wood colonizers – by the way, different ones in lying than in standing dead wood. Bats, owls and dormice use dead wood as a hibernation camp or roost, while other organisms – plants, fungi, woodlice, mites and worms – complete the decomposition process. What remains is a large amount of humus, the perfect basis for new growth.

Biodiversity

The example of deadwood shows impressively that countless habitats and processes have already been changed and destroyed so quickly by humans that entire groups of organisms have become extinct or their survival is acutely threatened. However, knowledge of the interrelationships and daily efforts to preserve and restore habitats can make the difference between preserving a diversity of habitats, of species and the diversity within these species in your own town, village or garden.

This article was featured as a story in the Flora-Incognita app in spring 2024. In this plant identification app, you can find exciting information about plants, ecology, species knowledge, and tips and tricks for plant identification. Check it out!

Biodiversity – The Series

The three main aspects of biodiversity are species diversity, the genetic diversity of a species and the diversity of habitats in a region. We cover all those aspects in dedicated articles. In this one, we take a closer look at the aspect of species diversity.

Species diversity

The term species diversity describes the number of biological species in a given area. This applies to small areas as well as large ones: a single tree in the Amazon, an entire mountain range, a political state, or even just a grid cell in a city. Typically, the species diversity of such an area is divided into specific groups such as plants (or just trees), mammals, fish, insects – depending on the question or topic.

How many species are there?

In 2006, around 2 million species were scientifically described. This contrasts with estimates of 5 to 20 million species that actually exist worldwide. It is very difficult to give precise figures for these two, as different groups of organisms have different criteria for species delimitation, and modern classification methods also include genetic information. There are also a large number of synonyms, and most species are very small and live in areas that are not easy to reach. Nevertheless, around 12-13,000 new species are scientifically described every year.

Why is species diversity important?

Nature is crucial for our survival as it provides us with important ecosystem services such as food, medicines, water regulation and recreational opportunities. It also helps to regulate the climate, and each species plays a unique and important role. The absence of a species can lead to the disruption of complex ecological cycles. For example, the extinction of insect species can have a negative impact on birds that feed on these insects and on the pollination of plants (including crops).

What threatens species diversity?

First and foremost is the destruction of habitats through construction, clearing, or modification, e.g., through intensification of soil cultivation. Many species-rich habitats are nutrient-poor, as a few dominant species spread quickly on nutrient-rich sites. The input of nitrogen and phosphorus from pollutants poses a threat to these habitats. Finally, invasive species can also have a lasting impact on existing ecosystems by disrupting the complex interactions between the species that occur there and successfully displacing established species. Above all these factors is climate change, which is altering many established processes so rapidly that the adaptability of many species cannot keep pace.

How can species diversity be protected?

Restoring or maintaining diverse habitats is the most important measure for preserving species diversity – or at least slowing its decline. Examples include restoring floodplain landscapes along rivers, allowing standing and lying deadwood in forests, thinning dry grasslands, extensive year-round grazing, flowering strips with native wild herbs and shrubs on agricultural land and stopping the drainage of moors. But our own actions can also have an influence: Wild corners in the garden, partially mowing of meadows, use of peat-free soil, participation in work to remove invasive plants or political and educational work are valuable building blocks for the preservation of species diversity.

This article was featured as a story in the Flora-Incognita app in spring 2024. In this plant identification app, you can find exciting information about plants, ecology, species knowledge, and tips and tricks for plant identification. Check it out!

In winter or in cold habitats such as high mountains, an optimal flower temperature is important for successful reproduction. Some plants can actively produce heat in their flowers, such as Helleborus foetidus, using yeast bacteria in the nectar (Herrera and Pozo, 2010). But this is the exception. For most plants in cold regions (or early bloomers), the more heat they can absorb from the environment, or at least not lose, the better. In this story you will learn what influence characteristics such as shape, colour, pubescence or orientation to the sun have on the temperature in the flower.

Bells and discs
Have you ever wondered why many early bloomers have bell-shaped flowers? The answer is that bells collect more heat than disc-shaped flowers. Hanging bells can absorb heat from the ground radiation and so the temperature inside the flower lies 3-11 °C above the ambient temperature (Kevan, 1989). Upright bells, such as gentians, bundle the sun’s rays when they fall at a certain angle. In disc-shaped flowers, the reproductive organs are directly exposed to the environment and are located in the centre, where most of the incoming light is reflected by the flower. But the petals also play a role. In one experiment, the excess temperature in Saxifraga oppositifolia flowers was reduced by 70% compared to the surrounding area after removing the petals (Kevan, 1970).

Micro-greenhouses
Another successful strategy is the formation of “micro-greenhouses”. These are, for example, bubble-shaped structures made of translucent bracts, as in the yellow rattle (Rhinanthus minor), or sepals, as in Physalis. These filter light in the UV range, but allow longer wavelengths to pass through, which heats the air inside. Similar to flowers, hollow stems can also have a heating effect if the heat trapped in the stem leads to an increase in internal temperature (Kevan et al. 2018, 2019). This can promote the development of the flower bud immediately above it.

Orientation towards the sun (heliotropism)
During the course of the day, some plants permanently orientate their flowers so that they face the sun. In cold regions in particular, this leads to effective warming of the flower. This can have advantages for the plant, for example through increased temperatures in the reproductive organs, heavier seeds and more visits from pollinators. Many experiments have already tried to demonstrate the added value of heliotropism, but not always successfully. (Van der Kooi, 2019).

Colour
Darker colours can absorb more solar radiation. This can be converted into heat, which can increase the temperature of the flower. In a series of experiments with Plantago, a close relationship was found between the colour of the flower-bearing inflorescence and its temperature. Individuals developing at low temperatures produced darker panicles that were 0.2-2.6 °C warmer in direct sunlight than the comparison group (Anderson et al., 2013). Another study found that purple-coloured flowers of Ranunculus glacialis were warmer and produced more seeds than white-coloured flowers of the same species (Ida & Totland, 2014). However, there are also studies in which the colour of the flower has no influence on the flower temperature (Van der Kooi, 2019). Further studies are needed to better understand the relationship between flower colour, temperature and reproductive capacity.

Opening and closing
The opening and closing of flowers through petal movement is widespread throughout the plant world. In particular, cup- or disc-shaped flowering species protect themselves from external factors such as light, moisture or temperature in this way. Opening and closing can take several minutes or hours, depending on the species. It is assumed that closing the flower protects the pollen from precipitation (washing out, damage) or drying out, which increases its viability. There are various experiments that have investigated the influence of flower closure on the temperature inside the flower: For example, if the bracts of Tulipa iliensis close at cool temperatures, a more constant temperature is maintained inside the flower (Abdusalam and Tan, 2014).

Hairs
The pubescence of flowers is probably important for maintaining flower temperature, but in contrast to leaf pubescence, this has been little studied to date. Plant species that grow in high-altitude, cold regions sometimes develop thick leaf pubescence. This creates an insulating boundary layer to the neighbouring cold air mass, which reduces heat loss (Meinzer and Goldstein, 1985). The pubescence of the flowers can have a similar insulating effect as in the example of willow catkins: In Alaska, it was investigated that it can be 15-25 °C inside willow catkins at an air temperature of 0 °C. If the woolly hairs were removed, the internal temperatures in the catkins fell by around 60% (Krog, 1955).

References:
• Herrera CM, Pozo MI. 2010. Nectar yeasts warm the flowers of a winter-blooming plant. Proceedings of the Royal Society of London B 277: 1827–1834.
• Kevan PG. 1989. Thermoregulation in arctic insects and flowers: adaptation and co-adaptation in behaviour, anatomy, and physiology. Thermal Physiology 1: 747–753.
• Kevan PG, Nunes-Silva P, Sudarsan R. 2018. Short communication: thermal regimes in hollow stems of herbaceous plants—concepts and models. International Journal of Biometeorology 62: 2057–2062.
• Kevan PG, Tikhmenev EA, Nunes-Silva P. 2019. Temperatures within flowers and stems: possible roles in plant reproduction in the north. Bulletin of the NorthEastern Science Centre of the Russian Academy of Sciences, Magadan, Russia 1: 38–47.
• Casper J van der Kooi, Peter G Kevan, Matthew H Koski, The thermal ecology of flowers, Annals of Botany, Volume 124, Issue 3, 16 August 2019, Pages 343–353,
• Anderson ER, Lovin ME, Richter SJ, Lacey EP. 2013. Multiple Plantago species (Plantaginaceae) modify floral reflectance and color in response to thermal change. American Journal of Botany 100: 2485–2493.
• Ida TY, Totland Ø. 2014. Heating effect by perianth retention on developing achenes and implications for seed production in the alpine herb Ranunculus glacialis. Alpine Botany 124: 37–47.
• Abdusalam A, Tan D-Y. 2014. Contribution of temporal floral closure to reproductive success of the spring-flowering Tulipa iliensis. Journal of Systematics and Evolution 52: 186–194.
• Meinzer F, Goldstein G. 1985. Some consequences of leaf pubescence in the Andean giant rosette plant Espeletia timotensis. Ecology 66: 512–520.
• Krog J. 1955. Notes on temperature measurements indicative of special organization in arctic and subarctic plants for utilization of radiated heat from the sun. Physiologia Plantarum 8: 836–839.
• Kevan PG. 1970. High arctic insect-flower relations: the inter-relationships of arthropods and flowers at Lake Hazen, Ellesmere Island, N.W.T., Canada. PhD Thesis, University of Alberta, Canada.

This article was featured as a story in the Flora-Incognita app in winter 2024. In this plant identification app, you can find exciting information about plants, ecology, and species knowledge, as well as tips and tricks for plant identification. Check it out!

Magical Autumn
Green, yellow, red, brown leaves in all transitional phases currently call for long forest walks, providing atmospheric nature experiences and creative inspirations. However, there’s nothing magical behind this: decomposition and substance transport are responsible for the transformation. The aging process is known as senescence, and the eventual leaf fall is termed abscission. Let’s take a closer look at both:

Senescence – the Last Chapter of Phenology in the Year

Genetically controlled and dependent on available energy, leaves age in autumn. They take in less and less CO2 and eventually cease photosynthesis altogether. When the leaves fall to the ground, this is measurable through remote sensing. The so-called “browning,” the brownish appearance of the ground beneath the bare tree, marks the end of the phenological year. But why do deciduous trees shed their leaves?

Leaf Shedding – Threefold Genius

Leaves evaporate large amounts of water, around 300 to 600 liters per square meter of leaf area per year in a beech tree, for example. Roots absorb the necessary water from the soil, which is not possible when it’s frozen. The tree would dry out. By shedding leaves, this flow of water is stopped, and the tree survives the winter unscathed. But there are two more important advantages that come with leaf fall: the environmental toxins accumulated and stored in the leaves are disposed of, and bare trees withstand snow loads better.

The Chemistry of Autumn Colors

The vibrant colors of the autumn forest are present in the leaves throughout the year but masked by green chlorophyll! When chloroplasts, the storage sites of chlorophyll, are transformed into gerontoplasts within cells, chlorophyll breaks down, revealing other pigments. Carotenoids appear yellow-orange, and anthocyanins bring out red tones – incidentally, as a stress response to excessive sunlight. The red pigments act as a shield against intense sunlight and ensure that chlorophyll breakdown occurs in dying leaves even on cold, sunny autumn days.

How Does Leaf Fall Work?

When exactly a leaf falls from a branch depends on various factors. There is a genetic component for each species, but also site characteristics such as altitude, temperature, day length, and wind play a role. Decreasing availability of light and warmth activates phytohormones, and at the end of the leaf stalk, an anatomical process of change occurs: a separation tissue forms where middle lamellae, cell walls, or entire cells dissolve. Eventually, the leaf’s own weight is enough for it to fall to the ground.

This article was featured as a story in the Flora-Incognita app in autumn 2023. In the app, you can find exciting information about plants, ecology, species knowledge, as well as tips and tricks for plant identification. Why not take a look!