Deadwood: A hotbed of life
Deadwood includes dead trees. There is standing dead wood, in which the tree is not removed, and lying dead wood, which lies on the earth and rots. In a primeval forest in Europe, up to 30% of the wood consists of dead trees, in an economic forest mostly only a tenth of it. The removal destroys valuable habitats for the entire food chain.
Life in the dead
Dead wood provides the basis for a variety of organisms, most of which rely on a certain phase of decay and a certain type of wood. These include, in particular, around 1,350 beetles and several hundred large mushrooms that live on dead trees until they have completely become minerals. These species are interdependent: insects infect the wood with fungal spores, other insects eat the fungi, let their larvae grow in them or live in them themselves.
Bees and wasps
For example, most of the approximately 1000 German bees and wasps depend on dead wood as their livelihood. They build their nests in the holes, cracks and troughs that develop during decay, here their larvae grow, here wasps catch the insects from which they feed. Wild bees, wasps and hornets prefer upright and dead tree stumps.
In addition to the insects that eat the wood, other insects settle as second settlers in the caves and passageways that the wood eaters create.
Bark, crown wood, tree mulch
There is not even a species spectrum in dead wood, but diverse communities of flora and fauna: bark, crown wood, tree mulch, tree hollows, burned areas, lying or standing dead wood and furthermore beech, pine etc. These are all their own habitats with specialized animals and Plants. Depending on light exposure, moisture, fungal and insect infestation, wood volume and degree of decomposition, certain types come.
Spruce and oak bucks
The beetles called spruce bucks only live on coniferous wood, the disc bucks on dried coniferous wood, the rams on hardwood. One of them, the alpine goat, only settles on mushroomed beech wood. Names like oakbuck already refer to the corresponding food. Fire beetles in turn live under the bark of dry dead wood, their larvae hunt bark beetles, which are also dependent on wood.
Wood ants build their nests in hollow tree trunks, horse ants live in dead coniferous and hardwood. No wonder that many of these species are now endangered species: black woodpeckers such as wrynecks, stag beetles, the larvae of which live on the roots of rotten oaks, elms and fruit trees, the carpenter bees, gnawing the passages in the wood or the beetles.
The same applies to giant wood wasps, which lay their eggs in the wood and vaccinate them with fungal spores, or the giant hatching wasp, which lays its eggs in the larvae of the wood wasps.
Every fourth species of beetle in Germany lives on deadwood, and the proportion of wood-eating beetles among the extremely endangered beetle species is high.
Food for others
Small invertebrates provide the livelihood for amphibians, reptiles, fish and small mammals. They include dung mosquitoes, hair gnats, and midges, the larvae of which develop in wood. This also applies to rompers, whose larvae eat tree fungi, wooden flies hunt larvae and worms.
Amphibians, reptiles, birds and mammals
Vertebrates build nests in dead wood and find their food here. Woodpeckers in particular specialize in insect larvae that live in them. They hammer their nesting cavities into rotten wood, not always dead wood - although this, when standing upright, is ideal for woodpecker caves. The three-toed woodpecker builds its nests in rotten trunks, gray and green woodpeckers lay their caves in sick and dead wood at different heights.
The woodpeckers' tree hollows in turn use other species such as rough-footed, sparrow and tawny owl, hollow pigeon, squirrel, bilche, pine marten, Bechstein bat, fringed bat, water bat or large noctule.
Lying dead wood is a habitat for pond, mountain, string and comb newts, fire salamanders, toads, forest and sand lizards, slow crawls, adder, ring and snake snakes. In terms of water, it offers habitat for the almost extinct European pond turtle, which likes to sunbathe on tree trunks lying in the water.
Fungi (and bacteria) decompose dead wood, and this process forms the basis for complex communities. Tinder fungus or Hallimasch feed on it and produce the humus, which in turn is the basis for the growth of various plants, especially for seedlings of trees. Dead trees regenerate the forest.
If the dead wood lies on the earth, a special microclimate is created. Wood conducts little heat and has a dark surface. That is why the temperature stays warmer than the air when the air cools down in winter. In addition, the wood protects against overheating and drying out in summer.
For this reason, it is an important habitat for amphibians such as fire salamanders, all newts and toads whose skin needs moisture and who cannot tolerate extreme heat.
Deadwood in rivers and streams
The major rivers in Germany are largely straightened. Without this clear cut on the river bank, dead wood is inseparably part of the river landscape and even determines the flow speed and water level: logs in the water slow down the flow, debris sticks to the wood, and islands form.
Dead wood slows down the erosion of the banks, sediments are deposited on it, which prevents the river from digging into it. The water pushes to the sides through the traffic jam, the rivers meander. It creates a variety of structures in the flowing water habitat.
The wood provides habitats such as still water zones and hiding places that attract many rare animal species today: crayfish. Mussels and fish. Branches and treetops with many branches in particular create spawning grounds for fish and amphibians.
A habitat that has become rare today is largely characterized by dead wood: the riparian forest. Quarry forests and swamps are also habitats that would not exist without dead and dead trees.
"Clean up" and destroy biodiversity
Unfortunately, the economic use of forests and the creation of parks for recreation traditionally means removing dead wood. The Germans "love" the forest and it belongs to the history of the German mentality like the sea to the British, but the forest for hiking should be "like an orderly garden". Dead trees are considered "untidy".
The ecological importance of these is not reflected in the state nature conservation laws. Only in Saxony are “cave-rich individual trees” and “dead wood-rich old wood islands” explicitly protected.
The economic forest in Germany is not a forest that is subject to the natural process of growing, maturing and dying. The trees are felled on almost the entire area outside of national parks and nature reserves before they can die and dead wood forms.
As a result of rising heating costs, more and more people are turning to wood stoves, with the result that wood that has been uneconomical in the meantime can also be sold lucratively: mushroom wood, broken wood or branch cut.
In forestry and allotment gardens, despite all ecological facts, measures were taken to remove the basis from "pests". To this day, this madness can still be found in many gardener colonies: allotment garden magazines publish articles in the same issue about insect death with building instructions for insect hotels and at the same time call for the removal of the dead wood, as this is a "breeding ground for pests".
This thinking comes from a time when the forest and garden were thought of as a system controlled by the forester or gardener. Just as the "gardeners" used the lethal injection to destroy every naturally grown wild plant and used pesticides to kill ants, beetles and mosquitoes, so the foresters removed every decaying tree stump and every branch that a storm had torn to the ground.
The result was an extremely species-poor forest, which had only the name in common with a grown mixed forest. Even more: the cleared spruce monocultures with no under or dead wood meant that forest pests in particular were able to multiply extremely.
The dense canopy of the spruces ensured that hardly any deciduous trees could grow, hardly any snow or rain came to the ground and flowers, herbs, shrubs and other plants disappeared, along with the animals to whom they offered food and habitat.
So while the monocultures and the removal of dead wood should prevent pest infestation, the opposite happened. Wood eaters specialized in exclusively planted trees such as the bark beetle were able to multiply explosively in this land of milk and honey; secondly, their natural predators were now missing.
The deadwood strategy
It was only slowly that knowledge came to the fore that dead trees are also necessary for a stable commercial forest. For example, the federal government's biodiversity strategy today recommends that a large proportion of those are left in the forest.
However, this is not of a legal character, but consumers can help: A high proportion of dead wood is an essential criterion for certifying wood as sustainable. The FSC seal is only available if it stays in the forest.
Gardener against "ugliness"
Urban gardeners usually remove dead wood from the roadside and from city parks because it is considered unaesthetic. Another reason to clear it out is traffic safety. If a tree falls on a traffic route, it is the owner's fault. This applies to private owners as well as to municipalities.
However, this does not apply to the "open corridor" or "unused land" and also not to the "existing forest". The owners are not liable here. In Germany in particular, gardeners and forest owners who leave the old wood behind are often still regarded as “untidy”, an assumption that every natural gardener has probably heard of before. A quote from conservationist Konrad Guenther from 1910 shows a German practice in the forest:
"How unappealing is the sight of transparent, undergrowthless forests, in which the trees may have been planted according to the cord and now stand in a straight line and at reasonable intervals like a regiment of soldiers."
The rural economy mainly used the forest for firewood and construction wood. Leaving dead wood was a waste. 19th-century sources show that farmers only entered the forests near their village when timber was identified.
Madness and garbage disposal
For traditional garden owners, however, the idea of a “natural idyll” goes hand in hand with the delusion of order. Many even reject bark mulch in their front yard as a litter because it looks “dirty”. For others, a garden is only a garden when they have torn out all the tree stumps and have cut the branches to the recycling center.
It doesn't matter for these cleanliness freaks whether the sloe, blackberry and elder in the neighbour's dead wood corner comply with the garden regulations according to which edible fruit and vegetables are to be planted in the allotment garden, but not the hydrangea or the English lawn. They also don't recognize the bad joke when they set up insect hotels and hang bird nesting boxes while stealing the livelihood of birds and insects at the same time.
The idea of a “decent forest” that does not smell of mildew, in which no trunk rots in the water and no ants crawl out of a dead tree stump, unfortunately still means that private gardeners and municipalities empty parks, city forests and fallow land from dead wood clearing and giving endangered animal and plant species no chance.
What to do?
Do you have your own property, fallow land, a farm, just a front garden? In order to protect and restore the dead wood habitat across the board, forestry and agriculture have to forego cultivation on part of the area. Resettlement by specialized beetles and specialized insects is hardly possible on your own square meters.
But you can do something on a small scale. Tree-brood breeders, who usually head for dead trees, find a substitute in nesting boxes for tits, garden redtails, starlings etc. Perforated bricks and reeds, clay slabs and wooden blocks with drilled tubes in different sizes offer insects the shelter that they otherwise find in decayed wood.
Use dead wood - don't throw it away
But the deadwood itself is best. You shouldn't expect miracles here either. Specialists who are set up for the biochemistry of rotting beech or oak can hardly thrive in the branch cut that occurs in the garden. Species with a broader range of life can, however, be a suitable substitute in the garden.
For example, if you saw off a tree, leave the stump standing and drill holes for insects, or stack cut branches on a pile of brushwood. Is that too messy for them? Then you can bring the wood into the garden structure in many ways, be it as a Benjes hedge, as a raised bed, as a scaffold or bird house.
A Benjes hedge
A Benjes hedge is a hedge made up of branches, twigs and trunks. The brothers Heinrich and Hermann Benjes popularized this nature reserve hedge; Farmers, however, have been planting such hedges for centuries for practical reasons.
For such a hedge, you first lay posts or even thick branches in the ground, two at the same height, and, depending on the width of the hedge, between 50 cm and one meter away. These should be about 2 meters apart. Such a hedge can be four, but also 100 meters long.
Now stack your branch cut half a meter or meter between the posts, ideally so that the long branches are delimited by the posts and the small wood does not fall out of the boundary. With sufficient branch cutting, you will achieve a stable border with your neighbors, wind and privacy protection, but above all, a valuable biotope in the long term.
You can also connect the individual posts on the outside with ropes and hold the branches. Caution: Do not layer the branches too closely. The purpose of a Benjes hedge is for the seeds to germinate in the green waste in the hedge. If the branches are too dense, you will not enjoy a sea of flowers.
A tip: If you take branches from the garden trees, especially fruit trees or willow, you can also weave the "pillars" into the hedge. This then supports itself.
This hedge grows: when the branches are cut again, you can simply put it in the Benjes hedge. The hedge initially has two advantages: First, it costs you nothing, except maybe the post. Secondly, you don't need any care at first.
A wild hedge
You can, like some farmers and some natural gardeners, let the hedge overgrow: shrubs, wildflowers and herbs settle on their own, birds and the wind distribute the seeds, and within a few years the dead wood has become a living structure.
Depending on the other circumstances, i.e. pH value of the soil, stony, sandy, moist, sunny or shady, certain plants settle. The blackberry is one of the pioneers you can count on with certainty. Hawthorn and rose hips also spread birds with their droppings. Competitive plants such as nettles and goldenrods come naturally - both are good food for insects.
A growth process
A Benjes hedge develops from a dead wood to a scrub hedge, so shoots form, this results in a herb layer and later an individual plant. After several years, everything grows into a field hedge. You do not need to fertilize the dead wood hedge or provide it with other supplies, because bacteria and fungi decompose the wood, which creates humus, which in turn promotes hedge growth.
Plants for the Benjes hedge
If you have brought soil into the hedge, daisies, chamomile, yarrow, thistles or nettles will also spread quickly. After the first year at the latest, you can systematically plant the hedge with perennials, wildflowers and bushes. In the natural garden, you should choose native plants that serve as food for insects and birds.
Do you want a green wall? Then plant wild wine, wild or rambler roses, ivy, hops or clematis on the hedge. You will cover them within a few years. Climbing flowering plants such as nasturtiums, winches and wakes are also suitable.
The hedges are a paradise for berry bushes that find a hold on them. Blueberries, raspberries, gooseberries, goji and currants thrive here splendidly.
Ideally, place the hedge in front of a row of trees or plant trees behind it. Bushes that are suitable for the area around them and at the same time represent valuable food plants for birds are bird cherry, elderberry, sloe, dogwood, honeysuckle, viburnum, rock pear, ornamental quince, crab apple or priest's hat.
Plants that colonize wood and solid humus, i.e. ferns and mosses, are suitable as area cover plants.
For the spaces in front of the hedge and possible humus or compost soil that they bring into the hedge, we recommend the following: blue stars, crocuses, daffodils, wild tulips, allium, March cups, lily-of-the-valley, wood anemones and in summer seed bands with cornflowers, wild carrot, Mullein or borage.
Wild perennials around the Benjes hedge quickly ensure that the hedge no longer looks like a “pile of wood”, but like a flower hedge. Suitable include: Hollyhocks, clary sage, bluebells, bedstraw, pharmacist roses, mallow, foxglove and checkerboard flowers.
There is also an honorary award, soapwort, elf flower, carnation, widow flower, snake head, goat clover, corn weed, lady's mantle, stonecrop or snapdragon.
Kitchen and medicinal herbs also feel comfortable in the protection of the hedge: mint such as lemon balm, St. John's wort and chives, tarragon, marjoram and lovage.
An animal paradise
A Benjes hedge in the open field offers animals a corridor that does not cross large areas. In the garden, the amphibians, birds and mammals find shelter, breeding grounds and food that disappear from the cleared city gardens:
Wren, hedge brown, common warbler, blackbird and song thrush, robin, fitis, zilpzalp and garden redstart. Mammals such as mice, seven- like garden sleepers, dormouse, hedgehogs and shrews come, common toads, pond and mountain newts, wild bees, wild bumblebees, wasps, beetles and lacewings.
What do you need to look out for?
If you plant the hedge in the garden, the soil here is usually rich in nutrients. This favors fast-growing perennials, especially those of goldenrod or nettle, which slow-growing plants such as dogwood take away the light. Therefore, you should rely on specimens that are about 50-100 cm long for certain shrubs that you absolutely want to have in the hedge.
In the second part of our series “Deadwood - hotbed of life” you will learn how to use the wood, compost and leaves to create a raised bed or a hedge border. (Dr. Utz Anhalt)
Author and source information
This text corresponds to the specifications of the medical literature, medical guidelines and current studies and has been checked by medical doctors.
Dr. phil. Utz Anhalt, Barbara Schindewolf-Lensch
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