Micro forests: small forests with a big impact

A 100 year old forest in 10 years? What may not sound particularly desirable to us, it is for the so-called micro forests: rapid aging in the shortest possible time. These man-made forests, which are also known as Tiny Forests or Miywaki Forests, are planted very densely and have a high level of biodiversity.

What is behind the Micro forests?

This method of forest planting was originally developed by the Japanese botanist and plant expert named Dr. Akira Miyawaki. He found that, under certain conditions, a forest can be preserved within 10 years that has the characteristics of a 100-year-old forest. That not only sounds impressive, but it is! Especially when you see all the benefits these small forests bring. Micro forests based on the Miyawaki method are 30 times denser, 100 times richer in biodiversity, reduce 30 times more noise and air pollution and have up to 30 times better CO2 absorption compared to traditional tree plantings. In addition, they ensure a significantly better local microclimate and offer a living space for insects, mammals and songbirds.

Keep cool!

Trees have been shown to cool the ambient temperature by storing CO2. They are therefore one of the most effective measures against climate change. So let’s plant trees!

A real game changer for cities

Especially with regard to climate change and, coupled with this, the rising temperatures, micro forests are a great and useful concept, especially for cities. On the one hand, micro forests require very little space. On the other hand, the quality of life of the residents is significantly improved by cooling the climate, improving air quality and the positive influence of forests on mental health. At present, mainly solitary trees are being planted in the cities, which create shade, but are otherwise far from being able to compete with a micro forest (although both require a similarly large area).

It was clear to us that we, as a climate hotel and green oasis in the middle of Erlangen,  also plant a micro-forest! And so it happened that a part of the hotel garden was chosen to become home to a micro forest. First, however, some precautions had to be taken that the future forest has the perfect conditions. For Microforests the soil structure is very important and more complex. Therefore, the concept is generally more suitable for small areas.

First, the top (humus) layer of soil had to be removed and remains of roots removed. Below that lies the quite sandy subsoil, which is loamy in the deeper layers. About 30 cm of soil was removed (which of course is used elsewhere in the garden). At a depth of 60 cm to 150 cm, a trench was then partially excavated for a gravel pack. This underground ditch, which is about eight meters long and filled with gravel, serves as a retention system. This means that the rainwater from the hotel roof flows in here and can slowly seep away and be absorbed by the trees.

In addition to the retention system, which is primarily intended for heavy rainfall, a non-pressurized drip irrigation system has been laid underground throughout the micro forest. The special Perl hose is used to ensure that the roots of the trees grow directly around it and can be optimally supplied with water. You can water easily and without pressure using gravity alone – without a garden pump or electricity.

The next step was to rebuild the important substrate layer for the trees. A more “fatter”, more nutrient-rich soil was used. This was “emaciated” with some sand and finally mixed with straw. The straw ensures that the compact soil remains permeable to air and looser, while still being able to retain moisture. For example, if the soil is sandy, the water just flows through it and is lost.

All trees have now been planted in this layer. Some of these were native species and some were trees that are particularly well adapted to future climatic conditions. Overall, the trees were planted very densely, which deviates from the usual afforestation method.

However, this creates a special challenge: very many plants have to share the available nutrients. Therefore, another layer of wood chips comes to the bottom. This 10-15 cm high layer has two very important functions. On the one hand, the wood chips prevent too many other shrubs, grasses or weeds from growing and, on the other hand, the layer has an extremely insulating effect. Even if it is dry and hot for longer periods, this layer ensures that it is still moist and cooler underneath.

In this way, fungi can also spread better with their mycelium. In nature, the network of fungal mycelia plays a very important role in nutrient transport and conversion. In the forest, you usually only see the fruiting bodies, which we can then harvest as mushrooms.

Most of the work is done now and the micro forest will need around 2-3 more years of maintenance in the form of regular watering and pruning before it can be left entirely to its own devices. Now we watch our own small hotel forest grow and look forward to all the new roommates and positive aspects that it brings with it!

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